From b1b7a2f7b63db915fbc0e7ee5e1811b8846fbd9b Mon Sep 17 00:00:00 2001 From: Nikita Popov Date: Sun, 20 Oct 2019 20:19:42 +0000 Subject: [InstCombine] Fold uadd.sat(a, b) == 0 and usub.sat(a, b) == 0 This adds folds for comparing uadd.sat/usub.sat with zero: * uadd.sat(a, b) == 0 => a == 0 && b == 0 => (a | b) == 0 * usub.sat(a, b) == 0 => a <= b And inverted forms for !=. Differential Revision: https://reviews.llvm.org/D69224 llvm-svn: 375374 --- .../Transforms/InstCombine/InstCombineCompares.cpp | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+) (limited to 'llvm/lib') diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp index 601295339ad..a9f64feb600 100644 --- a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp +++ b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp @@ -3076,6 +3076,28 @@ Instruction *InstCombiner::foldICmpEqIntrinsicWithConstant(ICmpInst &Cmp, } break; } + + case Intrinsic::uadd_sat: { + // uadd.sat(a, b) == 0 -> (a | b) == 0 + if (C.isNullValue()) { + Value *Or = Builder.CreateOr(II->getArgOperand(0), II->getArgOperand(1)); + return replaceInstUsesWith(Cmp, Builder.CreateICmp( + Cmp.getPredicate(), Or, Constant::getNullValue(Ty))); + + } + break; + } + + case Intrinsic::usub_sat: { + // usub.sat(a, b) == 0 -> a <= b + if (C.isNullValue()) { + ICmpInst::Predicate NewPred = Cmp.getPredicate() == ICmpInst::ICMP_EQ + ? ICmpInst::ICMP_ULE : ICmpInst::ICMP_UGT; + return ICmpInst::Create(Instruction::ICmp, NewPred, + II->getArgOperand(0), II->getArgOperand(1)); + } + break; + } default: break; } -- cgit v1.2.3