#include "llvm/Function.h"
#include "llvm/LLVMContext.h"
#include "llvm/Analysis/AliasAnalysis.h"
+#include "llvm/Analysis/CaptureTracking.h"
#include "llvm/Analysis/Dominators.h"
#include "llvm/Analysis/InstructionSimplify.h"
#include "llvm/Analysis/MemoryBuiltins.h"
bool MemoryDependenceAnalysis::runOnFunction(Function &) {
AA = &getAnalysis<AliasAnalysis>();
TD = getAnalysisIfAvailable<TargetData>();
+ DT = getAnalysisIfAvailable<DominatorTree>();
if (PredCache == 0)
PredCache.reset(new PredIteratorCache());
return false;
AliasAnalysis::Location &Loc,
AliasAnalysis *AA) {
if (const LoadInst *LI = dyn_cast<LoadInst>(Inst)) {
- if (LI->isVolatile()) {
- Loc = AliasAnalysis::Location();
+ if (LI->isUnordered()) {
+ Loc = AA->getLocation(LI);
+ return AliasAnalysis::Ref;
+ } else if (LI->getOrdering() == Monotonic) {
+ Loc = AA->getLocation(LI);
return AliasAnalysis::ModRef;
}
- Loc = AA->getLocation(LI);
- return AliasAnalysis::Ref;
+ Loc = AliasAnalysis::Location();
+ return AliasAnalysis::ModRef;
}
if (const StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
- if (SI->isVolatile()) {
- Loc = AliasAnalysis::Location();
+ if (SI->isUnordered()) {
+ Loc = AA->getLocation(SI);
+ return AliasAnalysis::Mod;
+ } else if (SI->getOrdering() == Monotonic) {
+ Loc = AA->getLocation(SI);
return AliasAnalysis::ModRef;
}
- Loc = AA->getLocation(SI);
- return AliasAnalysis::Mod;
+ Loc = AliasAnalysis::Location();
+ return AliasAnalysis::ModRef;
}
if (const VAArgInst *V = dyn_cast<VAArgInst>(Inst)) {
// unknown, otherwise it is non-local.
if (BB != &BB->getParent()->getEntryBlock())
return MemDepResult::getNonLocal();
- return MemDepResult::getUnknown();
+ return MemDepResult::getNonFuncLocal();
}
/// isLoadLoadClobberIfExtendedToFullWidth - Return true if LI is a load that
getLoadLoadClobberFullWidthSize(const Value *MemLocBase, int64_t MemLocOffs,
unsigned MemLocSize, const LoadInst *LI,
const TargetData &TD) {
- // We can only extend non-volatile integer loads.
- if (!isa<IntegerType>(LI->getType()) || LI->isVolatile()) return 0;
+ // We can only extend simple integer loads.
+ if (!isa<IntegerType>(LI->getType()) || !LI->isSimple()) return 0;
// Get the base of this load.
int64_t LIOffs = 0;
!TD.fitsInLegalInteger(NewLoadByteSize*8))
return 0;
+ if (LIOffs+NewLoadByteSize > MemLocEnd &&
+ LI->getParent()->getParent()->hasFnAttr(Attribute::AddressSafety)) {
+ // We will be reading past the location accessed by the original program.
+ // While this is safe in a regular build, Address Safety analysis tools
+ // may start reporting false warnings. So, don't do widening.
+ return 0;
+ }
+
// If a load of this width would include all of MemLoc, then we succeed.
if (LIOffs+NewLoadByteSize >= MemLocEnd)
return NewLoadByteSize;
NewLoadByteSize <<= 1;
}
-
- return 0;
+}
+
+namespace {
+ /// Only find pointer captures which happen before the given instruction. Uses
+ /// the dominator tree to determine whether one instruction is before another.
+ struct CapturesBefore : public CaptureTracker {
+ CapturesBefore(const Instruction *I, DominatorTree *DT)
+ : BeforeHere(I), DT(DT), Captured(false) {}
+
+ void tooManyUses() { Captured = true; }
+
+ bool shouldExplore(Use *U) {
+ Instruction *I = cast<Instruction>(U->getUser());
+ BasicBlock *BB = I->getParent();
+ if (BeforeHere != I &&
+ (!DT->isReachableFromEntry(BB) || DT->dominates(BeforeHere, I)))
+ return false;
+ return true;
+ }
+
+ bool captured(Use *U) {
+ Instruction *I = cast<Instruction>(U->getUser());
+ BasicBlock *BB = I->getParent();
+ if (BeforeHere != I &&
+ (!DT->isReachableFromEntry(BB) || DT->dominates(BeforeHere, I)))
+ return false;
+ Captured = true;
+ return true;
+ }
+
+ const Instruction *BeforeHere;
+ DominatorTree *DT;
+
+ bool Captured;
+ };
+}
+
+AliasAnalysis::ModRefResult
+MemoryDependenceAnalysis::getModRefInfo(const Instruction *Inst,
+ const AliasAnalysis::Location &MemLoc) {
+ AliasAnalysis::ModRefResult MR = AA->getModRefInfo(Inst, MemLoc);
+ if (MR != AliasAnalysis::ModRef) return MR;
+
+ // FIXME: this is really just shoring-up a deficiency in alias analysis.
