# Patent

## Title
Instruction to compute the distance to a specified memory boundary

## Abstract

A Load Count to Block Boundary instruction is provided that provides a distance from a specified memory address to a specified memory boundary. The memory boundary is a boundary that is not to be crossed in loading data. The boundary may be specified a number of ways, including, but not limited to, a variable value in the instruction text, a fixed instruction text value encoded in the opcode, or a register based boundary; or it may be dynamically determined.

## Background
BACKGROUND
An aspect of the invention relates, in general, to data processing, and in particular, to processing that involves memory boundaries.
Data processing includes various types of processing, including text processing or other types of processing. During data processing, it is often required to perform special handling when the data being processed is nearing a specified memory boundary. Current instructions and/or techniques associated with processing near a memory boundary tend to be inefficient or problematic.
BRIEF SUMMARY
Shortcomings of the prior art are overcome and advantages are provided through the provision of a computer program product for executing a machine instruction. The computer program product includes a computer readable storage medium readable by a processing circuit and storing instructions for execution by the processing circuit for performing a method. The method includes, for instance, obtaining, by a processor, a machine instruction for execution, the machine instruction being defined for computer execution according to a computer architecture, the machine instruction including: at least one opcode field to provide an opcode, the opcode identifying a Load Count to Block Boundary operation; a register field to be used to designate a register, the register comprising a first operand; and at least one field for indicating a location of a second operand, the second operand comprising at least a portion of a block of main memory; and executing the machine instruction, the execution comprising: determining a distance from the location of the second operand to a boundary of the block of main memory; and placing a value representing the distance in the first operand.
Methods and systems relating to one or more aspects of the present invention are also described and claimed herein. Further, services relating to one or more aspects of the present invention are also described and may be claimed herein.
Additional features and advantages are realized through the techniques of the present invention. Other embodiments and aspects of the invention are described in detail herein and are considered a part of the claimed invention.



BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
One or more aspects of the present invention are particularly pointed out and distinctly claimed as examples in the claims at the conclusion of the specification. The foregoing and other objects, features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:
FIG. 1 depicts one example of a computing environment to incorporate and use one or more aspects of the present invention;
FIG. 2A depicts another example of a computing environment to incorporate and use one or more aspects of the present invention;
FIG. 2B depicts further details of the memory of FIG. 2A, in accordance with an aspect of the present invention;
FIG. 3 depicts one embodiment of a format of a Load Count to Block Boundary instruction, in accordance with an aspect of the present invention;
FIG. 4 depicts one embodiment of logic associated with the Load Count to Block Boundary instruction, in accordance with an aspect of the present invention;
FIG. 5A depicts one example of at least a portion of a memory block for which a count is provided, in accordance with an aspect of the present invention;
FIG. 5B depicts one example of a general purpose register including the count, in accordance with an aspect of the present invention;
FIG. 6 depicts one example of a register file, in accordance with an aspect of the present invention;
FIG. 7 depicts one embodiment of a computer program product incorporating one or more aspects of the present invention;
FIG. 8 depicts one embodiment of a host computer system to incorporate and use one or more aspects of the present invention;
FIG. 9 depicts a further example of a computer system to incorporate and use one or more aspects of the present invention;
FIG. 10 depicts another example of a computer system comprising a computer network to incorporate and use one or more aspects of the present invention;
FIG. 11 depicts one embodiment of various elements of a computer system to incorporate and use one or more aspects of the present invention;
FIG. 12A depicts one embodiment of the execution unit of the computer system of FIG. 11 to incorporate and use one or more aspects of the present invention;
FIG. 12B depicts one embodiment of the branch unit of the computer system of FIG. 11 to incorporate and use one or more aspects of the present invention;
FIG. 12C depicts one embodiment of the load/store unit of the computer system of FIG. 11 to incorporate and use one or more aspects of the present invention;
FIG. 13 depicts one embodiment of an emulated host computer system to incorporate and use one or more aspects of the present invention; and
FIGS. 14A-14R depict example vector string instructions and associated components thereof, in accordance with aspects described herein.



DETAILED DESCRIPTION
In accordance with an aspect of the present invention, a capability is provided for determining a distance to a specified memory boundary from a specified location (e.g., memory address). The memory boundary is, for instance, the end of a block of main memory (also referred to herein as main storage). A block of main memory is any block of memory of a specified size. The specified size is also referred to as the boundary of the block. The block of main memory includes data, such as character data, integer data, or any other type of data.
Character data, includes, but is not limited to, alphabetic characters, in any language; numeric digits; punctuation; and/or other symbols. The character data may or may not be strings of data. Associated with character data are standards, examples of which include, but are not limited to, ASCII (American Standard Code for Information Interchange); Unicode, including, but not limited to, UTF (Unicode Transformation Format) 8; UTF16; etc.
In one particular example, a Load Count to Block Boundary (LCBB) instruction is provided that provides the number of bytes of data to a specified memory boundary from a specified address in memory. In computing the number of bytes (referred to herein as a count), a boundary size is used. The boundary size may be specified explicitly by the instruction (e.g., a variable value in the instruction text, a fixed instruction text value encoded in the opcode, a register based boundary specified in the instruction, etc.); or the boundary size may be dynamically determined by the machine. For instance, the instruction specifies the type of boundary, such as a page or cache boundary, and the machine determines the cache line or page size, either by a pre-specified value or dynamically based on the information (e.g., look-up in, for instance, a Translation Look-Aside Buffer to determine the page size).
As one example, the Load Count to Block Boundary instruction provides the number of bytes of data that can be or have been loaded from memory into, for instance, a register without crossing a specified boundary of the memory. The register can be a vector register or any other type of register.
A vector register (also referred to as a vector) includes one or more elements, and an element of a vector register (also referred to as a vector) is one, two or four bytes in length, as examples. Further, a vector operand is, for instance, a SIMD (Single Instruction, Multiple Data) operand having a plurality of elements. In other embodiments, elements can be of other sizes; and a vector operand need not be SIMD, and/or may include one element.
One embodiment of a computing environment to incorporate and use one or more aspects of the present invention is described with reference to FIG. 1. A computing environment 100 includes, for instance, a processor 102 (e.g., a central processing unit), a memory 104 (e.g., main memory), and one or more input/output (I/O) devices and/or interfaces 106 coupled to one another via, for example, one or more buses 108 and/or other connections.
In one example, processor 102 is based on the z/Architecture offered by International Business Machines Corporation, and is part of a server, such as the System z server, which is also offered by International Business Machines Corporation and implements the z/Architecture. One embodiment of the z/Architecture is described in an IBM® publication entitled, “z/Architecture Principles of Operation,” IBM® Publication No. SA22-7832-08, Ninth Edition, August, 2010, which is hereby incorporated herein by reference in its entirety. In one example, the processor executes an operating system, such as z/OS, also offered by International Business Machines Corporation. IBM®, Z/ARCHITECTURE® and Z/OS® are registered trademarks of International Business Machines Corporation, Armonk, N.Y., USA. Other names used herein may be registered trademarks, trademarks, or product names of International Business Machines Corporation or other companies.
In a further embodiment, processor 102 is based on the Power Architecture offered by International Business Machines Corporation. One embodiment of the Power Architecture is described in “Power ISATM Version 2.06 Revision B,” International Business Machines Corporation, Jul. 23, 2010, which is hereby incorporated herein by reference in its entirety. POWER ARCHITECTURE® is a registered trademark of International Business Machines Corporation.
In yet a further embodiment, processor 102 is based on an Intel architecture offered by Intel Corporation. One embodiment of the Intel architecture is described in “Intel® 64 and IA-32 Architectures Developer's Manual: Vol. 2B, Instructions Set Reference, A-L,” Order Number 253666-041US, December 2011, and “Intel® 64 and IA-32 Architectures Developer's Manual: Vol. 2B, Instructions Set Reference, M-Z,” Order Number 253667-041US, December 2011, each of which is hereby incorporated herein by reference in its entirety. Intel® is a registered trademark of Intel Corporation, Santa Clara, Calif.
Another embodiment of a computing environment to incorporate and use one or more aspects of the present invention is described with reference to FIG. 2A. In this example, a computing environment 200 includes, for instance, a native central processing unit 202, a memory 204, and one or more input/output devices and/or interfaces 206 coupled to one another via, for example, one or more buses 208 and/or other connections. As examples, computing environment 200 may include a PowerPC processor, a pSeries server or an xSeries server offered by International Business Machines Corporation, Armonk, N.Y.; an HP Superdome with Intel Itanium II processors offered by Hewlett Packard Co., Palo Alto, Calif.; and/or other machines based on architectures offered by International Business Machines Corporation, Hewlett Packard, Intel, Oracle, or others.
Native central processing unit 202 includes one or more native registers 210, such as one or more general purpose registers and/or one or more special purpose registers used during processing within the environment. These registers include information that represent the state of the environment at any particular point in time.
Moreover, native central processing unit 202 executes instructions and code that are stored in memory 204. In one particular example, the central processing unit executes emulator code 212 stored in memory 204. This code enables the processing environment configured in one architecture to emulate another architecture. For instance, emulator code 212 allows machines based on architectures other than the z/Architecture, such as PowerPC processors, pSeries servers, xSeries servers, HP Superdome servers or others, to emulate the z/Architecture and to execute software and instructions developed based on the z/Architecture.
Further details relating to emulator code 212 are described with reference to FIG. 2B. Guest instructions 250 comprise software instructions (e.g., machine instructions) that were developed to be executed in an architecture other than that of native CPU 202. For example, guest instructions 250 may have been designed to execute on a z/Architecture processor 102, but instead, are being emulated on native CPU 202, which may be, for example, an Intel Itanium II processor. In one example, emulator code 212 includes an instruction fetching unit 252 to obtain one or more guest instructions 250 from memory 204, and to optionally provide local buffering for the instructions obtained. It also includes an instruction translation routine 254 to determine the type of guest instruction that has been obtained and to translate the guest instruction into one or more corresponding native instructions 256. This translation includes, for instance, identifying the function to be performed by the guest instruction and choosing the native instruction(s) to perform that function.
Further, emulator 212 includes an emulation control routine 260 to cause the native instructions to be executed. Emulation control routine 260 may cause native CPU 202 to execute a routine of native instructions that emulate one or more previously obtained guest instructions and, at the conclusion of such execution, return control to the instruction fetch routine to emulate the obtaining of the next guest instruction or a group of guest instructions. Execution of the native instructions 256 may include loading data into a register from memory 204; storing data back to memory from a register; or performing some type of arithmetic or logic operation, as determined by the translation routine.
Each routine is, for instance, implemented in software, which is stored in memory and executed by native central processing unit 202. In other examples, one or more of the routines or operations are implemented in firmware, hardware, software or some combination thereof. The registers of the emulated processor may be emulated using registers 210 of the native CPU or by using locations in memory 204. In embodiments, guest instructions 250, native instructions 256 and emulator code 212 may reside in the same memory or may be disbursed among different memory devices.
As used herein, firmware includes, e.g., the microcode, millicode and/or macrocode of the processor. It includes, for instance, the hardware-level instructions and/or data structures used in implementation of higher level machine code. In one embodiment, it includes, for instance, proprietary code that is typically delivered as microcode that includes trusted software or microcode specific to the underlying hardware and controls operating system access to the system hardware.
In one example, a guest instruction 250 that is obtained, translated and executed is the instruction described herein. The instruction, which is of one architecture (e.g., the z/Architecture) is fetched from memory, translated and represented as a sequence of native instructions 256 of another architecture (e.g., PowerPC, pSeries, xSeries, Intel, etc.). These native instructions are then executed.
As described herein, the Load Count to Block Boundary instructions can be implemented as part of various architectures, including, but not limited to, the z/Architecture, Power, Intel, etc. Although an embodiment described herein is for the z/Architecture, the instruction and one or more aspects of the present invention may be based on many other architectures. The z/Architecture is only one example.
One embodiment of a Load Count to Block Boundary instruction is depicted in FIG. 3. In one example, the Load Count to Block Boundary instruction 300 includes opcode fields 302a (e.g., bits 0-7), 302b (e.g., bits 40-47) indicating a Load Count to Block Boundary operation; a register field 304 (e.g., bits 8-11) used to designate a general purpose register (R1); an index field (X2) 306 (e.g., bits 12-15); a base field (B2) 308 (e.g., bits 16-19); a displacement field (D2) 310 (e.g., bits 20-31); and a mask field (M3) 312 (e.g., bits 32-35). Each of the fields 304-312, in one example, is separate and independent from the opcode field(s). Further, in one embodiment, they are separate and independent from one another; however, in other embodiments, more than one field may be combined. Further information on the use of these fields is described below.
In one example, selected bits (e.g., the first two bits) of the opcode designated by opcode field 302a specify the length and format of the instruction. In this particular example, the length is three halfwords, and the format is a register-and-index-storage operation with an extended opcode field.
The subscript number associated with a field of the instruction denotes the operand to which the field applies. For instance, the subscript number 1 associated with R1 denotes the first operand, and so forth. The register operand is one register in length, which is, for instance, 128 bits.
In one example, in a register-and-index storage operation instruction, the contents of general registers designated by the X2 and B2 fields are added to the contents of the D2 field to form a second operand address. The displacement, D2, for the Load Count to Block Boundary instruction is treated as a 12 bit unsigned integer, in one example. The second operand address is used to indicate a location in main memory; however, it is not used to address data, in this embodiment.
The M3 field, in one embodiment, specifies a code that is used to signal the CPU as to the block boundary size to compute the number of possible bytes to load without crossing a memory boundary. If a reserved value is specified, a specification exception is recognized. Example codes and corresponding values are as follows:














