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Fix incorrect partial aliasing

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Update testcases

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@227099 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Daniel Berlin
2015-01-26 17:31:17 +00:00
parent 0d16cafbe3
commit 8e43882572
4 changed files with 49 additions and 17 deletions
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27
lib/Analysis/CFLAliasAnalysis.cpp
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@@ -298,8 +298,11 @@ public:
}
void visitSelectInst(SelectInst &Inst) {
auto *Condition = Inst.getCondition();
Output.push_back(Edge(&Inst, Condition, EdgeType::Assign, AttrNone));
// Condition is not processed here (The actual statement producing
// the condition result is processed elsewhere). For select, the
// condition is evaluated, but not loaded, stored, or assigned
// simply as a result of being the condition of a select.
auto *TrueVal = Inst.getTrueValue();
Output.push_back(Edge(&Inst, TrueVal, EdgeType::Assign, AttrNone));
auto *FalseVal = Inst.getFalseValue();
@@ -771,7 +774,10 @@ static Optional<StratifiedAttr> valueToAttrIndex(Value *Val) {
return AttrGlobalIndex;
if (auto *Arg = dyn_cast<Argument>(Val))
if (!Arg->hasNoAliasAttr())
// Only pointer arguments should have the argument attribute,
// because things can't escape through scalars without us seeing a
// cast, and thus, interaction with them doesn't matter.
if (!Arg->hasNoAliasAttr() && Arg->getType()->isPointerTy())
return argNumberToAttrIndex(Arg->getArgNo());
return NoneType();
}
@@ -994,10 +1000,6 @@ CFLAliasAnalysis::query(const AliasAnalysis::Location &LocA,
auto SetA = *MaybeA;
auto SetB = *MaybeB;
if (SetA.Index == SetB.Index)
return AliasAnalysis::PartialAlias;
auto AttrsA = Sets.getLink(SetA.Index).Attrs;
auto AttrsB = Sets.getLink(SetB.Index).Attrs;
// Stratified set attributes are used as markets to signify whether a member
@@ -1012,5 +1014,16 @@ CFLAliasAnalysis::query(const AliasAnalysis::Location &LocA,
if (AttrsA.any() && AttrsB.any())
return AliasAnalysis::MayAlias;
// We currently unify things even if the accesses to them may not be in
// bounds, so we can't return partial alias here because we don't
// know whether the pointer is really within the object or not.
// IE Given an out of bounds GEP and an alloca'd pointer, we may
// unify the two. We can't return partial alias for this case.
// Since we do not currently track enough information to
// differentiate
if (SetA.Index == SetB.Index)
return AliasAnalysis::MayAlias;
return AliasAnalysis::NoAlias;
}