+ // BasicAA isn't willing to spend linear time determining whether an alloca
+ // was captured before or after this particular call, while we are. However,
+ // with a smarter AA in place, this test is just wasting compile time.
+ if (!DT) return AliasAnalysis::ModRef;
+ const Value *Object = GetUnderlyingObject(MemLoc.Ptr, TD);
+ if (!isIdentifiedObject(Object) || isa<GlobalValue>(Object))
+ return AliasAnalysis::ModRef;
+ ImmutableCallSite CS(Inst);
+ if (!CS.getInstruction()) return AliasAnalysis::ModRef;
+
+ CapturesBefore CB(Inst, DT);
+ llvm::PointerMayBeCaptured(Object, &CB);
+
+ if (isa<Constant>(Object) || CS.getInstruction() == Object || CB.Captured)
+ return AliasAnalysis::ModRef;
+
+ unsigned ArgNo = 0;
+ for (ImmutableCallSite::arg_iterator CI = CS.arg_begin(), CE = CS.arg_end();
+ CI != CE; ++CI, ++ArgNo) {
+ // Only look at the no-capture or byval pointer arguments. If this
+ // pointer were passed to arguments that were neither of these, then it
+ // couldn't be no-capture.
+ if (!(*CI)->getType()->isPointerTy() ||
+ (!CS.doesNotCapture(ArgNo) && !CS.isByValArgument(ArgNo)))
+ continue;
+
+ // If this is a no-capture pointer argument, see if we can tell that it
+ // is impossible to alias the pointer we're checking. If not, we have to
+ // assume that the call could touch the pointer, even though it doesn't
+ // escape.
+ if (!AA->isNoAlias(AliasAnalysis::Location(*CI),
+ AliasAnalysis::Location(Object))) {
+ return AliasAnalysis::ModRef;
+ }
+ }
+ return AliasAnalysis::NoModRef;
}
/// getPointerDependencyFrom - Return the instruction on which a memory
// Values depend on loads if the pointers are must aliased. This means that
// a load depends on another must aliased load from the same value.
if (LoadInst *LI = dyn_cast<LoadInst>(Inst)) {
+ // Atomic loads have complications involved.
+ // FIXME: This is overly conservative.
+ if (!LI->isUnordered())
+ return MemDepResult::getClobber(LI);
+
AliasAnalysis::Location LoadLoc = AA->getLocation(LI);
// If we found a pointer, check if it could be the same as our pointer.
}
if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
+ // Atomic stores have complications involved.
+ // FIXME: This is overly conservative.
+ if (!SI->isUnordered())
+ return MemDepResult::getClobber(SI);
+
// If alias analysis can tell that this store is guaranteed to not modify
// the query pointer, ignore it. Use getModRefInfo to handle cases where
// the query pointer points to constant memory etc.
}
// See if this instruction (e.g. a call or vaarg) mod/ref's the pointer.
- switch (AA->getModRefInfo(Inst, MemLoc)) {
+ switch (getModRefInfo(Inst, MemLoc)) {
case AliasAnalysis::NoModRef:
// If the call has no effect on the queried pointer, just ignore it.
continue;
// unknown, otherwise it is non-local.
if (BB != &BB->getParent()->getEntryBlock())
return MemDepResult::getNonLocal();
- return MemDepResult::getUnknown();
+ return MemDepResult::getNonFuncLocal();
}
/// getDependency - Return the instruction on which a memory operation
if (QueryParent != &QueryParent->getParent()->getEntryBlock())
LocalCache = MemDepResult::getNonLocal();
else
- LocalCache = MemDepResult::getUnknown();
+ LocalCache = MemDepResult::getNonFuncLocal();
} else {
AliasAnalysis::Location MemLoc;
AliasAnalysis::ModRefResult MR = GetLocation(QueryInst, MemLoc, AA);
// a clobber, otherwise it is unknown.
Dep = MemDepResult::getNonLocal();
} else {
- Dep = MemDepResult::getUnknown();
+ Dep = MemDepResult::getNonFuncLocal();
}
// If we had a dirty entry for the block, update it. Otherwise, just add
// If the block has a dependency (i.e. it isn't completely transparent to
// the value), remember the reverse association because we just added it
// to Cache!
- if (Dep.isNonLocal() || Dep.isUnknown())
+ if (!Dep.isDef() && !Dep.isClobber())
return Dep;
// Keep the ReverseNonLocalPtrDeps map up to date so we can efficiently
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