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[InstCombine] remove fold of an icmp pattern that should never happen

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While removing a scalar shackle from an icmp fold, I noticed that I couldn't find any tests to trigger
this code path.

The 'and' shrinking transform should be handled by InstCombiner::foldCastedBitwiseLogic()
or eliminated with InstSimplify. The icmp narrowing is part of InstCombiner::foldICmpWithCastAndCast().

Differential Revision: https://reviews.llvm.org/D24031 

llvm-svn: 280370
This commit is contained in:
Sanjay Patel 2016-09-01 14:20:43 +00:00
parent b66a4a20b1
commit e65f7b0df0
2 changed files with 15 additions and 15 deletions
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15
lib/Transforms/InstCombine/InstCombineCompares.cpp
View File

@ -1526,21 +1526,6 @@ Instruction *InstCombiner::foldICmpAndConstConst(ICmpInst &Cmp,
}
}
// If the LHS is an AND of a zext, and we have an equality compare, we can
// shrink the and/compare to the smaller type, eliminating the cast.
if (ZExtInst *Cast = dyn_cast<ZExtInst>(And->getOperand(0))) {
IntegerType *Ty = cast<IntegerType>(Cast->getSrcTy());
// Make sure we don't compare the upper bits, SimplifyDemandedBits
// should fold the icmp to true/false in that case.
if (Cmp.isEquality() && C1->getActiveBits() <= Ty->getBitWidth()) {
Value *NewAnd = Builder->CreateAnd(Cast->getOperand(0),
ConstantExpr::getTrunc(C2, Ty));
NewAnd->takeName(And);
return new ICmpInst(Cmp.getPredicate(), NewAnd,
ConstantExpr::getTrunc(RHS, Ty));
}
}
if (Instruction *I = foldICmpAndShift(Cmp, And, C1))
return I;

15
test/Transforms/InstCombine/cast.ll
View File

@ -371,6 +371,21 @@ define <2 x i1> @test31vec(<2 x i64> %A) {
ret <2 x i1> %D
}
; Verify that the 'and' was narrowed, the zext was eliminated, and the compare was narrowed
; even for vectors. Earlier folds should ensure that the icmp(and(zext)) pattern never occurs.
define <2 x i1> @test32vec(<2 x i8> %A) {
; CHECK-LABEL: @test32vec(
; CHECK-NEXT: [[TMP1:%.*]] = and <2 x i8> %A, <i8 42, i8 42>
; CHECK-NEXT: [[D:%.*]] = icmp eq <2 x i8> [[TMP1]], <i8 10, i8 10>
; CHECK-NEXT: ret <2 x i1> [[D]]
;
%B = zext <2 x i8> %A to <2 x i16>
%C = and <2 x i16> %B, <i16 42, i16 42>
%D = icmp eq <2 x i16> %C, <i16 10, i16 10>
ret <2 x i1> %D
}
define i32 @test33(i32 %c1) {
; CHECK-LABEL: @test33(
; CHECK-NEXT: ret i32 %c1