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fix PR12075, a regression in a recent transform I added. In unreachable code, gep chains can be infinite. Just like "stripPointerCasts", use a set to keep track of visited instructions so we don't recurse infinitely.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@151383 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2012-02-24 19:01:58 +00:00
parent 1a2d061ec0
commit 009e2650d6
2 changed files with 29 additions and 5 deletions
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24
lib/Analysis/InstructionSimplify.cpp
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@ -1522,13 +1522,27 @@ static Value *ExtractEquivalentCondition(Value *V, CmpInst::Predicate Pred,
/// stripPointerAdjustments - This is like Value::stripPointerCasts, but also /// stripPointerAdjustments - This is like Value::stripPointerCasts, but also
/// removes inbounds gep operations, regardless of their indices. /// removes inbounds gep operations, regardless of their indices.
static Value *stripPointerAdjustments(Value *V) { static Value *stripPointerAdjustmentsImpl(Value *V,
if (GEPOperator *GEP = dyn_cast<GEPOperator>(V)) SmallPtrSet<GEPOperator*, 8> &VisitedGEPs) {
if (GEP->isInBounds()) GEPOperator *GEP = dyn_cast<GEPOperator>(V);
return stripPointerAdjustments(GEP->getOperand(0)->stripPointerCasts()); if (GEP == 0 || !GEP->isInBounds())
return V; return V;
// If we've already seen this GEP, we will end up infinitely looping. This
// can happen in unreachable code.
if (!VisitedGEPs.insert(GEP))
return V;
return stripPointerAdjustmentsImpl(GEP->getOperand(0)->stripPointerCasts(),
VisitedGEPs);
} }
static Value *stripPointerAdjustments(Value *V) {
SmallPtrSet<GEPOperator*, 8> VisitedGEPs;
return stripPointerAdjustmentsImpl(V, VisitedGEPs);
}
/// SimplifyICmpInst - Given operands for an ICmpInst, see if we can /// SimplifyICmpInst - Given operands for an ICmpInst, see if we can
/// fold the result. If not, this returns null. /// fold the result. If not, this returns null.
static Value *SimplifyICmpInst(unsigned Predicate, Value *LHS, Value *RHS, static Value *SimplifyICmpInst(unsigned Predicate, Value *LHS, Value *RHS,

10
test/Transforms/InstSimplify/compare.ll
View File

@ -463,3 +463,13 @@ define i1 @alloca_compare(i64 %idx) {
; CHECK: alloca_compare ; CHECK: alloca_compare
; CHECK: ret i1 false ; CHECK: ret i1 false
} }
; PR12075
define i1 @infinite_gep() {
ret i1 1
unreachableblock:
%X = getelementptr i32 *%X, i32 1
%Y = icmp eq i32* %X, null
ret i1 %Y
}