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[InstSimplify] restrict icmp fold with 2 sdiv exact operands (PR32949)

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These folds were introduced with https://reviews.llvm.org/rL127064 as part of solving:
https://bugs.llvm.org/show_bug.cgi?id=9343

As shown here:
http://rise4fun.com/Alive/C8
...however, the sdiv exact case needs a stronger predicate.

I opted for duplicated code instead of adding another fallthrough because I think that's 
easier to read (and edit in case we need/want to restrict/loosen the predicates any more).

This should fix:
https://bugs.llvm.org/show_bug.cgi?id=32949
https://bugs.llvm.org/show_bug.cgi?id=32948

Differential Revision: https://reviews.llvm.org/D32954

llvm-svn: 303104
This commit is contained in:
Sanjay Patel 2017-05-15 19:16:49 +00:00
parent d11ab9e578
commit 6116bcb0ac
2 changed files with 16 additions and 4 deletions
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13
lib/Analysis/InstructionSimplify.cpp
View File

@ -2827,10 +2827,19 @@ static Value *simplifyICmpWithBinOp(CmpInst::Predicate Pred, Value *LHS,
break;
case Instruction::UDiv:
case Instruction::LShr:
if (ICmpInst::isSigned(Pred))
if (ICmpInst::isSigned(Pred) || !LBO->isExact() || !RBO->isExact())
break;
LLVM_FALLTHROUGH;
if (Value *V = SimplifyICmpInst(Pred, LBO->getOperand(0),
RBO->getOperand(0), Q, MaxRecurse - 1))
return V;
break;
case Instruction::SDiv:
if (!ICmpInst::isEquality(Pred) || !LBO->isExact() || !RBO->isExact())
break;
if (Value *V = SimplifyICmpInst(Pred, LBO->getOperand(0),
RBO->getOperand(0), Q, MaxRecurse - 1))
return V;
break;
case Instruction::AShr:
if (!LBO->isExact() || !RBO->isExact())
break;

7
test/Transforms/InstSimplify/compare.ll
View File

@ -598,11 +598,14 @@ define i1 @sdiv_exact_equality(i32 %Z) {
ret i1 %C
}
; FIXME: But not other preds: PR32949 - https://bugs.llvm.org/show_bug.cgi?id=32949
; But not other preds: PR32949 - https://bugs.llvm.org/show_bug.cgi?id=32949
define i1 @sdiv_exact_not_equality(i32 %Z) {
; CHECK-LABEL: @sdiv_exact_not_equality(
; CHECK-NEXT: ret i1 true
; CHECK-NEXT: [[A:%.*]] = sdiv exact i32 10, %Z
; CHECK-NEXT: [[B:%.*]] = sdiv exact i32 20, %Z
; CHECK-NEXT: [[C:%.*]] = icmp ult i32 [[A]], [[B]]
; CHECK-NEXT: ret i1 [[C]]
;
%A = sdiv exact i32 10, %Z
%B = sdiv exact i32 20, %Z