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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 | 37a8197b6174e5e7d3597e93e4f3cdf119485d15 (patch) | |
| tree | 66c155540ab0909b28a05b0fb2c78ac50eebbb48 /llvm/lib/Transforms | |
| parent | 9aeccadce40881bc136e05a5a62e0071f792dc1c (diff) | |
| download | bcm5719-llvm-37a8197b6174e5e7d3597e93e4f3cdf119485d15.tar.gz bcm5719-llvm-37a8197b6174e5e7d3597e93e4f3cdf119485d15.zip | |
Add a small transform: transform -(X<<Y) to (-X<<Y) when the shift has a single
use and X is free to negate.
llvm-svn: 94941
Diffstat (limited to 'llvm/lib/Transforms')
| -rw-r--r-- | llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp b/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp index 4891ff00e7b..119b1cad632 100644 --- a/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp +++ b/llvm/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) { |
