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Extend the AliasAnalysis::pointsToConstantMemory interface to allow it

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to optionally look for constant or local (alloca) memory.

Teach BasicAliasAnalysis::pointsToConstantMemory to look through Select
and Phi nodes, and to support looking for local memory.

Remove FunctionAttrs' PointsToLocalOrConstantMemory function, now that
AliasAnalysis knows all the tricks that it knew.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@118412 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dan Gohman
2010-11-08 16:45:26 +00:00
parent c80cbf2540
commit a25e5dbcc2
9 changed files with 85 additions and 83 deletions
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65
lib/Analysis/BasicAliasAnalysis.cpp
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@@ -456,7 +456,7 @@ namespace {
/// pointsToConstantMemory - Chase pointers until we find a (constant
/// global) or not.
virtual bool pointsToConstantMemory(const Location &Loc);
virtual bool pointsToConstantMemory(const Location &Loc, bool OrLocal);
/// getModRefBehavior - Return the behavior when calling the given
/// call site.
@@ -517,18 +517,61 @@ ImmutablePass *llvm::createBasicAliasAnalysisPass() {
return new BasicAliasAnalysis();
}
/// pointsToConstantMemory - Returns whether the given pointer value
/// points to memory that is local to the function, with global constants being
/// considered local to all functions.
bool
BasicAliasAnalysis::pointsToConstantMemory(const Location &Loc, bool OrLocal) {
assert(Visited.empty() && "Visited must be cleared after use!");
/// pointsToConstantMemory - Chase pointers until we find a (constant
/// global) or not.
bool BasicAliasAnalysis::pointsToConstantMemory(const Location &Loc) {
if (const GlobalVariable *GV =
dyn_cast<GlobalVariable>(Loc.Ptr->getUnderlyingObject()))
// Note: this doesn't require GV to be "ODR" because it isn't legal for a
// global to be marked constant in some modules and non-constant in others.
// GV may even be a declaration, not a definition.
return GV->isConstant();
SmallVector<const Value *, 16> Worklist;
Worklist.push_back(Loc.Ptr);
do {
const Value *V = Worklist.pop_back_val()->getUnderlyingObject();
if (!Visited.insert(V)) {
Visited.clear();
return AliasAnalysis::pointsToConstantMemory(Loc, OrLocal);
}
return AliasAnalysis::pointsToConstantMemory(Loc);
// An alloca instruction defines local memory.
if (OrLocal && isa<AllocaInst>(V))
continue;
// A global constant counts as local memory for our purposes.
if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(V)) {
// Note: this doesn't require GV to be "ODR" because it isn't legal for a
// global to be marked constant in some modules and non-constant in
// others. GV may even be a declaration, not a definition.
if (!GV->isConstant()) {
Visited.clear();
return AliasAnalysis::pointsToConstantMemory(Loc, OrLocal);
}
continue;
}
// If both select values point to local memory, then so does the select.
if (const SelectInst *SI = dyn_cast<SelectInst>(V)) {
Worklist.push_back(SI->getTrueValue());
Worklist.push_back(SI->getFalseValue());
continue;
}
// If all values incoming to a phi node point to local memory, then so does
// the phi.
if (const PHINode *PN = dyn_cast<PHINode>(V)) {
for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
Worklist.push_back(PN->getIncomingValue(i));
continue;
}
// Otherwise be conservative.
Visited.clear();
return AliasAnalysis::pointsToConstantMemory(Loc, OrLocal);
} while (!Worklist.empty());
Visited.clear();
return true;
}
/// getModRefBehavior - Return the behavior when calling the given call site.