Code
Boundary









0
64-Byte



1
128-Byte



2
256-Byte



3
512-Byte



4
1K-Byte



5
2K-Byte



6
4K-Byte










In a further example, the boundary size is not included in the instruction, but instead, is dynamically determined by the processor executing the instruction. For instance, the M3 field specifies the type of boundary (e.g., cache line, page, etc.), and based on the type and one or more characteristics of the processor (e.g., cache line size for the processor; page size for the processor; etc.), the processor determines the boundary. As examples, based on the type, the processor uses a fixed size for the boundary (e.g., pre-defined fixed cache line or page size for the processor), or based on the type, the processor determines the boundary. For instance, if the type is a page boundary, the processor looks up the start address in a Translation Look-Aside Buffer (TLB) and determines the page boundary therefrom. Other examples also exist. For example, the type may be provided by another field of the instruction or from a control outside of the instruction.
In execution of one embodiment of the Load Count to Block Boundary instruction, an unsigned binary integer (e.g., 64-bits) containing the number of bytes possible to load from the second operand location without crossing a specified block boundary, capped at, for instance, the size of a vector to be loaded (e.g., 16), is placed in the general purpose register specified in the first operand.
Resulting from execution of the instruction, an optional condition code is set, such as, for example:
0—Operand one is sixteen
1—
2—
3—Operand one is less than sixteen
In the example instruction above, the second operand address is determined by the index register value (X2)+a base register value (B2)+a displacement (D2); however, in other embodiments, it is provided by a register value; an instruction address+instruction text specified offset; a register value+displacement; or a register value+index register value; as just some examples.
Further details of one embodiment of processing the Load Count to Block Boundary instruction are described with reference to FIG. 4. In one example, a processor of the computing environment is performing this logic.
In one embodiment, initially a boundary mask (BdyMask) is created, which is used to determine closeness to the specified boundary, STEP 400. To create the mask, in one example, a 2's complement negation of a boundary size (BdySize) 402 is taken creating boundary mask 404 (e.g., BdyMask=0−BdySize). The boundary size is provided, in one example, by the instruction (e.g., the M3 field); or in another example, it is determined by the machine, as described herein.
Thereafter, a start address is computed, which indicates a location in memory from which the count is to begin, STEP 410. As examples, the start address 412 can be provided by a register value; an instruction address plus instruction text specified offset; a register value plus displacement; a register value plus index register value; or a register value plus index register value plus displacement. In the instruction provided herein, the start address is provided by the X2 field, B2 field and D2 field. That is, contents of the registers designated by X2 and B2 are added to the displacement indicated by D2 to provide the starting address. The above-indicated ways to compute a starting address are just examples; other examples are also possible.
Next, an end address is computed indicating a location at which counting is to stop, STEP 420. Input to this computation is, for instance, boundary size 402, start address 412, vector size (vec_size) 414, and boundary mask 404. The vector size is the size of a selected vector register or other register (e.g., in bytes; e.g., 16). The register is, for instance, a register in which data may be loaded. In one example, end address 422 is computed as follows:

EndAddress=min(StartAddress+(BdySize−(StartAddress & BdyMask)), StartAddress+vec_size).

