Instruction execution control system

Abstract: The instruction execution control system of an information processing device having a pipeline instruction execution control portion is provided for sequentially executing an instruction interval between a completion of execution of a certain instruction and a read out of a next instruction. This system comprises program status word holding means (2) for holding program status word including indicating information concerning whether or not an instruction interval is to be sequentially executed and control information indicating execution status of program, and instruction execution sequencing indication means (4) responsive to the indicating information of the program status word held in the program status word holding means (2) for indicating the instruction execution control portion whether or not the instructions in the interval are to be sequentially executed. In this system an instruction in which program exception occurs can be easily identified, and a sequential execution of instruction interval between a completion of execution of a certain instruction and a readout of a next instruction only within a desired portion of a specific program can be easily performed.

Description: The present invention relates to an execution control system for use in a pipeline instruction execution control type information processing device, in which an instruction interval between a completion of a certain instruction used in, for example, debug processing and a readout of a next instruction is executed by sequencing them. Sequential control which is a basic scheme of execution control operates in steps of readout of an instruction, decoding thereof, execution thereof and, then, readout of next instruction. On the other hand, an execution control using pipeline system is performed as follows: that is, an instruction which is considered as necessary in the future or instruction which has been executed recently is stored in an instruction buffer, and the instruction is fetched ahead. The fetched instruction is partially decoded, a portion of processing is performed in parallel to an execution of a current instruction, several instructions are preproccessed in parallel simultaneously. A system for execution of instructions in between a completion of execution of a certain instruction and a readout of a next instruction is usually used in debugging. Therefore, the execution is controlled by an indication from a service processor. It is assumed in the pipeline instruction execution control type information processor that a program exception occurs during execution of a program. Since, in the information processor of this type, a plurality of instructions are executed in parallel simultaneously by the pipeline system, it is difficult to identify a program in which such program exception occurred. Even in a conventional system for sequentially executing the instructions, an instruction execution control portion is indicated through the service processor to execute these instructions sequentially. Therefore, the instruction interval is executed sequentially by the information processing device as a whole. Therefore, when a plurality of programs are being processed by the information processing device, it is impossible to sequentially execute the instruction interval in only a desired portion of a specific program. EP-A-0 042 442 discloses an information processing system including a scalar arithmetic unit and a vector arithmetic unit. A group of instructions can be processed in parallel by the scalar arithmetic unit and the vector arithmetic unit. A control register supervises the content of the instruction register and makes its parallel/serial processing mode bit logic "1" or "0". US-A-4 251 859 discloses a defeat overlap instruction which will invalidate partial operations of succeeding instructions, if the partial operations are processed in parallel and in overlapping relationship with the defeat overlap instruction. An object of the present invention is to eliminate the above mentioned problem by providing an instruction execution control system by which an instruction in which program exception occurs can be easily identified and a sequential execution of instruction interval between a completion of execution of a certain instruction and a readout of a next instruction only within a desired portion of a specific program can be easily performed. This object is solved with the features of the claims. Other features, constructions and advantages of the present invention will become apparent from reading the following description with reference to the accompanying drawings in which same or corresponding components are depicted by same reference numerals, respectively, and in which, Fig. 1 shows a system to which an embodiment of the present invention is applied; Fig. 2 shows a relationship between a flow of program and a content of an instruction execution sequencing mode indicating information 3 held in a program status word holding portion 2; Fig. 3 is a diagram showing positions on the program in Fig. 2 to which a sequencing mode setting instruction and a sequencing mode resetting instruction are inserted; Fig. 4 is a diagram showing positions on the program in Fig. 2 to which instruction execution sequencing instructions are inserted; Fig. 5 shows a portion of an embodiment of the present invention; and Figs. 6A and 6B illustrate a processing sequence of interrupt routine used in an embodiment of the present invention. Referring to Fig. 1, a system to which an embodiment of the present invention is applied includes a main memory 5 for storing at least instruction word or data, an instruction cache memory 6 for storing at least a portion of a copy of the instruction word stored in the main memory 5, an instruction execution control portion 1 for executing an instruction fetched from the instruction cache memory 6 by means of a pipeline system, a program status word holding portion 2 containing an instruction execution sequencing mode indicating information 3 for holding a control information indicative of an execution status of program as a program status word and an instruction execution sequencing indication portion 4 responsive to a content of the instruction execution sequencing mode instruction information 3 of the program status word held in the program status word holding portion 2 for indicating the instruction execution control portion 1 to sequentially execute an instruction interval between a completion of execution of a certain instruction and a read of a next instruction. Referring to Fig. 2, a relation between a source program flow and the content of the instruction execution sequencing mode indicating information 3 held in the program status word holding portion 2 is shown. When it is desired to sequentially execute the instruction interval within a period between points A and B on the source program flow, it is enough, in the present invention, to set the instruction execution sequencing mode indicating information 3 in the program status word holding portion 2 to a logical "1". The setting of the instruction execution sequencing mode indicating information 3 to "1" can be performed by either of the following two methods. The first method will be described first in detail with reference to Figs. 2, 3 and 5. When the instruction