Teach TailRecursionElimination to handle certain cases of nocapture escaping allocas.

Without the changes introduced into this patch, if TRE saw any allocas at all,
TRE would not perform TRE *or* mark callsites with the tail marker.

Because TRE runs after mem2reg, this inadequacy is not a death sentence. But
given a callsite A without escaping alloca argument, A may not be able to have
the tail marker placed on it due to a separate callsite B having a write-back
parameter passed in via an argument with the nocapture attribute.

Assume that B is the only other callsite besides A and B only has nocapture
escaping alloca arguments (*NOTE* B may have other arguments that are not passed
allocas). In this case not marking A with the tail marker is unnecessarily
conservative since:

  1. By assumption A has no escaping alloca arguments itself so it can not
     access the caller's stack via its arguments.

  2. Since all of B's escaping alloca arguments are passed as parameters with
     the nocapture attribute, we know that B does not stash said escaping
     allocas in a manner that outlives B itself and thus could be accessed
     indirectly by A.

With the changes introduced by this patch:

  1. If we see any escaping allocas passed as a capturing argument, we do
     nothing and bail early.

  2. If we do not see any escaping allocas passed as captured arguments but we
     do see escaping allocas passed as nocapture arguments:

       i. We do not perform TRE to avoid PR962 since the code generator produces
          significantly worse code for the dynamic allocas that would be created
          by the TRE algorithm.

       ii. If we do not return twice, mark call sites without escaping allocas
           with the tail marker. *NOTE* This excludes functions with escaping
           nocapture allocas.

  3. If we do not see any escaping allocas at all (whether captured or not):

       i. If we do not have usage of setjmp, mark all callsites with the tail
          marker.

       ii. If there are no dynamic/variable sized allocas in the function,
           attempt to perform TRE on all callsites in the function.

Based off of a patch by Nick Lewycky.

rdar://14324281.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@186057 91177308-0d34-0410-b5e6-96231b3b80d8
SLPVectorizer: refactor the code that places extracts. Place the code that decides where to put extracts in the build-tree phase. This allows us to take the cost of the extracts into account.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@186058 91177308-0d34-0410-b5e6-96231b3b80d8
Consolidate some of the lit tests.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@186060 91177308-0d34-0410-b5e6-96231b3b80d8
Consolidate some of the lit tests.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@186062 91177308-0d34-0410-b5e6-96231b3b80d8
Consolidate more lit tests.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@186063 91177308-0d34-0410-b5e6-96231b3b80d8
Fix a warning.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@186064 91177308-0d34-0410-b5e6-96231b3b80d8
Fix indentation. No functional change.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@186065 91177308-0d34-0410-b5e6-96231b3b80d8
RegScavenger should not exclude undef uses

When computing currently-live registers, the register scavenger excludes undef
uses. As a result, undef uses are ignored when computing the restore points of
registers spilled into the emergency slots. While the register scavenger
normally excludes from consideration, when scavenging, registers used by the
current instruction, we need to not exclude undef uses. Otherwise, we might end
up requiring more emergency spill slots than we have (in the case where the
undef use *is* the currently-spilled register).

Another bug found by llvm-stress.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@186067 91177308-0d34-0410-b5e6-96231b3b80d8
Initialize AsmPrinter::MF in the constructor

MF is normally initialized in AsmPrinter::SetupMachineFunction, but if the file
contains only globals (no functions), then we need this to be initialized
because, when encountering an error, lowerConstant() references it.

This should fix the non-deterministic failures of
test/CodeGen/X86/nonconst-static-iv.ll, etc.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@186068 91177308-0d34-0410-b5e6-96231b3b80d8
TryToSimplifyUncondBranchFromEmptyBlock was checking that any common
predecessors of the two blocks it is attempting to merge supply the
same incoming values to any phi in the successor block.  This change
allows merging in the case where there is one or more incoming values
that are undef.  The undef values are rewritten to match the non-undef
value that flows from the other edge.  Patch by Mark Lacey.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@186069 91177308-0d34-0410-b5e6-96231b3b80d8
[SystemZ] Allow 8-bit operands to RISBG

RISBG has three 8-bit operands (I3, I4 and I5).  I'd originally
restricted all three to 6 bits, since that's the only range we intended
to use at the time.  However, the top bit of I4 acts as a "zero" flag for
RISBG, while the top bit of I3 acts as a "test" flag for RNSBG & co.
This patch therefore allows them to have the full 8-bit range.
I've left the fifth operand as a 6-bit value for now since the
upper 2 bits have no defined meaning.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@186070 91177308-0d34-0410-b5e6-96231b3b80d8
[SystemZ] Use zeroing form of RISBG for some AND sequences

RISBG can handle some ANDs for which no AND IMMEDIATE exists.
It also acts as a three-operand AND for some cases where an
AND IMMEDIATE could be used instead.

It might be worth adding a pass to replace RISBG with AND IMMEDIATE
in cases where the register operands end up being the same and where
AND IMMEDIATE is smaller.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@186072 91177308-0d34-0410-b5e6-96231b3b80d8
[SystemZ] Use zeroing form of RISBG for shift-and-AND sequences

Extend r186072 to handle shifts and ANDs.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@186073 91177308-0d34-0410-b5e6-96231b3b80d8
[SystemZ] Add testcase missing from r186073


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@186074 91177308-0d34-0410-b5e6-96231b3b80d8
Reduce the number of indirections in the attributes implementation.

- Coallocate entires for AttributeSetImpls and Nodes after the class itself.
- Remove mutable iterators from immutable classes.
- Remove unused context field from AttributeImpl.
- Derive Enum/Align/String attribute implementations from AttributeImpl instead
  of having a whole new inheritance tree for them.
- Derive AlignAttributeImpl from EnumAttributeImpl.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@186075 91177308-0d34-0410-b5e6-96231b3b80d8
Sync llvm-ar's help string with the options it supports.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@186076 91177308-0d34-0410-b5e6-96231b3b80d8
Remove support for truncating names in archives.

* All systems we support have some form of long name support.
* The options has different names and semantics in different implementations
  ('f' on gnu, 'T' on OS X), which makes it unlikely it is normally used on
  build systems.
* It was completely untested.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@186078 91177308-0d34-0410-b5e6-96231b3b80d8
Delete dead code.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@186079 91177308-0d34-0410-b5e6-96231b3b80d8
Remove the 'N' modifier from llvm-ar.

* It is not present on OS X.
* It is untested.
* It is not needed for using ar in a build system.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@186080 91177308-0d34-0410-b5e6-96231b3b80d8
Add tests for the 'x' operation.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@186081 91177308-0d34-0410-b5e6-96231b3b80d8