diff options
| -rw-r--r-- | lib/Transforms/InstCombine/InstCombineAddSub.cpp | 7 | ||||
| -rw-r--r-- | test/Transforms/InstCombine/sub.ll | 8 |
2 files changed, 15 insertions, 0 deletions
diff --git a/lib/Transforms/InstCombine/InstCombineAddSub.cpp b/lib/Transforms/InstCombine/InstCombineAddSub.cpp index 4891ff00e7..119b1cad63 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) { diff --git a/test/Transforms/InstCombine/sub.ll b/test/Transforms/InstCombine/sub.ll index fa0322a44e..29bd7be2ff 100644 --- a/test/Transforms/InstCombine/sub.ll +++ b/test/Transforms/InstCombine/sub.ll @@ -272,4 +272,12 @@ define i64 @test25(i8* %P, i64 %A){ ; CHECK-NEXT: ret i64 } +define i32 @test26(i32 %x) { + %shl = shl i32 3, %x + %neg = sub i32 0, %shl + ret i32 %neg +; CHECK: @test26 +; CHECK-NEXT: shl i32 -3 +; CHECK-NEXT: ret i32 +} |