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Pull in r248439 from upstream llvm trunk (by Sanjay Patel):

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set div/rem default values to 'expensive' in TargetTransformInfo's
  cost model

  ...because that's what the cost model was intended to do.

  As discussed in D12882, this fix has a temporary unintended
  consequence for SimplifyCFG: it causes us to not speculate an fdiv.
  However, two wrongs make PR24818 right, and two wrongs make PR24343
  act right even though it's really still wrong.

  I intend to correct SimplifyCFG and add to CodeGenPrepare to account
  for this cost model change and preserve the righteousness for the bug
  report cases.

  https://llvm.org/bugs/show_bug.cgi?id=24818
  https://llvm.org/bugs/show_bug.cgi?id=24343

  Differential Revision: http://reviews.llvm.org/D12882

This fixes the too-eager fdiv hoisting in pow(), which could lead to
unexpected floating point exceptions.
This commit is contained in:
dim 2015-09-24 21:20:00 +00:00
parent eebb6d6061
commit a16871dddc
1 changed files with 8 additions and 0 deletions
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8
contrib/llvm/include/llvm/Analysis/TargetTransformInfoImpl.h
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@ -60,6 +60,14 @@ class TargetTransformInfoImplBase {
// Otherwise, the default basic cost is used.
return TTI::TCC_Basic;
case Instruction::FDiv:
case Instruction::FRem:
case Instruction::SDiv:
case Instruction::SRem:
case Instruction::UDiv:
case Instruction::URem:
return TTI::TCC_Expensive;
case Instruction::IntToPtr: {
// An inttoptr cast is free so long as the input is a legal integer type
// which doesn't contain values outside the range of a pointer.