interval is to be sequentially executed in the period between the points A and B on the source program flow shown in Fig. 2, a sequencing mode setting instruction and a sequencing mode resetting instruction are inserted into the points A and B of the program shown in Fig. 3, respectively. Referring to Figs. 3 and 5, when the sequencing mode setting instruction is executed in the instruction execution control portion 1, the instruction execution sequencing mode indicating information 3 in the program status word holding portion 2 is set to "1" by a setting means 11. Upon this "1" state of the sequencing mode indicating information 3, the instruction execution sequencing indicating portion 4 sends an instruction to the instruction execution control portion 1. The instruction execution control portion 1 is set to an instruction execution sequencing mode by this instruction and the instruction interval is then sequentially executed. Further, when the source program is executed up to the point B in Fig. 3, the sequencing mode resetting instruction is executed. In response to this execution, the instruction execution sequencing mode indicating information 3 in the program status word holding portion 2 is changed to "0". With this change of the status to "0", the instruction sequencing indication portion 4 indicates the instruction execution control portion 1 to reset the instruction execution sequencing mode. Upon this instruction, the instruction execution control portion 1 pipelines the instruction interval and executes it. The second method for setting the instruction execution sequencing mode indicating information 3 will be described in detail with reference to Figs. 2, 4 and 6. When the instruction interval is sequentially executed in the period between the points A and B on the source program flow shown in Fig. 2, instruction execution sequencing instructions are inserted into the points A and B of the source program flow shown in Fig. 4. The source program is compiled by a compiler upon a detection of the instruction execution sequencing instruction such that interrupt routines A and B are called at the points A and B on the source program flow. These interrupt routines are those for switching the mode of sequencing and execution of the instruction interval. A processing of the interrupt routine will be described in detail with reference to Figs. 6A and 6B. Referring to Fig. 6A, a basic process status (BPSX) is saved in a process status block (PSB) of a memory assigned by a current process status block address (CPSB). Referring to Fig. 6B, the basic process status (BPSY) is reloaded from the process status block (PSB) of the memory assigned by a next process status block address (NPSB). At this time, the program status word is contained in the basic process status (BPSX and BPSY), saved in the process status block (PSB) of the memory and reloaded. Referring to Figs. 6A and 6B, the interrupt routine A is to rewrite the content of the interval instruction sequencing mode indicating information 3 of the program status word in the basic process status (BPSX) which is saved at the calling time of the interrupt routine A by a called process to "1" so that the instruction interval is put into the sequencing and execution mode. At the same time, the basic process status (BPSX) is rewritten to the basic process status ((BPSY) or an address (CPSB) of the BPSX is rewritten to an address (NPSB) of the BPSY. When the control is returned to the called process, the basic process status (BPSY) is reloaded to the process and the saved program status word is recovered. At this time, the interval instructions sequencing mode indicating information 3 in the program status word indicates the instruction interval sequencing execution mode. On the contrary, the interrupt routine B rewrites the interval instruction sequencing mode indicating information 3 in the program status word in the basic process status BPSX which is saved at the calling time of the interrupt routine B by the called process to a content indicating a mode in which the interval instruction is not sequentially executed. At the same time, the basic process status (BPSY) is shifted to the basic process status (BPSX) or an address (CPSB) of the BPSY is rewritten to an address (NPSB) of the BPSX. When the control is returned to the called process, the basic process status (BPSY) is reloaded to the process and the saved program status word is recovered. At this time, the interval instruction sequencing mode indicating information 3 of the program status word indicates a mode in which the instruction interval is not sequenced and executed. By executing the compiled program shown in Fig. 4, the instruction interval is sequenced and executed in the period between the points A and B on the program shown in Fig. 4. According to the present invention, when a program exception occurs during an execution of a program in a pipeline instruction execution control type information processing device, a plurality of instructions are executed in parallel simultaneously by a pipeline system. Therefore, when it is necessary to identify a particular instruction in which the program exception occurs or when the instruction interval should be sequentially executed, the particular instruction can be easily identified without necessity of sequencing and executing the instruction interval by the whole information processing device, by setting in the program status word an instruction information indicating whether or not the instruction interval is to be sequentially executed. Even when a plurality of programs are being processed by the information processing device, the instruction interval can be sequentially executed in only a desired portion of a specific program.

Claims: An instruction execution control system for sequential executing each instruction in a block of succeeding instructions of program in an information processing device having an instruction execution control portion (1) utilizing a pipeline system, characterized by comprising program status word holding means (2) for holding a program status word including an indicating information indicating said each instruction is to be executed in a non-pipeline control or in the normal pipeline control, and a control information showing an execution status of a program and instruction execution sequencing indication means (4) responsive to said indicating information of said program status word held in said program status word holding means (2) to give said instruction execution control portion an indication whether said each instruction is to be executed in a non-pipeline control or in the normal pipeline control. The system as claimed in claim 1, characterized in that said instruction execution sequencing indication means (4) comprises setting means (11) responsive to an indication from said instruction execution control portion to set said indicating information of said program status word holding means (2) so as to sequentially execute said each instruction and resetting means (12) responsive to an indication from said instruction execution control portion so as to reset said indicating information set by said setting means (11).

Inventors: INOUE KAZUHISA, INOUE, KAZUHISA
Applicants: NIPPON ELECTRIC CO, NEC CORPORATION
Application year: 1990
Main classification: G06F9
IPC codes: G06F9, G06F11