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Fix PR8161, in which an unreachable loop causes recursive instruction simplification to try 

to replace an instruction with itself.  Add a predicate to the simplifier to prevent this case.

llvm-svn: 114097
This commit is contained in:
Owen Anderson 2010-09-16 17:42:36 +00:00
parent ee1934a2da
commit 94532cb297
2 changed files with 44 additions and 11 deletions
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35
llvm/lib/Analysis/InstructionSimplify.cpp
View File

@ -423,31 +423,44 @@ Value *llvm::SimplifyCmpInst(unsigned Predicate, Value *LHS, Value *RHS,
/// SimplifyInstruction - See if we can compute a simplified version of this
/// instruction. If not, this returns null.
Value *llvm::SimplifyInstruction(Instruction *I, const TargetData *TD) {
Value *Ret = 0;
switch (I->getOpcode()) {
default:
return ConstantFoldInstruction(I, TD);
case Instruction::Add:
return SimplifyAddInst(I->getOperand(0), I->getOperand(1),
cast<BinaryOperator>(I)->hasNoSignedWrap(),
cast<BinaryOperator>(I)->hasNoUnsignedWrap(), TD);
Ret = SimplifyAddInst(I->getOperand(0), I->getOperand(1),
cast<BinaryOperator>(I)->hasNoSignedWrap(),
cast<BinaryOperator>(I)->hasNoUnsignedWrap(), TD);
break;
case Instruction::And:
return SimplifyAndInst(I->getOperand(0), I->getOperand(1), TD);
Ret = SimplifyAndInst(I->getOperand(0), I->getOperand(1), TD);
break;
case Instruction::Or:
return SimplifyOrInst(I->getOperand(0), I->getOperand(1), TD);
Ret = SimplifyOrInst(I->getOperand(0), I->getOperand(1), TD);
break;
case Instruction::ICmp:
return SimplifyICmpInst(cast<ICmpInst>(I)->getPredicate(),
I->getOperand(0), I->getOperand(1), TD);
Ret = SimplifyICmpInst(cast<ICmpInst>(I)->getPredicate(),
I->getOperand(0), I->getOperand(1), TD);
break;
case Instruction::FCmp:
return SimplifyFCmpInst(cast<FCmpInst>(I)->getPredicate(),
I->getOperand(0), I->getOperand(1), TD);
Ret = SimplifyFCmpInst(cast<FCmpInst>(I)->getPredicate(),
I->getOperand(0), I->getOperand(1), TD);
break;
case Instruction::Select:
return SimplifySelectInst(I->getOperand(0), I->getOperand(1),
Ret = SimplifySelectInst(I->getOperand(0), I->getOperand(1),
I->getOperand(2), TD);
break;
case Instruction::GetElementPtr: {
SmallVector<Value*, 8> Ops(I->op_begin(), I->op_end());
return SimplifyGEPInst(&Ops[0], Ops.size(), TD);
Ret = SimplifyGEPInst(&Ops[0], Ops.size(), TD);
break;
}
}
// It is possible, in situations involving unreachable loops, to
// have a replacement that, through recursive simplification, ends up
// simplifying to itself.
return Ret != I ? Ret : 0;
}
/// ReplaceAndSimplifyAllUses - Perform From->replaceAllUsesWith(To) and then

20
llvm/test/Transforms/CorrelatedValuePropagation/crash.ll Normal file
View File

@ -0,0 +1,20 @@
; RUN: opt < %s -correlated-propagation
; PR8161
define void @test1() nounwind ssp {
entry:
br label %for.end
for.cond.us.us: ; preds = %for.cond.us.us
%cmp6.i.us.us = icmp sgt i32 1, 0
%lor.ext.i.us.us = zext i1 %cmp6.i.us.us to i32
%lor.ext.add.i.us.us = select i1 %cmp6.i.us.us, i32 %lor.ext.i.us.us, i32 undef
%conv.i.us.us = trunc i32 %lor.ext.add.i.us.us to i16
%sext.us.us = shl i16 %conv.i.us.us, 8
%conv6.us.us = ashr i16 %sext.us.us, 8
%and.us.us = and i16 %conv6.us.us, %and.us.us
br i1 false, label %for.end, label %for.cond.us.us
for.end: ; preds = %for.cond.us, %for.cond.us.us, %entry
ret void
}