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| author | Eli Friedman <eli.friedman@gmail.com> | 2010-01-31 02:30:23 +0000 |
|---|---|---|
| committer | Eli Friedman <eli.friedman@gmail.com> | 2010-01-31 02:30:23 +0000 |
| commit | 694488f4770468f03b974180631c0fbfa21b28cc (patch) | |
| tree | ff3af0445dfed3464a6c36bf37a5f8736a12097e /lib/Transforms | |
| parent | 894c1af05fb3f0d8e2ee6565816fa220b260ed9d (diff) | |
| download | external_llvm-694488f4770468f03b974180631c0fbfa21b28cc.zip external_llvm-694488f4770468f03b974180631c0fbfa21b28cc.tar.gz external_llvm-694488f4770468f03b974180631c0fbfa21b28cc.tar.bz2 | |
Add a small transform: transform -(X<<Y) to (-X<<Y) when the shift has a single
use and X is free to negate.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@94941 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'lib/Transforms')
| -rw-r--r-- | lib/Transforms/InstCombine/InstCombineAddSub.cpp | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/lib/Transforms/InstCombine/InstCombineAddSub.cpp b/lib/Transforms/InstCombine/InstCombineAddSub.cpp index 4891ff0..119b1ca 100644 --- a/lib/Transforms/InstCombine/InstCombineAddSub.cpp +++ b/lib/Transforms/InstCombine/InstCombineAddSub.cpp @@ -676,6 +676,13 @@ Instruction *InstCombiner::visitSub(BinaryOperator &I) { return BinaryOperator::CreateSDiv(Op1I->getOperand(0), ConstantExpr::getNeg(DivRHS)); + // 0 - (C << X) -> (-C << X) + if (Op1I->getOpcode() == Instruction::Shl) + if (ConstantInt *CSI = dyn_cast<ConstantInt>(Op0)) + if (CSI->isZero()) + if (Value *ShlLHSNeg = dyn_castNegVal(Op1I->getOperand(0))) + return BinaryOperator::CreateShl(ShlLHSNeg, Op1I->getOperand(1)); + // X - X*C --> X * (1-C) ConstantInt *C2 = 0; if (dyn_castFoldableMul(Op1I, C2) == Op0) { |