From 2291a38a78381e92fbe8e6b93c980eba45c845f7 Mon Sep 17 00:00:00 2001 From: David Majnemer Date: Mon, 1 Feb 2016 17:37:56 +0000 Subject: [PATCH] [InstCombine] Don't transform (X+INT_MAX)>=(Y+INT_MAX) -> (X<=Y) This miscompile came about because we tried to use a transform which was only appropriate for xor operators when addition was present. This fixes PR26407. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@259375 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/Transforms/InstCombine/InstCombineCompares.cpp | 2 +- test/Transforms/InstCombine/icmp.ll | 12 ++++++++++++ 2 files changed, 13 insertions(+), 1 deletion(-) diff --git a/lib/Transforms/InstCombine/InstCombineCompares.cpp b/lib/Transforms/InstCombine/InstCombineCompares.cpp index f322e4ed7aa..051fd1084f7 100644 --- a/lib/Transforms/InstCombine/InstCombineCompares.cpp +++ b/lib/Transforms/InstCombine/InstCombineCompares.cpp @@ -3877,7 +3877,7 @@ Instruction *InstCombiner::visitICmpInst(ICmpInst &I) { BO1->getOperand(0)); } - if (CI->isMaxValue(true)) { + if (BO0->getOpcode() == Instruction::Xor && CI->isMaxValue(true)) { ICmpInst::Predicate Pred = I.isSigned() ? I.getUnsignedPredicate() : I.getSignedPredicate(); diff --git a/test/Transforms/InstCombine/icmp.ll b/test/Transforms/InstCombine/icmp.ll index 7d6ec96b532..1e64cd7f582 100644 --- a/test/Transforms/InstCombine/icmp.ll +++ b/test/Transforms/InstCombine/icmp.ll @@ -1672,3 +1672,15 @@ define i1 @cmp_slt_rhs_inc(float %x, i32 %i) { %cmp = icmp slt i32 %conv, %inc ret i1 %cmp } + +; CHECK-LABEL: @PR26407 +; CHECK-NEXT: %[[addx:.*]] = add i32 %x, 2147483647 +; CHECK-NEXT: %[[addy:.*]] = add i32 %y, 2147483647 +; CHECK-NEXT: %[[cmp:.*]] = icmp uge i32 %[[addx]], %[[addy]] +; CHECK-NEXT: ret i1 %[[cmp]] +define i1 @PR26407(i32 %x, i32 %y) { + %addx = add i32 %x, 2147483647 + %addy = add i32 %y, 2147483647 + %cmp = icmp uge i32 %addx, %addy + ret i1 %cmp +} -- 2.11.0