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| author | Dan Gohman <gohman@apple.com> | 2009-08-12 16:37:02 +0000 |
|---|---|---|
| committer | Dan Gohman <gohman@apple.com> | 2009-08-12 16:37:02 +0000 |
| commit | 9ca9daad2175cd57776e7de7fb6f78eb96fc7445 (patch) | |
| tree | 944d50d12cbc814a179260471312972297a06d3e /lib/Transforms/Scalar/InstructionCombining.cpp | |
| parent | fa94b948d9a0aaaad98901815e56b676803ad259 (diff) | |
Transform -X/C to X/-C, implementing a README.txt entry.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@78812 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'lib/Transforms/Scalar/InstructionCombining.cpp')
| -rw-r--r-- | lib/Transforms/Scalar/InstructionCombining.cpp | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp index 669ef2d516..b875420e5b 100644 --- a/lib/Transforms/Scalar/InstructionCombining.cpp +++ b/lib/Transforms/Scalar/InstructionCombining.cpp @@ -3077,6 +3077,14 @@ Instruction *InstCombiner::visitSDiv(BinaryOperator &I) { RHS->getValue().exactLogBase2()); return BinaryOperator::CreateAShr(Op0, ShAmt, I.getName()); } + + // -X/C --> X/-C provided the negation doesn't overflow. + if (SubOperator *Sub = dyn_cast<SubOperator>(Op0)) + if (isa<Constant>(Sub->getOperand(0)) && + cast<Constant>(Sub->getOperand(0))->isNullValue() && + Sub->hasNoSignedOverflow()) + return BinaryOperator::CreateSDiv(Sub->getOperand(1), + ConstantExpr::getNeg(RHS)); } // If the sign bits of both operands are zero (i.e. we can prove they are |