Thereafter, the count is computed, STEP 430. For instance, count=EndAddress 422−StartAddress 412. In a further example, the count can be computed from the start address and without using the end address. In this example, count=min(16, BdySize−(StartAddress AND BdyMask)), where 16 is the size of the vector register (or other register) in bytes. In other examples, other vector sizes may be used.
One example of at least a portion of a memory block 500 is depicted in FIG. 5A. Memory block 500 includes data from a selected address 502 to a specified boundary 504. As indicated, no data is counted or loaded past the boundary designated by the dashed vertical line 504. The locations past the boundary are not accessible and no exception is taken. Further, a count of the distance from the selected address to the specified boundary, determined in accordance with an aspect of the present invention, is stored in a general purpose register 510, an example of which is depicted in FIG. 5B. As shown, in this example, the count is 13 hex, and therefore 0D is stored in general purpose register 510 indicating 13 bytes of data have been counted and may be stored in a vector register.
Described above is one example of a count instruction used to determine the distance from a specified address to a specified boundary. An alert may be provided if the specified address is near the boundary, thus, possibly requiring special handling.
As one example, the Load Count to Block Boundary instruction is used to determine how many bytes of data were loaded into a register, such as a vector register. This count may then be used in other processing.
In one embodiment, the register that is loaded and for which a count is obtained is a vector register, which is part of a vector facility. The vector facility provides, for instance, fixed sized vectors ranging from one to sixteen elements. Each vector includes data which is operated on by vector instructions defined in the facility. In one embodiment, if a vector is made up of multiple elements, then each element is processed in parallel with the other elements. Instruction completion does not occur until processing of all the elements is complete.
As one example, there are 32 vector registers and other types of registers can map to a quadrant of the vector registers. For instance, as shown in FIG. 6, if there is a register file 600 that includes 32 vector registers 602 and each register is 128 bits in length, then 16 floating point registers 604, which are 64 bits in length, can overlay the vector registers. Thus, as an example, when floating point register 2 is modified, then vector register 2 is also modified. Other mappings for other types of registers is also possible.
Herein, memory, main memory, storage and main storage are used interchangeably, unless otherwise noted explicitly or by context.
Additional details relating to the vector facility, including examples of other instructions, are provided as part of this Detailed Description further below.
As will be appreciated by one skilled in the art, one or more aspects of the present invention may be embodied as a system, method or computer program product. Accordingly, one or more aspects of the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment (including firmware, resident software, micro-code, etc.) or an embodiment combining software and hardware aspects that may all generally be referred to herein as a “circuit,” “module” or “system”. Furthermore, one or more aspects of the present invention may take the form of a computer program product embodied in one or more computer readable medium(s) having computer readable program code embodied thereon.
Any combination of one or more computer readable medium(s) may be utilized. The computer readable medium may be a computer readable storage medium. A computer readable storage medium may be, for example, but not limited to, an electronic, magnetic, optical, electromagnetic, infrared or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples (a non-exhaustive list) of the computer readable storage medium include the following: an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing. In the context of this document, a computer readable storage medium may be any tangible medium that can contain or store a program for use by or in connection with an instruction execution system, apparatus, or device.
Referring now to FIG. 7, in one example, a computer program product 700 includes, for instance, one or more non-transitory computer readable storage media 702 to store computer readable program code means or logic 704 thereon to provide and facilitate one or more aspects of the present invention.
Program code embodied on a computer readable medium may be transmitted using an appropriate medium, including but not limited to wireless, wireline, optical fiber cable, RF, etc., or any suitable combination of the foregoing.
Computer program code for carrying out operations for one or more aspects of the present invention may be written in any combination of one or more programming languages, including an object oriented programming language, such as Java, Smalltalk, C++ or the like, and conventional procedural programming languages, such as the “C” programming language, assembler or similar programming languages. The program code may execute entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer or entirely on the remote computer or server. In the latter scenario, the remote computer may be connected to the user's computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or the connection may be made to an external computer (for example, through the Internet using an Internet Service Provider).
One or more aspects of the present invention are described herein with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and/or block diagrams, and combinations of blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer readable medium that can direct a computer, other programmable data processing apparatus, or other devices to function in a particular manner, such that the instructions stored in the computer readable medium produce an article of manufacture including instructions which implement the function/act specified in the flowchart and/or block diagram block or blocks.
The computer program instructions may also be loaded onto a computer, other programmable data processing apparatus, or other devices to cause a series of operational steps to be performed on the computer, other programmable apparatus or other devices to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide processes for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks.
The flowchart and block diagrams in the figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods and computer program products according to various embodiments of one or more aspects of the present invention. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of code, which comprises one or more executable instructions for implementing the specified logical function(s). It should also be noted that, in some alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and/or flowchart illustration, and combinations of blocks in the block diagrams and/or flowchart illustration, can be implemented by special purpose hardware-based systems that perform the specified functions or acts, or combinations of special purpose hardware and computer instructions.
In addition to the above, one or more aspects of the present invention may be provided, offered, deployed, managed, serviced, etc. by a service provider who offers management of customer environments. For instance, the service provider can create, maintain, support, etc. computer code and/or a computer infrastructure that performs one or more aspects of the present invention for one or more customers. In return, the service provider may receive payment from the customer under a subscription and/or fee agreement, as examples. Additionally or alternatively, the service provider may receive payment from the sale of advertising content to one or more third parties.
In one aspect of the present invention, an application may be deployed for performing one or more aspects of the present invention. As one example, the deploying of an application comprises providing computer infrastructure operable to perform one or more aspects of the present invention.
As a further aspect of the present invention, a computing infrastructure may be deployed comprising integrating computer readable code into a computing system, in which the code in combination with the computing system is capable of performing one or more aspects of the present invention.
As yet a further aspect of the present invention, a process for integrating computing infrastructure comprising integrating computer readable code into a computer system may be provided. The computer system comprises a computer readable medium, in which the computer medium comprises one or more aspects of the present invention. The code in combination with the computer system is capable of performing one or more aspects of the present invention.
Although various embodiments are described above, these are only examples. For example, computing environments of other architectures can incorporate and use one or more aspects of the present invention. Further, vectors of other sizes and other registers may be used, and changes to the instruction may be made without departing from the spirit of the present invention. Further, other techniques may be used to compute the distance from a specified address to a particular boundary.
Further, other types of computing environments can benefit from one or more aspects of the present invention. As an example, a data processing system suitable for storing and/or executing program code is usable that includes at least two processors coupled directly or indirectly to memory elements through a system bus. The memory elements include, for instance, local memory employed during actual execution of the program code, bulk storage, and cache memory which provide temporary storage of at least some program code in order to reduce the number of times code must be retrieved from bulk storage during execution.
Input/Output or I/O devices (including, but not limited to, keyboards, displays, pointing devices, DASD, tape, CDs, DVDs, thumb drives and other memory media, etc.) can be coupled to the system either directly or through intervening I/O controllers. Network adapters may also be coupled to the system to enable the data processing system to become coupled to other data processing systems or remote printers or storage devices through intervening private or public networks. Modems, cable modems, and Ethernet cards are just a few of the available types of network adapters.
Referring to FIG. 8, representative components of a Host Computer system 5000 to implement one or more aspects of the present invention are portrayed. The representative host computer 5000 comprises one or more CPUs 5001 in communication with computer memory (i.e., central storage) 5002, as well as I/O interfaces to storage media devices 5011 and networks 5010 for communicating with other computers or SANs and the like. The CPU 5001 is compliant with an architecture having an architected instruction set and architected functionality. The CPU 5001 may have dynamic address translation (DAT) 5003 for transforming program addresses (virtual addresses) into real addresses of memory. A DAT typically includes a translation lookaside buffer (TLB) 5007 for caching translations so that later accesses to the block of computer memory 5002 do not require the delay of address translation. Typically, a cache 5009 is employed between computer memory 5002 and the processor 5001. The cache 5009 may be hierarchical having a large cache available to more than one CPU and smaller, faster (lower level) caches between the large cache and each CPU. In some implementations, the lower level caches are split to provide separate low level caches for instruction fetching and data accesses. In one embodiment, an instruction is fetched from memory 5002 by an instruction fetch unit 5004 via a cache 5009. The instruction is decoded in an instruction decode unit 5006 and dispatched (with other instructions in some embodiments) to instruction execution unit or units 5008. Typically several execution units 5008 are employed, for example an arithmetic execution unit, a floating point execution unit and a branch instruction execution unit. The instruction is executed by the execution unit, accessing operands from instruction specified registers or memory as needed. If an operand is to be accessed (loaded or stored) from memory 5002, a load/store unit 5005 typically handles the access under control of the instruction being executed. Instructions may be executed in hardware circuits or in internal microcode (firmware) or by a combination of both.
As noted, a computer system includes information in local (or main) storage, as well as addressing, protection, and reference and change recording. Some aspects of addressing include the format of addresses, the concept of address spaces, the various types of addresses, and the manner in which one type of address is translated to another type of address. Some of main storage includes permanently assigned storage locations. Main storage provides the system with directly addressable fast-access storage of data. Both data and programs are to be loaded into main storage (from input devices) before they can be processed.
Main storage may include one or more smaller, faster-access buffer storages, sometimes called caches. A cache is typically physically associated with a CPU or an I/O processor. The effects, except on performance, of the physical construction and use of distinct storage media are generally not observable by the program.
Separate caches may be maintained for instructions and for data operands. Information within a cache is maintained in contiguous bytes on an integral boundary called a cache block or cache line (or line, for short). A model may provide an EXTRACT CACHE ATTRIBUTE instruction which returns the size of a cache line in bytes. A model may also provide PREFETCH DATA and PREFETCH DATA RELATIVE LONG instructions which effects the prefetching of storage into the data or instruction cache or the releasing of data from the cache.
Storage is viewed as a long horizontal string of bits. For most operations, accesses to storage proceed in a left-to-right sequence. The string of bits is subdivided into units of eight bits. An eight-bit unit is called a byte, which is the basic building block of all information formats. Each byte location in storage is identified by a unique nonnegative integer, which is the address of that byte location or, simply, the byte address. Adjacent byte locations have consecutive addresses, starting with 0 on the left and proceeding in a left-to-right sequence. Addresses are unsigned binary integers and are 24, 31, or 64 bits.
Information is transmitted between storage and a CPU or a channel subsystem one byte, or a group of bytes, at a time. Unless otherwise specified, in, for instance, the z/Architecture, a group of bytes in storage is addressed by the leftmost byte of the group. The number of bytes in the group is either implied or explicitly specified by the operation to be performed. When used in a CPU operation, a group of bytes is called a field. Within each group of bytes, in, for instance, the z/Architecture, bits are numbered in a left-to-right sequence. In the z/Architecture, the leftmost bits are sometimes referred to as the “high-order” bits and the rightmost bits as the “low-order” bits. Bit numbers are not storage addresses, however. Only bytes can be addressed. To operate on individual bits of a byte in storage, the entire byte is accessed. The bits in a byte are numbered 0 through 7, from left to right (in, e.g., the z/Architecture). The bits in an address may be numbered 8-31 or 40-63 for 24-bit addresses, or 1-31 or 33-63 for 31-bit addresses; they are numbered 0-63 for 64-bit addresses. Within any other fixed-length format of multiple bytes, the bits making up the format are consecutively numbered starting from 0. For purposes of error detection, and in preferably for correction, one or more check bits may be transmitted with each byte or with a group of bytes. Such check bits are generated automatically by the machine and cannot be directly controlled by the program. Storage capacities are expressed in number of bytes. When the length of a storage-operand field is implied by the operation code of an instruction, the field is said to have a fixed length, which can be one, two, four, eight, or sixteen bytes. Larger fields may be implied for some instructions. When the length of a storage-operand field is not implied but is stated explicitly, the field is said to have a variable length. Variable-length operands can vary in length by increments of one byte (or with some instructions, in multiples of two bytes or other multiples). When information is placed in storage, the contents of only those byte locations are replaced that are included in the designated field, even though the width of the physical path to storage may be greater than the length of the field being stored.
