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ObjectSizeOffsetEvaluator: Don't run into infinite recursion if we have a cyclic GEP. 

Those can occur in dead code. PR17402.

llvm-svn: 191644
This commit is contained in:
Benjamin Kramer 2013-09-29 19:39:13 +00:00
parent 8814430539
commit 155c9d5d97
2 changed files with 24 additions and 5 deletions
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12
llvm/lib/Analysis/MemoryBuiltins.cpp
View File

@ -634,13 +634,15 @@ SizeOffsetEvalType ObjectSizeOffsetEvaluator::compute_(Value *V) {
if (Instruction *I = dyn_cast<Instruction>(V))
Builder.SetInsertPoint(I);
// record the pointers that were handled in this run, so that they can be
// cleaned later if something fails
SeenVals.insert(V);
// now compute the size and offset
SizeOffsetEvalType Result;
if (GEPOperator *GEP = dyn_cast<GEPOperator>(V)) {
// Record the pointers that were handled in this run, so that they can be
// cleaned later if something fails. We also use this set to break cycles that
// can occur in dead code.
if (!SeenVals.insert(V)) {
Result = unknown();
} else if (GEPOperator *GEP = dyn_cast<GEPOperator>(V)) {
Result = visitGEPOperator(*GEP);
} else if (Instruction *I = dyn_cast<Instruction>(V)) {
Result = visit(*I);

17
llvm/test/Instrumentation/BoundsChecking/simple.ll
View File

@ -126,3 +126,20 @@ define i64 @f12(i64 %x, i64 %y) nounwind {
%4 = load i64* %3, align 8
ret i64 %4
}
; PR17402
; CHECK-LABEL: @f13
define void @f13() nounwind {
entry:
br label %alive
dead:
; Self-refential GEPs can occur in dead code.
%incdec.ptr = getelementptr inbounds i32* %incdec.ptr, i64 1
; CHECK: %incdec.ptr = getelementptr inbounds i32* %incdec.ptr
%l = load i32* %incdec.ptr
br label %alive
alive:
ret void
}