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[InstCombine] add another test for wrong icmp constant (PR27792) 

It doesn't matter if the comparison is unsigned; the inc/dec is always signed.

llvm-svn: 269831
This commit is contained in:
Sanjay Patel 2016-05-17 20:20:40 +00:00
parent 12de0b91ac
commit 22b01febd4
2 changed files with 11 additions and 2 deletions
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2
llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
View File

@ -3150,7 +3150,7 @@ static ICmpInst *canonicalizeCmpWithConstant(ICmpInst &I) {
// Increment or decrement the constant and set the new comparison predicate:
// ULE -> ULT ; UGE -> UGT ; SLE -> SLT ; SGE -> SGT
Constant *OneOrNegOne = ConstantInt::get(Op1Type, IsLE ? 1 : -1, IsSigned);
Constant *OneOrNegOne = ConstantInt::get(Op1Type, IsLE ? 1 : -1, true);
CmpInst::Predicate NewPred = IsLE ? ICmpInst::ICMP_ULT: ICmpInst::ICMP_UGT;
NewPred = IsSigned ? ICmpInst::getSignedPredicate(NewPred) : NewPred;
return new ICmpInst(NewPred, Op0, ConstantExpr::getAdd(Op1C, OneOrNegOne));

11
llvm/test/Transforms/InstCombine/icmp.ll
View File

@ -2098,7 +2098,7 @@ return: ; preds = %if.end, %entry, %if
ret void
}
; When canonicalizing to 'sgt', make sure the constant is correct.
; When canonicalizing to 'gt/lt', make sure the constant is correct.
define i1 @PR27792(i128 %a) {
; CHECK-LABEL: @PR27792(
@ -2109,3 +2109,12 @@ define i1 @PR27792(i128 %a) {
ret i1 %cmp
}
define i1 @PR27792_2(i128 %a) {
; CHECK-LABEL: @PR27792_2(
; CHECK-NEXT: [[B:%.*]] = icmp ne i128 %a, 0
; CHECK-NEXT: ret i1 [[B]]
;
%b = icmp uge i128 %a, 1
ret i1 %b
}