Certain units of information are to be on an integral boundary in storage. A boundary is called integral for a unit of information when its storage address is a multiple of the length of the unit in bytes. Special names are given to fields of 2, 4, 8, and 16 bytes on an integral boundary. A halfword is a group of two consecutive bytes on a two-byte boundary and is the basic building block of instructions. A word is a group of four consecutive bytes on a four-byte boundary. A doubleword is a group of eight consecutive bytes on an eight-byte boundary. A quadword is a group of 16 consecutive bytes on a 16-byte boundary. When storage addresses designate halfwords, words, doublewords, and quadwords, the binary representation of the address contains one, two, three, or four rightmost zero bits, respectively. Instructions are to be on two-byte integral boundaries. The storage operands of most instructions do not have boundary-alignment requirements.
On devices that implement separate caches for instructions and data operands, a significant delay may be experienced if the program stores into a cache line from which instructions are subsequently fetched, regardless of whether the store alters the instructions that are subsequently fetched.
In one embodiment, the invention may be practiced by software (sometimes referred to licensed internal code, firmware, micro-code, milli-code, pico-code and the like, any of which would be consistent with one or more aspects the present invention). Referring to FIG. 8, software program code which embodies one or more aspects of the present invention may be accessed by processor 5001 of the host system 5000 from long-term storage media devices 5011, such as a CD-ROM drive, tape drive or hard drive. The software program code may be embodied on any of a variety of known media for use with a data processing system, such as a diskette, hard drive, or CD-ROM. The code may be distributed on such media, or may be distributed to users from computer memory 5002 or storage of one computer system over a network 5010 to other computer systems for use by users of such other systems.
The software program code includes an operating system which controls the function and interaction of the various computer components and one or more application programs. Program code is normally paged from storage media device 5011 to the relatively higher-speed computer storage 5002 where it is available for processing by processor 5001. The techniques and methods for embodying software program code in memory, on physical media, and/or distributing software code via networks are well known and will not be further discussed herein. Program code, when created and stored on a tangible medium (including but not limited to electronic memory modules (RAM), flash memory, Compact Discs (CDs), DVDs, Magnetic Tape and the like is often referred to as a “computer program product”. The computer program product medium is typically readable by a processing circuit preferably in a computer system for execution by the processing circuit.
FIG. 9 illustrates a representative workstation or server hardware system in which one or more aspects of the present invention may be practiced. The system 5020 of FIG. 9 comprises a representative base computer system 5021, such as a personal computer, a workstation or a server, including optional peripheral devices. The base computer system 5021 includes one or more processors 5026 and a bus employed to connect and enable communication between the processor(s) 5026 and the other components of the system 5021 in accordance with known techniques. The bus connects the processor 5026 to memory 5025 and long-term storage 5027 which can include a hard drive (including any of magnetic media, CD, DVD and Flash Memory for example) or a tape drive for example. The system 5021 might also include a user interface adapter, which connects the microprocessor 5026 via the bus to one or more interface devices, such as a keyboard 5024, a mouse 5023, a printer/scanner 5030 and/or other interface devices, which can be any user interface device, such as a touch sensitive screen, digitized entry pad, etc. The bus also connects a display device 5022, such as an LCD screen or monitor, to the microprocessor 5026 via a display adapter.
The system 5021 may communicate with other computers or networks of computers by way of a network adapter capable of communicating 5028 with a network 5029. Example network adapters are communications channels, token ring, Ethernet or modems. Alternatively, the system 5021 may communicate using a wireless interface, such as a CDPD (cellular digital packet data) card. The system 5021 may be associated with such other computers in a Local Area Network (LAN) or a Wide Area Network (WAN), or the system 5021 can be a client in a client/server arrangement with another computer, etc. All of these configurations, as well as the appropriate communications hardware and software, are known in the art.
FIG. 10 illustrates a data processing network 5040 in which one or more aspects of the present invention may be practiced. The data processing network 5040 may include a plurality of individual networks, such as a wireless network and a wired network, each of which may include a plurality of individual workstations 5041, 5042, 5043, 5044. Additionally, as those skilled in the art will appreciate, one or more LANs may be included, where a LAN may comprise a plurality of intelligent workstations coupled to a host processor.
Still referring to FIG. 10, the networks may also include mainframe computers or servers, such as a gateway computer (client server 5046) or application server (remote server 5048 which may access a data repository and may also be accessed directly from a workstation 5045). A gateway computer 5046 serves as a point of entry into each individual network. A gateway is needed when connecting one networking protocol to another. The gateway 5046 may be preferably coupled to another network (the Internet 5047 for example) by means of a communications link. The gateway 5046 may also be directly coupled to one or more workstations 5041, 5042, 5043, 5044 using a communications link. The gateway computer may be implemented utilizing an IBM eServerTM System z server available from International Business Machines Corporation.
Referring concurrently to FIG. 9 and FIG. 10, software programming code which may embody one or more aspects of the present invention may be accessed by the processor 5026 of the system 5020 from long-term storage media 5027, such as a CD-ROM drive or hard drive. The software programming code may be embodied on any of a variety of known media for use with a data processing system, such as a diskette, hard drive, or CD-ROM. The code may be distributed on such media, or may be distributed to users 5050, 5051 from the memory or storage of one computer system over a network to other computer systems for use by users of such other systems.
Alternatively, the programming code may be embodied in the memory 5025, and accessed by the processor 5026 using the processor bus. Such programming code includes an operating system which controls the function and interaction of the various computer components and one or more application programs 5032. Program code is normally paged from storage media 5027 to high-speed memory 5025 where it is available for processing by the processor 5026. The techniques and methods for embodying software programming code in memory, on physical media, and/or distributing software code via networks are well known and will not be further discussed herein. Program code, when created and stored on a tangible medium (including but not limited to electronic memory modules (RAM), flash memory, Compact Discs (CDs), DVDs, Magnetic Tape and the like is often referred to as a “computer program product”. The computer program product medium is typically readable by a processing circuit preferably in a computer system for execution by the processing circuit.
The cache that is most readily available to the processor (normally faster and smaller than other caches of the processor) is the lowest (L1 or level one) cache and main store (main memory) is the highest level cache (L3 if there are 3 levels). The lowest level cache is often divided into an instruction cache (I-Cache) holding machine instructions to be executed and a data cache (D-Cache) holding data operands.
Referring to FIG. 11, an exemplary processor embodiment is depicted for processor 5026. Typically one or more levels of cache 5053 are employed to buffer memory blocks in order to improve processor performance. The cache 5053 is a high speed buffer holding cache lines of memory data that are likely to be used. Typical cache lines are 64, 128 or 256 bytes of memory data. Separate caches are often employed for caching instructions than for caching data. Cache coherence (synchronization of copies of lines in memory and the caches) is often provided by various “snoop” algorithms well known in the art. Main memory storage 5025 of a processor system is often referred to as a cache. In a processor system having 4 levels of cache 5053, main storage 5025 is sometimes referred to as the level 5 (L5) cache since it is typically faster and only holds a portion of the non-volatile storage (DASD, tape etc) that is available to a computer system. Main storage 5025 “caches” pages of data paged in and out of the main storage 5025 by the operating system.
A program counter (instruction counter) 5061 keeps track of the address of the current instruction to be executed. A program counter in a z/Architecture processor is 64 bits and can be truncated to 31 or 24 bits to support prior addressing limits. A program counter is typically embodied in a PSW (program status word) of a computer such that it persists during context switching. Thus, a program in progress, having a program counter value, may be interrupted by, for example, the operating system (context switch from the program environment to the operating system environment). The PSW of the program maintains the program counter value while the program is not active, and the program counter (in the PSW) of the operating system is used while the operating system is executing. Typically, the program counter is incremented by an amount equal to the number of bytes of the current instruction. RISC (Reduced Instruction Set Computing) instructions are typically fixed length while CISC (Complex Instruction Set Computing) instructions are typically variable length. Instructions of the IBM z/Architecture are CISC instructions having a length of 2, 4 or 6 bytes. The Program counter 5061 is modified by either a context switch operation or a branch taken operation of a branch instruction for example. In a context switch operation, the current program counter value is saved in the program status word along with other state information about the program being executed (such as condition codes), and a new program counter value is loaded pointing to an instruction of a new program module to be executed. A branch taken operation is performed in order to permit the program to make decisions or loop within the program by loading the result of the branch instruction into the program counter 5061.
Typically an instruction fetch unit 5055 is employed to fetch instructions on behalf of the processor 5026. The fetch unit either fetches “next sequential instructions”, target instructions of branch taken instructions, or first instructions of a program following a context switch. Modern Instruction fetch units often employ prefetch techniques to speculatively prefetch instructions based on the likelihood that the prefetched instructions might be used. For example, a fetch unit may fetch 16 bytes of instruction that includes the next sequential instruction and additional bytes of further sequential instructions.
The fetched instructions are then executed by the processor 5026. In an embodiment, the fetched instruction(s) are passed to a dispatch unit 5056 of the fetch unit. The dispatch unit decodes the instruction(s) and forwards information about the decoded instruction(s) to appropriate units 5057, 5058, 5060. An execution unit 5057 will typically receive information about decoded arithmetic instructions from the instruction fetch unit 5055 and will perform arithmetic operations on operands according to the opcode of the instruction. Operands are provided to the execution unit 5057 preferably either from memory 5025, architected registers 5059 or from an immediate field of the instruction being executed. Results of the execution, when stored, are stored either in memory 5025, registers 5059 or in other machine hardware (such as control registers, PSW registers and the like).
A processor 5026 typically has one or more units 5057, 5058, 5060 for executing the function of the instruction. Referring to FIG. 12A, an execution unit 5057 may communicate with architected general registers 5059, a decode/dispatch unit 5056, a load store unit 5060, and other 5065 processor units by way of interfacing logic 5071. An execution unit 5057 may employ several register circuits 5067, 5068, 5069 to hold information that the arithmetic logic unit (ALU) 5066 will operate on. The ALU performs arithmetic operations such as add, subtract, multiply and divide as well as logical function such as and, or and exclusive- or (XOR), rotate and shift. Preferably the ALU supports specialized operations that are design dependent. Other circuits may provide other architected facilities 5072 including condition codes and recovery support logic for example. Typically the result of an ALU operation is held in an output register circuit 5070 which can forward the result to a variety of other processing functions. There are many arrangements of processor units, the present description is only intended to provide a representative understanding of one embodiment.
An ADD instruction for example would be executed in an execution unit 5057 having arithmetic and logical functionality while a floating point instruction for example would be executed in a floating point execution having specialized floating point capability. Preferably, an execution unit operates on operands identified by an instruction by performing an opcode defined function on the operands. For example, an ADD instruction may be executed by an execution unit 5057 on operands found in two registers 5059 identified by register fields of the instruction.
The execution unit 5057 performs the arithmetic addition on two operands and stores the result in a third operand where the third operand may be a third register or one of the two source registers. The execution unit preferably utilizes an Arithmetic Logic Unit (ALU) 5066 that is capable of performing a variety of logical functions such as Shift, Rotate, And, Or and XOR as well as a variety of algebraic functions including any of add, subtract, multiply, divide. Some ALUs 5066 are designed for scalar operations and some for floating point. Data may be Big Endian (where the least significant byte is at the highest byte address) or Little Endian (where the least significant byte is at the lowest byte address) depending on architecture. The IBM z/Architecture is Big Endian. Signed fields may be sign and magnitude, 1's complement or 2's complement depending on architecture. A 2's complement number is advantageous in that the ALU does not need to design a subtract capability since either a negative value or a positive value in 2's complement requires only an addition within the ALU. Numbers are commonly described in shorthand, where a 12 bit field defines an address of a 4,096 byte block and is commonly described as a 4 Kbyte (Kilo-byte) block, for example.
