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Reprioritize tests for tail duplication to be aggressive about indirect

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branches even when optimizing for code size.  Unless we find evidence to the
contrary in the future, the special treatment for indirect branches does not
have a significant effect on code size, and performance still matters with -Os.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@90147 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Bob Wilson 2009-11-30 18:56:45 +00:00
parent 15217e63bc
commit 3858225afc
1 changed files with 3 additions and 3 deletions
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6
lib/CodeGen/TailDuplication.cpp
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@ -116,14 +116,14 @@ bool TailDuplicatePass::TailDuplicate(MachineBasicBlock *TailBB,
// duplicate only one, because one branch instruction can be eliminated to // duplicate only one, because one branch instruction can be eliminated to
// compensate for the duplication. // compensate for the duplication.
unsigned MaxDuplicateCount; unsigned MaxDuplicateCount;
if (MF.getFunction()->hasFnAttr(Attribute::OptimizeForSize)) if (!TailBB->empty() && TailBB->back().getDesc().isIndirectBranch())
MaxDuplicateCount = 1;
else if (!TailBB->empty() && TailBB->back().getDesc().isIndirectBranch())
// If the target has hardware branch prediction that can handle indirect // If the target has hardware branch prediction that can handle indirect
// branches, duplicating them can often make them predictable when there // branches, duplicating them can often make them predictable when there
// are common paths through the code. The limit needs to be high enough // are common paths through the code. The limit needs to be high enough
// to allow undoing the effects of tail merging. // to allow undoing the effects of tail merging.
MaxDuplicateCount = 20; MaxDuplicateCount = 20;
else if (MF.getFunction()->hasFnAttr(Attribute::OptimizeForSize))
MaxDuplicateCount = 1;
else else
MaxDuplicateCount = TailDuplicateSize; MaxDuplicateCount = TailDuplicateSize;