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[InstCombine] Don't transform (X+INT_MAX)>=(Y+INT_MAX) -> (X<=Y)

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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
This commit is contained in:
David Majnemer 2016-02-01 17:37:56 +00:00
parent d9e550023c
commit 2291a38a78
2 changed files with 13 additions and 1 deletions
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2
lib/Transforms/InstCombine/InstCombineCompares.cpp
View File

@ -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();

12
test/Transforms/InstCombine/icmp.ll
View File

@ -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
}