Referring to FIG. 12B, branch instruction information for executing a branch instruction is typically sent to a branch unit 5058 which often employs a branch prediction algorithm such as a branch history table 5082 to predict the outcome of the branch before other conditional operations are complete. The target of the current branch instruction will be fetched and speculatively executed before the conditional operations are complete. When the conditional operations are completed the speculatively executed branch instructions are either completed or discarded based on the conditions of the conditional operation and the speculated outcome. A typical branch instruction may test condition codes and branch to a target address if the condition codes meet the branch requirement of the branch instruction, a target address may be calculated based on several numbers including ones found in register fields or an immediate field of the instruction for example. The branch unit 5058 may employ an ALU 5074 having a plurality of input register circuits 5075, 5076, 5077 and an output register circuit 5080. The branch unit 5058 may communicate with general registers 5059, decode dispatch unit 5056 or other circuits 5073, for example.
The execution of a group of instructions can be interrupted for a variety of reasons including a context switch initiated by an operating system, a program exception or error causing a context switch, an I/O interruption signal causing a context switch or multi-threading activity of a plurality of programs (in a multi-threaded environment), for example. Preferably a context switch action saves state information about a currently executing program and then loads state information about another program being invoked. State information may be saved in hardware registers or in memory for example. State information preferably comprises a program counter value pointing to a next instruction to be executed, condition codes, memory translation information and architected register content. A context switch activity can be exercised by hardware circuits, application programs, operating system programs or firmware code (microcode, pico-code or licensed internal code (LIC)) alone or in combination.
A processor accesses operands according to instruction defined methods. The instruction may provide an immediate operand using the value of a portion of the instruction, may provide one or more register fields explicitly pointing to either general purpose registers or special purpose registers (floating point registers for example). The instruction may utilize implied registers identified by an opcode field as operands. The instruction may utilize memory locations for operands. A memory location of an operand may be provided by a register, an immediate field, or a combination of registers and immediate field as exemplified by the z/Architecture long displacement facility wherein the instruction defines a base register, an index register and an immediate field (displacement field) that are added together to provide the address of the operand in memory for example. Location herein typically implies a location in main memory (main storage) unless otherwise indicated.
Referring to FIG. 12C, a processor accesses storage using a load/store unit 5060. The load/store unit 5060 may perform a load operation by obtaining the address of the target operand in memory 5053 and loading the operand in a register 5059 or another memory 5053 location, or may perform a store operation by obtaining the address of the target operand in memory 5053 and storing data obtained from a register 5059 or another memory 5053 location in the target operand location in memory 5053. The load/store unit 5060 may be speculative and may access memory in a sequence that is out-of-order relative to instruction sequence, however the load/store unit 5060 is to maintain the appearance to programs that instructions were executed in order. A load/store unit 5060 may communicate with general registers 5059, decode/dispatch unit 5056, cache/memory interface 5053 or other elements 5083 and comprises various register circuits, ALUs 5085 and control logic 5090 to calculate storage addresses and to provide pipeline sequencing to keep operations in-order. Some operations may be out of order but the load/store unit provides functionality to make the out of order operations to appear to the program as having been performed in order, as is well known in the art.
Preferably addresses that an application program “sees” are often referred to as virtual addresses. Virtual addresses are sometimes referred to as “logical addresses” and “effective addresses”. These virtual addresses are virtual in that they are redirected to physical memory location by one of a variety of dynamic address translation (DAT) technologies including, but not limited to, simply prefixing a virtual address with an offset value, translating the virtual address via one or more translation tables, the translation tables preferably comprising at least a segment table and a page table alone or in combination, preferably, the segment table having an entry pointing to the page table. In the z/Architecture, a hierarchy of translation is provided including a region first table, a region second table, a region third table, a segment table and an optional page table. The performance of the address translation is often improved by utilizing a translation lookaside buffer (TLB) which comprises entries mapping a virtual address to an associated physical memory location. The entries are created when the DAT translates a virtual address using the translation tables. Subsequent use of the virtual address can then utilize the entry of the fast TLB rather than the slow sequential translation table accesses. TLB content may be managed by a variety of replacement algorithms including LRU (Least Recently used).
In the case where the processor is a processor of a multi-processor system, each processor has responsibility to keep shared resources, such as I/O, caches, TLBs and memory, interlocked for coherency. Typically, “snoop” technologies will be utilized in maintaining cache coherency. In a snoop environment, each cache line may be marked as being in any one of a shared state, an exclusive state, a changed state, an invalid state and the like in order to facilitate sharing.
I/O units 5054 (FIG. 11) provide the processor with means for attaching to peripheral devices including tape, disc, printers, displays, and networks for example. I/O units are often presented to the computer program by software drivers. In mainframes, such as the System Z® from IBM®, channel adapters and open system adapters are I/O units of the mainframe that provide the communications between the operating system and peripheral devices.
Further, other types of computing environments can benefit from one or more aspects of the present invention. As an example, an environment may include an emulator (e.g., software or other emulation mechanisms), in which a particular architecture (including, for instance, instruction execution, architected functions, such as address translation, and architected registers) or a subset thereof is emulated (e.g., on a native computer system having a processor and memory). In such an environment, one or more emulation functions of the emulator can implement one or more aspects of the present invention, even though a computer executing the emulator may have a different architecture than the capabilities being emulated. As one example, in emulation mode, the specific instruction or operation being emulated is decoded, and an appropriate emulation function is built to implement the individual instruction or operation.
In an emulation environment, a host computer includes, for instance, a memory to store instructions and data; an instruction fetch unit to fetch instructions from memory and to optionally, provide local buffering for the fetched instruction; an instruction decode unit to receive the fetched instructions and to determine the type of instructions that have been fetched; and an instruction execution unit to execute the instructions. Execution may include loading data into a register from memory; storing data back to memory from a register; or performing some type of arithmetic or logical operation, as determined by the decode unit. In one example, each unit is implemented in software. For instance, the operations being performed by the units are implemented as one or more subroutines within emulator software.
More particularly, in a mainframe, architected machine instructions are used by programmers, usually today “C” programmers, often by way of a compiler application. These instructions stored in the storage medium may be executed natively in a z/Architecture IBM® Server, or alternatively in machines executing other architectures. They can be emulated in the existing and in future IBM® mainframe servers and on other machines of IBM® (e.g., Power Systems servers and System X® Servers). They can be executed in machines running Linux on a wide variety of machines using hardware manufactured by IBM®, Intel®, AMDTM, and others. Besides execution on that hardware under a z/Architecture, Linux can be used as well as machines which use emulation by Hercules, UMX, or FSI (Fundamental Software, Inc), where generally execution is in an emulation mode. In emulation mode, emulation software is executed by a native processor to emulate the architecture of an emulated processor.
The native processor typically executes emulation software comprising either firmware or a native operating system to perform emulation of the emulated processor. The emulation software is responsible for fetching and executing instructions of the emulated processor architecture. The emulation software maintains an emulated program counter to keep track of instruction boundaries. The emulation software may fetch one or more emulated machine instructions at a time and convert the one or more emulated machine instructions to a corresponding group of native machine instructions for execution by the native processor. These converted instructions may be cached such that a faster conversion can be accomplished. Notwithstanding, the emulation software is to maintain the architecture rules of the emulated processor architecture so as to assure operating systems and applications written for the emulated processor operate correctly. Furthermore, the emulation software is to provide resources identified by the emulated processor architecture including, but not limited to, control registers, general purpose registers, floating point registers, dynamic address translation function including segment tables and page tables for example, interrupt mechanisms, context switch mechanisms, Time of Day (TOD) clocks and architected interfaces to I/O subsystems such that an operating system or an application program designed to run on the emulated processor, can be run on the native processor having the emulation software.
A specific instruction being emulated is decoded, and a subroutine is called to perform the function of the individual instruction. An emulation software function emulating a function of an emulated processor is implemented, for example, in a “C” subroutine or driver, or some other method of providing a driver for the specific hardware as will be within the skill of those in the art after understanding the description of the preferred embodiment. Various software and hardware emulation patents including, but not limited to U.S. Pat. No. 5,551,013, entitled “Multiprocessor for Hardware Emulation”, by Beausoleil et al.; and U.S. Pat. No. 6,009,261, entitled “Preprocessing of Stored Target Routines for Emulating Incompatible Instructions on a Target Processor”, by Scalzi et al; and U.S. Pat. No. 5,574,873, entitled “Decoding Guest Instruction to Directly Access Emulation Routines that Emulate the Guest Instructions”, by Davidian et al; and U.S. Pat. No. 6,308,255, entitled “Symmetrical Multiprocessing Bus and Chipset Used for Coprocessor Support Allowing Non-Native Code to Run in a System”, by Gorishek et al; and U.S. Pat. No. 6,463,582, entitled “Dynamic Optimizing Object Code Translator for Architecture Emulation and Dynamic Optimizing Object Code Translation Method”, by Lethin et al; and U.S. Pat. No. 5,790,825, entitled “Method for Emulating Guest Instructions on a Host Computer Through Dynamic Recompilation of Host Instructions”, by Eric Traut, each of which is hereby incorporated herein by reference in its entirety; and many others, illustrate a variety of known ways to achieve emulation of an instruction format architected for a different machine for a target machine available to those skilled in the art.
In FIG. 13, an example of an emulated host computer system 5092 is provided that emulates a host computer system 5000′ of a host architecture. In the emulated host computer system 5092, the host processor (CPU) 5091 is an emulated host processor (or virtual host processor) and comprises an emulation processor 5093 having a different native instruction set architecture than that of the processor 5091 of the host computer 5000′. The emulated host computer system 5092 has memory 5094 accessible to the emulation processor 5093. In the example embodiment, the memory 5094 is partitioned into a host computer memory 5096 portion and an emulation routines 5097 portion. The host computer memory 5096 is available to programs of the emulated host computer 5092 according to host computer architecture. The emulation processor 5093 executes native instructions of an architected instruction set of an architecture other than that of the emulated processor 5091, the native instructions obtained from emulation routines memory 5097, and may access a host instruction for execution from a program in host computer memory 5096 by employing one or more instruction(s) obtained in a sequence & access/decode routine which may decode the host instruction(s) accessed to determine a native instruction execution routine for emulating the function of the host instruction accessed. Other facilities that are defined for the host computer system 5000′ architecture may be emulated by architected facilities routines, including such facilities as general purpose registers, control registers, dynamic address translation and I/O subsystem support and processor cache, for example. The emulation routines may also take advantage of functions available in the emulation processor 5093 (such as general registers and dynamic translation of virtual addresses) to improve performance of the emulation routines. Special hardware and off-load engines may also be provided to assist the processor 5093 in emulating the function of the host computer 5000′.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising”, when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and/or groups thereof.
The corresponding structures, materials, acts, and equivalents of all means or step plus function elements in the claims below, if any, are intended to include any structure, material, or act for performing the function in combination with other claimed elements as specifically claimed. The description of one or more aspects of the present invention has been presented for purposes of illustration and description, but is not intended to be exhaustive or limited to the invention in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the invention. The embodiment was chosen and described in order to best explain the principles of the invention and the practical application, and to enable others of ordinary skill in the art to understand the invention for various embodiments with various modifications as are suited to the particular use contemplated.
Chapter 23. Vector String Instructions
Vector String Facility
.
.
.
Instructions
Unless otherwise specified all operands are vector-register operands. A “V” in the assembler syntax designates a vector operand. FIG. 14A depicts a table with example vector string instructions and characteristics and characteristics thereof, in accordance with aspects described herein.

