From e880187bb66294944e68c1d5e099813adb4b55e2 Mon Sep 17 00:00:00 2001 From: David Majnemer Date: Thu, 15 May 2014 00:02:20 +0000 Subject: [PATCH] InstCombine: Optimize -x s< cst Summary: This gets rid of a sub instruction by moving the negation to the constant when valid. Reviewers: nicholas Subscribers: llvm-commits Differential Revision: http://reviews.llvm.org/D3773 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@208827 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/Transforms/InstCombine/InstCombineCompares.cpp | 10 ++++++++++ test/Transforms/InstCombine/icmp.ll | 9 +++++++++ 2 files changed, 19 insertions(+) diff --git a/lib/Transforms/InstCombine/InstCombineCompares.cpp b/lib/Transforms/InstCombine/InstCombineCompares.cpp index 9424ad2b853..02e8bf10135 100644 --- a/lib/Transforms/InstCombine/InstCombineCompares.cpp +++ b/lib/Transforms/InstCombine/InstCombineCompares.cpp @@ -2971,6 +2971,16 @@ Instruction *InstCombiner::visitICmpInst(ICmpInst &I) { BO0->hasOneUse() && BO1->hasOneUse()) return new ICmpInst(Pred, D, B); + // icmp (0-X) < cst --> x > -cst + if (NoOp0WrapProblem && ICmpInst::isSigned(Pred)) { + Value *X; + if (match(BO0, m_Neg(m_Value(X)))) + if (ConstantInt *RHSC = dyn_cast(Op1)) + if (!RHSC->isMinValue(/*isSigned=*/true)) + return new ICmpInst(I.getSwappedPredicate(), X, + ConstantExpr::getNeg(RHSC)); + } + BinaryOperator *SRem = nullptr; // icmp (srem X, Y), Y if (BO0 && BO0->getOpcode() == Instruction::SRem && diff --git a/test/Transforms/InstCombine/icmp.ll b/test/Transforms/InstCombine/icmp.ll index 12a4744cc0f..f45897cd3ee 100644 --- a/test/Transforms/InstCombine/icmp.ll +++ b/test/Transforms/InstCombine/icmp.ll @@ -1356,3 +1356,12 @@ define i1 @icmp_ashr_ashr_ne(i32 %a, i32 %b) nounwind { %z = icmp ne i32 %x, %y ret i1 %z } + +; CHECK-LABEL: @icmp_neg_cst_slt +; CHECK-NEXT: [[CMP:%[a-z0-9]+]] = icmp sgt i32 %a, 10 +; CHECK-NEXT: ret i1 [[CMP]] +define i1 @icmp_neg_cst_slt(i32 %a) { + %1 = sub nsw i32 0, %a + %2 = icmp slt i32 %1, -10 + ret i1 %2 +}