From b6404a8ca6e7d3a77894f3dcfdad89cda1eb6042 Mon Sep 17 00:00:00 2001 From: Sanjay Patel Date: Wed, 6 Dec 2017 21:22:57 +0000 Subject: [InstCombine] canonicalize constant-minus-boolean to select-of-constants This restores the half of: https://reviews.llvm.org/rL75531 that was reverted at: https://reviews.llvm.org/rL159230 For the x86 case mentioned there, we now produce: leal 1(%rdi), %eax subl %esi, %eax We have target hooks to invert this in DAGCombiner (and x86 is enabled) with: https://reviews.llvm.org/rL296977 https://reviews.llvm.org/rL311731 AArch64 and possibly other targets would probably benefit from enabling those hooks too. See PR30327: https://bugs.llvm.org/show_bug.cgi?id=30327#c2 Differential Revision: https://reviews.llvm.org/D40612 llvm-svn: 319964 --- llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) (limited to 'llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp') diff --git a/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp b/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp index d28d615f47e..68889764484 100644 --- a/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp +++ b/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp @@ -1520,8 +1520,13 @@ Instruction *InstCombiner::visitSub(BinaryOperator &I) { return BinaryOperator::CreateNot(Op1); if (Constant *C = dyn_cast(Op0)) { + Value *X; + // C - zext(bool) -> bool ? C - 1 : C + if (match(Op1, m_ZExt(m_Value(X))) && + X->getType()->getScalarSizeInBits() == 1) + return SelectInst::Create(X, SubOne(C), C); + // C - ~X == X + (1+C) - Value *X = nullptr; if (match(Op1, m_Not(m_Value(X)))) return BinaryOperator::CreateAdd(X, AddOne(C)); -- cgit v1.2.3