Vector Find any Equal

FIG. 14B depicts an example VECTOR FIND ANY EQUAL instruction format, in accordance with aspects described herein. Proceeding from left to right, every unsigned binary integer element of the second operand is compared for equality with each unsigned binary integer element of the third operand and optionally zero if the Zero Search flag is set in the M5 field.

If the Result Type (RT) flag in the M5 field is zero, then for each element in the second operand that matches any element in the third operand, or optionally zero, the bit positions of the corresponding element in the first operand are set to ones, otherwise they are set to zero.

If the Result Type (RT) flag in the M5 field is one, then the byte index of the leftmost element in the second operand that matches an element in the third operand or zero is stored in byte seven of the first operand.

Each instruction has an Extended Mnemonic section which describe recommended extended mnemonics and their corresponding machine assembler syntax.

Programming Note:

For all instructions that optionally set the condition code, performance may be degraded if the condition code is set.
If the result Type (RT) flag in the M5 field is one and no bytes are found to be equal, or zero if the zero search flag is set, an index equal to the number of bytes in the vector is stored in byte seven of the first operand.
The M4 field specifies the element size control (ES). The ES control specifies the size of the elements in the vector register operands. If a reserved value is specified, a specification exception is recognized.
0—Byte
1—Halfword
2—Word
3-15—Reserved
FIG. 14C depicts an example format of the M5 field, in accordance with aspects described herein.
The bits of the M5 field are defined as follows:
Result Type (RT): If zero, each resulting element is a mask of all range comparisons on that element. If one, a byte index is stored into byte seven of the first operand and zeros are stored in all other elements.
Zero Search (ZS): If one, each element of the second operand is also compared to zero.
Condition Code Set (CC): If zero, the condition code is not set and remains unchanged. If one, the condition code is set as specified in the following section.
Special Conditions
A specification exception is recognized and no other action is taken if any of the following occurs:
1. The M4 field contains a value from 3-15.
2. Bit 0 of the M5 field are not zero.
Resulting Condition Code:
If the CC flag is zero, the code remains unchanged.
If the CC flag is one, the code is set as follows:













0
If the ZS-bit is set, there were no matches in a lower indexed



element than zero in the second operand.


1
Some elements of the second operand match at least one element



in the third operand


2
All elements of the second operand matched at least one element



in the third operand


3
No elements in the second operand match any elements in the third



operand









Program Exceptions:

1 Data with DXC FE, Vector Register

Operation if the vector-extension facility is not installed
Specification (Reserved ES value)
Transaction Constraint
Extended Mnemonics:















VFAEB
V1, V2, V3, M5
VFAE
V1, V2, V3, 0, M5


VFAEH
V1, V2, V3, M5
VFAE
V1, V2, V3, 1, M5


VFAEF
V1, V2, V3, M5
VFAE
V1, V2, V3, 2, M5


VFAEBS
V1, V2, V3, M5
VFAE
V1, V2, V3, 0, (M5 | X′1′)


VFAEHS
V1, V2, V3, M5
VFAE
V1, V2, V3, 1, (M5 | X′1′)


VFAEFS
V1, V2, V3, M5
VFAE
V1, V2, V3, 2, (M5 | X′1′)


VFAEZB
V1, V2, V3, M5
VFAE
V1, V2, V3, 0, (M5 | X′2′)


VFAEZH
V1, V2, V3, M5
VFAE
V1, V2, V3, 1, (M5 | X′2′)


VFAEZF
V1, V2, V3, M5
VFAE
V1, V2, V3, 2, (M5 | X′2′)


VFAEZBS
V1, V2, V3, M5
VFAE
V1, V2, V3, 0, (M5 | X′3′)


VFAEZHS
V1, V2, V3, M5
VFAE
V1, V2, V3, 1, (M5 | X′3′)


VFAEZFS
V1, V2, V3, M5
VFAE
V1, V2, V3, 2, (M5 | X′3′)









Vector Find Element Equal

FIG. 14D depicts an example VECTOR FIND ELEMENT EQUAL instruction format, in accordance with aspects described herein. Proceeding from left to right, the unsigned binary integer elements of the second operand are compared with the corresponding unsigned binary integer elements of the third operand. If two elements are equal, the byte index of the first byte of the leftmost equal element is placed in byte seven of the first operand. Zeros are stored in the remaining bytes of the first operand. If no bytes are found to be equal, or zero if the zero compare is set, then an index equal to the number of bytes in the vector is stored in byte seven of the first operand. Zeros are stored in the remaining bytes.

If the Zero Search (ZS) bit is set in the M5 field, then each element in the second operand is also compared for equality with zero. If a zero element is found in the second operand before any other elements of the second and third operands are found to be equal, the byte index of the first byte of the element found to be zero is stored in byte seven the first operand and zeros are stored in all other byte locations. If the Condition Code Set (CC) flag is one, then the condition code is set to zero.

The M4 field specifies the element size control (ES). The ES control specifies the size of the elements in the vector register operands. If a reserved value is specified, a specification exception is recognized.

0—Byte

1—Halfword

2—Word

3-15—Reserved

FIG. 14E depicts an example format of the M5 field, in accordance with aspects described herein.

The bits of the M5 field are defined as follows:

Reserved: Bits 0-1 are reserved and must be zero. Otherwise, a specification exception is recognized.
Zero Search (ZS): If one, each element of the second operand is also compared to zero.
Condition Code Set (CC): If zero, the condition code remains unchanged. If one, the condition code is set as specified in the following section.
Special Conditions
A specification exception is recognized and no other action is taken if any of the following occurs:
1. The M4 field contains a value from 3-15.
2. Bits 0-1 of the M5 field are not zero.
Resulting Condition Code:
If bit 3 of the M5 field is set to one, the code is set as follows:













0
If the zero compare bit is set, comparison detected a zero element in



the second operand in an element with a smaller index than any equal



comparisons.


1
Comparison detected a match between the second and third operands



in some element. If the zero compare bit is set, this match occurred



in an element with an index less than or equal to the zero comparing



element.


2
—


3
No elements compared equal.









If bit 3 of the M5 field is zero, the code remains unchanged.

