From 319be53a1fa5b4ec487cc726c35fe9937c61f8c3 Mon Sep 17 00:00:00 2001 From: Evan Cheng Date: Tue, 26 Jun 2012 22:03:13 +0000 Subject: Remove a instcombine transform that (no longer?) makes sense: // C - zext(bool) -> bool ? C - 1 : C if (ZExtInst *ZI = dyn_cast(Op1)) if (ZI->getSrcTy()->isIntegerTy(1)) return SelectInst::Create(ZI->getOperand(0), SubOne(C), C); This ends up forming sext i1 instructions that codegen to terrible code. e.g. int blah(_Bool x, _Bool y) { return (x - y) + 1; } => movzbl %dil, %eax movzbl %sil, %ecx shll $31, %ecx sarl $31, %ecx leal 1(%rax,%rcx), %eax ret Without the rule, llvm now generates: movzbl %sil, %ecx movzbl %dil, %eax incl %eax subl %ecx, %eax ret It also helps with ARM (and pretty much any target that doesn't have a sext i1 :-). The transformation was done as part of Eli's r75531. He has given the ok to remove it. rdar://11748024 llvm-svn: 159230 --- llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp | 5 ----- 1 file changed, 5 deletions(-) (limited to 'llvm/lib') diff --git a/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp b/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp index 00f99741259..99b62f8d05a 100644 --- a/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp +++ b/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp @@ -544,11 +544,6 @@ Instruction *InstCombiner::visitSub(BinaryOperator &I) { if (Instruction *R = FoldOpIntoSelect(I, SI)) return R; - // C - zext(bool) -> bool ? C - 1 : C - if (ZExtInst *ZI = dyn_cast(Op1)) - if (ZI->getSrcTy()->isIntegerTy(1)) - return SelectInst::Create(ZI->getOperand(0), SubOne(C), C); - // C-(X+C2) --> (C-C2)-X ConstantInt *C2; if (match(Op1, m_Add(m_Value(X), m_ConstantInt(C2)))) -- cgit v1.2.3