Program Exceptions:

Data with DXC FE, Vector Register
Operation if the vector-extension facility is not installed
Specification (Reserved ES value)
Transaction Constraint
Extended Mnemonics:















VFEEB
V1, V2, V3, M5
VFEE
V1, V2, V3, 0, M5


VFEEH
V1, V2, V3, M5
VFEE
V1, V2, V3, 1, M5


VFEEF
V1, V2, V3, M5
VFEE
V1, V2, V3, 0, (M5 | X′1′)


VFEEHS
V1, V2, V3, M5
VFEE
V1, V2, V3, 1, (M5 | X′1′)


VFEEFS
V1, V2, V3, M5
VFEE
V1, V2, V3, 2, (M5 | X′1′)


VFEEZB
V1, V2, V3, M5
VFEE
V1, V2, V3, 0, (M5 | X′2′)


VFEEZH
V1, V2, V3, M5
VFEE
V1, V2, V3, 1, (M5 | X′2′)


VFEEZF
V1, V2, V3, M5
VFEE
V1, V2, V3, 2, (M5 | X′2′)


VFEEZBS
V1, V2, V3, M5
VFEE
V1, V2, V3, 0, (M5 | X′3′)


VFEEZHS
V1, V2, V3, M5
VFEE
V1, V2, V3, 1, (M5 | X′3′)


VFEEZFS
V1, V2, V3, M5
VFEE
V1, V2, V3, 2, (M5 | X′3′)









Programming Notes:

1. A byte index is always stored into the first operand for any element size. For example, if the element size was set to halfword and the 2nd indexed halfword compared equal, then a byte index of 4 would be stored.

2. The third operand should not contain elements with a value of zero. If the third operand does contain a zero and it matches with a zero element in the second operand before any other equal comparisons, condition code one is set regardless of the zero compare bit setting.

Vector Find Element not Equal

FIG. 14F depicts an example VECTOR FIND ELEMENT NOT EQUAL instruction format, in accordance with aspects described herein. Proceeding from left to right, the unsigned binary integer elements of the second operand are compared with the corresponding unsigned binary integer elements of the third operand. If two elements are not equal, the byte index of the left-most non-equal element is placed in byte seven of the first operand and zeros are stored to all other bytes. If the Condition Code Set (CC) bit in the M5 field is set to one, the condition code is set to indicate which operand was greater. If all elements were equal, then abyte index equal to the vector size is placed in byte seven of the first operand and zeros are placed in all other byte locations. If the CC bit is one, condition code three is set.

If the zero search (ZS) bit is set in the M5 field, each element in the second operand is also compared for equality with zero. If a zero element is found in the second operand before any other element of the second operand are found to be unequal, the byte index of the first byte of the element fount to be zero is stored in byte seven of the first operand. Zeros are stored in all other bytes and condition code 0 is set.

The M4 field specifies the element size control (ES). The ES control specifies the size of the elements in the vector register operands. If a reserved value is specified, a specification exception is recognized.

0—Byte

1—Halfword

2—Word

3-15—Reserved

FIG. 14G depicts an example format of the M5 field, in accordance with aspects described herein.

The bits of the M5 field are defined as follows:

Zero Search (ZS): If one, each element of the second operand is also compared to zero.
Condition Code Set (CC): If zero, the condition code is not set and remains unchanged. If one, the condition code is set as specified in the following section.
Special Conditions
A specification exception is recognized and no other action is taken if any of the following occurs:
1. The M4 field contains a value from 3-15.
2. Bits 0-1 of the M5 field are not zero.
Resulting Condition Code:
If bit 3 of the M5 field is set to one, the code is set as follows:













0
If the zero, compare bit is set, comparison detected a zero element in



both operands in a lower indexed element than any unequal compares


1
An element mismatch was detected and the element in VR2 is less



than the element in VR3


2
An element mismatch was detected and the element in VR2 is greater



than the element in VR3


3
All elements compared equa1, and if the zero compare bit is set,



no zero elements were found in the second operand.









If bit 3 of the M5 field is zero, the code remains unchanged.

Program Exceptions:

Data with DXC FE, Vector Register
Operation if the vector-extension facility is not installed
Specification (Reserved ES value)
Transaction Constraint
Extended Mnemonics:















VFENEB
V1, V2, V3, M5
VFENE
V1, V2, V3, 0, M5


VFENEH
V1, V2, V3, M5
VFENE
V1, V2, V3, 1, M5


VFENEF
V1, V2, V3, M5
VFENE
V1, V2, V3, 2, M5


VFENEBS
V1, V2, V3, M5
VFENE
V1, V2, V3, 0, (M5 | X′1′)


VFENEHS
V1, V2, V3, M5
VFENE
V1, V2, V3, 1, (M5 | X′1′)


VFENEFS
V1, V2, V3, M5
VFENE
V1, V2, V3, 2, (M5 | X′1′)


VFENEZB
V1, V2, V3, M5
VFENE
V1, V2, V3, 0, (M5 | X′2′)


VFENEZH
V1, V2, V3, M5
VFENE
V1, V2, V3, 1, (M5 | X′2′)


VFENEZF
V1, V2, V3, M5
VFENE
V1, V2, V3, 2, (M5 | X′2′)


VFENEZBS
V1, V2, V3, M5
VFENE
V1, V2, V3, 0, (M5 | X′3′)


VFENEZHS
V1, V2, V3, M5
VFENE
V1, V2, V3, 1, (M5 | X′3′)


VFENEZFS
V1, V2, V3, M5
VFENE
V1, V2, V3, 2, (M5 | X′3′)









Vector String Range Compare

FIG. 14H depicts an example VECTOR STRING RANGE COMPARE instruction format, in accordance with aspects described herein. Proceeding from left to right, the unsigned binary integer elements in the second operand are compared to ranges of values defined by even-odd pairs of elements in the third and fourth operands. The combined with control values from the fourth operand define the range of comparisons to be performed. If an element matches any of the ranges specified by the third and fourth operands, it is considered to be a match.

If the Result Type (RT) flag in the M6 field is zero, the bit positions of the element in the first operand corresponding to the element being compared in the second operand are set to one if the element matches any of the ranges, otherwise they are set to zero.

If the Result Type (RT) flag in the M6 field is set to one, the byte index of the first element in the second operand that matches any of the ranges specified by the third and fourth operands or a zero comparison, if the ZS flag is set to one, is placed in byte seven of the first operand and zeros are stored in the remaining bytes. If no elements match, then an index equal to the number of bytes in a vector is placed in byte seven of the first operand and zeros are stored in the remaining bytes.

The Zero Search (ZS) flag in the M6 field, if set to one, will add a comparison to zero of the second operand elements to the ranges provided by the third and fourth operands. If a zero comparison in a lower indexed element than any other true comparison, then the condition code is set to zero.

The operands contain elements of the size specified by the Element Size control in the M5 field.

The fourth operand elements have the following format:

If ES equals 0, the fourth operand elements have the example format as shown in FIG. 14I.

If ES equals 1, the fourth operand elements have the example format as shown in FIG. 14J.

If ES equals 2, the fourth operand elements have the example format as shown in FIG. 14K.

The bits in the fourth operand elements are defined as follows:

Equal (EQ): When one a comparison for equality is made.
Greater Than (GT): When one a greater than comparison is performed.
Less Than (LT): When one a less than comparison is performed.
All other bits are reserved and should be zero to ensure future compatibility.
The control bits may be used in any combination. If none of the bits are set, the comparison will always produce a false result. If all of the bits are set, the comparison will always produce a true result.
The M5 field specifies the element size control (ES). The ES control specifies the size of the elements in the vector register operands. If a reserved value is specified, a specification exception is recognized.
0—Byte
1—Halfword
2—Word
3-15—Reserved
FIG. 14L depicts an example format of the M6 field, in accordance with aspects described herein.
The bits of the M6 field are defined as follows:
Invert Result (IN): If zero, the comparison proceeds with the pair of values in the control vector. If one, the result of the pairs of the comparisons in the ranges are inverted.
Result Type (RT): If zero, each resulting element is a mask of all range comparisons on that element. If one, an index is stored into byte seven of the first operand. Zeroes are stored in the remaining bytes.
Zero Search (ZS): If one, each element of the second operand is also compared to zero.
Condition Code Set (CC): If zero, the condition code is not set and remains unchanged. If one, the condition code is set as specified in the following section.
Special Conditions
A specification exception is recognized and no other action is taken if any of the following occurs:
1. The M4 field contains a value from 3-15.
Resulting Condition Code:













0
If ZS = 1 and a zero is found in a lower indexed element than



any compare


1
Comparison found


2
—


3
No comparison found









Program Exceptions:

Data with DXC FE, Vector Register
Operation if the vector-extension facility is not installed
Specification (Reserved ES value)
Transaction Constraint
Extended Mnemonics:















VSTRCB
V1, V2, V3, V4, M6
VSTRC
V1, V2, V3, V4, 0, M6


VSTRCH
V1, V2, V3, V4, M6
VSTRC
V1, V2, V3, V4, 1, M6


VSTRCF
V1, V2, V3, V4, M6
VSTRC
V1, V2, V3, V4, 2, M6


VSTRCBS
V1, V2, V3, V4, M6
VSTRC
V1, V2, V3, V4, 0, (M6 | X′1′)


VSTRCHS
V1, V2, V3, V4, M6
VSTRC
V1, V2, V3, V4, 1, (M6 | X′1′)


VSTRCFS
V1, V2, V3, V4, M6
VSTRC
V1, V2, V3, V4, 2, (M6 | X′1′)


VSTRCZB
V1, V2, V3, V4, M6
VSTRC
V1, V2, V3, V4, 0, (M6 | X′2′)


VSTRCZH
V1, V2, V3, V4, M6
VSTRC
V1, V2, V3, V4, 1, (M6 | X′2′)


VSTRCZF
V1, V2, V3, V4, M6
VSTRC
V1, V2, V3, V4, 2, (M6 | X′2′)


VSTRCZBS
V1, V2, V3, V4, M6
VSTRC
V1, V2, V3, V4, 0, (M6 | X′3′)


VSTRCZHS
V1, V2, V3, V4, M6
VSTRC
V1, V2, V3, V4, 1, (M6 | X′3′)


VSTRCZFS
V1, V2, V3, V4, M6
VSTRC
V1, V2, V3, V4, 2, (M6 | X′3′)









FIG. 14M depicts an example truth table in connection with the VECTOR STRING RANGE COMPARE instruction, in accordance with aspects described herein.

Load Count to Block Boundary

FIG. 14N depicts an example LOAD COUNT TO BLOCK BOUNDARY instruction format, in accordance with aspects described herein. A 32-bit unsigned binary integer containing the number of bytes possible to load from the second operand location without crossing a specified block boundary, capped at sixteen is placed in the first operand.

The displacement is treated as a 12-bit unsigned integer.

The second operand address is not used to address data.

The M3 field specifies a code that is used to signal the CPU as to the block boundary size to compute the number of possible bytes loaded. If a reserved value is specified then a specification exception is recognized.

Code Boundary

0 64-Byte

1 128-Byte

2 256-Byte

3 512-Byte

4 1K-Byte

2K-Byte

6 4K-Byte

7-15 Reserved

Resulting Condition Code:

















0
Operand one is sixteen



1
—



2
—



3
Operand one less than sixteen










Resulting Condition Code:

Program Exceptions:

Operation if the vector-extension facility is not installed
Specification
Programming Note:
It is expected that LOAD COUNT TO BLOCK BOUNDARY will be used in conjunction with VECTOR LOAD TO BLOCK BOUNDARY to determine the number of bytes that were loaded.
Vector Load GR from VR Element
FIG. 14O depicts an example VECTOR LOAD GR FROM VR ELEMENT instruction format, in accordance with aspects described herein. The element of the third operand of size specified by the ES value in the M4 field and indexed by the second operand address is placed in the first operand location. The third operand is a vector register. The first operand is a general register. If the index specified by the second operand address is greater than the highest numbered element in the third operand, of the specified element size, the data in the first operand is unpredictable.

If the vector register element is smaller than a doubleword, the element is right aligned in the 64-bit general register and zeros fill the remaining bits.

The second operand address is not used to address data; instead the rightmost 12 bits of the address are used to specify the index of an element within the second operand.

The M4 field specifies the element size control (ES). The ES control specifies the size of the elements in the vector register operands. If a reserved value is specified, a specification exception is recognized.

0—Byte

1—Halfword

2—Word

3—Doubleword

4-15—Reserved unchanged.

Resulting Condition Code: The code is unchanged.

Program Exceptions:

Data with DXC FE, Vector Register
Operation if the vector-extension facility is not installed
Specification (Reserved ES value)
Transaction Constraint
Extended Mnemonics:















VLGVB
R1, V3, D2(B2)
VLGV
R1, V3, D2(B2), 0


VLGVH
R1, V3, D2(B2)
VLGV
R1, V3, D2(B2), 1


VLGVF
R1, V3, D2(B2)
VLGV
R1, V3, D2(B2), 2


VLGVG
R1, V3, D2(B2)
VLGV
R1, V3, D2(B2), 3









Vector Load to Block Boundary

FIG. 14P depicts an example VECTOR LOAD TO BLOCK BOUNDARY instruction format, in accordance with aspects described herein. The first operand is loaded starting at the zero indexed byte element with bytes from the second operand. If a boundary condition is encountered, the rest of the first operand is unpredictable. Access exceptions are not recognized on bytes not loaded.

The displacement for VLBB is treated as a 12-bit unsigned integer.

The M3 field specifies a code that is used to signal the CPU as to the block boundary size to load to. If a reserved value is specified, a specification exception is recognized.

Code Boundary

0 64-Byte

1 128-Byte

2 256-Byte

3 512-Byte

4 1K-Byte

5 2K-Byte

6 4K-Byte

7-15 Reserved

Resulting Condition Code: The code remains unchanged.

Program Exceptions:

Access (fetch, operand 2)
Data with DXC FE, Vector Register
Operation if the vector-extension facility is not installed
Specification (Reserved Block Boundary Code)
Transaction Constraint
Programming Notes:
1. In certain circumstances data may be loaded past the block boundary. However, this will only occur if there are no access exceptions on that data.
Vector Store
FIG. 14Q depicts an example VECTOR STORE instruction format, in accordance with aspects described herein. The 128-bit value in the first operand is stored to the storage location specified by the second operand. The displacement for VST is treated as a 12-bit unsigned integer.

Resulting Condition Code: The code remains unchanged.

Program Exceptions:

Access (store, operand 2)
Data with DXC FE, Vector Register
Operation if the vector-extension facility is not installed
Transaction Constraint
Vector Store with Length
FIG. 14R depicts an example VECTOR STORE WITH LENGTH instruction format, in accordance with aspects described herein. Proceeding from left to right, bytes from the first operand are stored at the second operand location. The general register specified third operand contains a 32-bit unsigned integer containing a value that represents the highest indexed byte to store. If the third operand contains a value greater than or equal to the highest byte index of the vector, all bytes of the first operand are stored.

Access exceptions are only recognized on bytes stored.

The displacement for VECTOR STORE WITH LENGTH is treated as a 12-bit unsigned integer.

Resulting Condition Code: The condition code remains unchanged.

Program Exceptions:

Access (store, operand 2)
Data with DXC FE, Vector Register
Operation if the vector-extension facility is not installed
Transaction Constraint
RXB Description
All vector instructions have a field in bits 36-40 of the instruction labeled as RXB. This field contains the most significant bits for all of the vector register designated operands. Bits for register designations not specified by the instruction are reserved and should be set to zero; otherwise, the program may not operate compatibly in the future. The most significant bit is concatenated to the left of the four-bit register designation to create the five-bit vector register designation.

The bits are defined as follows:

0. Most significant bit for the vector register designation in bits 8-11 of the instruction.

1. Most significant bit for the vector register designation in bits 12-15 of the instruction.

2. Most significant bit for the vector register designation in bits 16-19 of the instruction.

3. Most significant bit for the vector register designation in bits 32-35 of the instruction.

Vector Enablement Control

The vector registers and instructions may only be used if both the vector enablement control (bit 46) and the AFP-register-control (bit 45) in control register zero are set to one. If the vector facility is installed and a vector instruction is executed without the enablement bits set, a data exception with DXC FE hex is recognized. If the vector facility is not installed, an operation exception is recognized.

## Claims

1. A computer program product for executing a machine instruction in a central processing unit, the computer program product comprising:
a non-transitory computer readable storage medium readable by a processing circuit and storing instructions for execution by the processing circuit for performing a method comprising:
obtaining, by a processor, a machine instruction for execution, the machine instruction being defined for computer execution according to a computer architecture, the machine instruction comprising:
at least one opcode field to provide an opcode, the opcode identifying a Load Count to Block Boundary operation;
a register field to be used to designate a register, the register comprising a first operand; and
at least one field for indicating a location of a second operand, the second operand comprising at least a portion of a block of main memory; and

executing the machine instruction, the execution comprising:
determining a distance from the location of the second operand to a boundary of the block of main memory, wherein the location of the second operand is a starting address in memory from which data is to be counted, wherein the determining the distance comprises determining an ending address at which the counting is to stop, and wherein the determining the ending address comprises computing the ending address as follows:
ending address=minimum of (starting address+(boundary size−(starting address AND NOT boundary mask)), starting address+register size), wherein the boundary size is the boundary, boundary mask is equal to 0−boundary size, and register size is a length of a selected register; and

based on determining the distance, placing a value representing the determined distance in the first operand.

2. The computer program product of claim 1, wherein the machine instruction further comprises a mask field, the mask field specifying the boundary.

3. The computer program product of claim 2, wherein the block boundary is one boundary of a plurality of boundaries specifiable by the mask field.

4. The computer program product of claim 1, wherein the executing further comprises dynamically determining the boundary, the dynamically determining using a specified type of boundary and one or more characteristics of the processor.

5. The computer program product of claim 1, wherein the at least one field comprises a displacement field, a base field and an index field, the base field and index field for locating general registers having contents to be added to contents of the displacement field to form an address of the second operand, the address of the second operand providing the location of the second operand.

6. A computer system for executing a machine instruction in a central processing unit, the computer system comprising:
a memory; and
a processor in communications with the memory, wherein the computer system is configured to perform a method, the method comprising:
obtaining, by a processor, a machine instruction for execution, the machine instruction being defined for computer execution according to a computer architecture, the machine instruction comprising:
at least one opcode field to provide an opcode, the opcode identifying a Load Count to Block Boundary operation;
a register field to be used to designate a register, the register comprising a first operand; and
at least one field for indicating a location of a second operand, the second operand comprising at least a portion of a block of main memory; and

executing the machine instruction, the execution comprising:
determining a distance from the location of the second operand to a boundary of the block of main memory, wherein the location of the second operand is a starting address in memory from which data is to be counted, wherein the determining the distance comprises determining an ending address at which the counting is to stop, and wherein the determining the ending address comprises computing the ending address as follows:
ending address=minimum of (starting address+(boundary size−(starting address AND NOT boundary mask)), starting address+register size), wherein the boundary size is the boundary, boundary mask is equal to 0−boundary size, and register size is a length of a selected register; and

based on determining the distance, placing a value representing the determined distance in the first operand.

7. The computer system of claim 6, wherein the machine instruction further comprises a mask field, the mask field specifying the boundary.

8. The computer system of claim 6, wherein the executing further comprises dynamically determining the boundary, the dynamically determining using a specified type of boundary and one or more characteristics of the processor.

9. The computer program product of claim 1, wherein the boundary is an end boundary of the block of main memory.

10. The computer system of claim 6, wherein the boundary is an end boundary of the block of main memory.