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-rw-r--r--lib/Analysis/MemoryDependenceAnalysis.cpp67
1 files changed, 32 insertions, 35 deletions
diff --git a/lib/Analysis/MemoryDependenceAnalysis.cpp b/lib/Analysis/MemoryDependenceAnalysis.cpp
index 6d38863..716e3e6 100644
--- a/lib/Analysis/MemoryDependenceAnalysis.cpp
+++ b/lib/Analysis/MemoryDependenceAnalysis.cpp
@@ -93,8 +93,6 @@ void MemoryDependenceAnalysis::getAnalysisUsage(AnalysisUsage &AU) const {
bool MemoryDependenceAnalysis::runOnFunction(Function &F) {
AA = &getAnalysis<AliasAnalysis>();
AC = &getAnalysis<AssumptionCacheTracker>().getAssumptionCache(F);
- DataLayoutPass *DLP = getAnalysisIfAvailable<DataLayoutPass>();
- DL = DLP ? &DLP->getDataLayout() : nullptr;
DominatorTreeWrapperPass *DTWP =
getAnalysisIfAvailable<DominatorTreeWrapperPass>();
DT = DTWP ? &DTWP->getDomTree() : nullptr;
@@ -263,22 +261,17 @@ getCallSiteDependencyFrom(CallSite CS, bool isReadOnlyCall,
///
/// MemLocBase, MemLocOffset are lazily computed here the first time the
/// base/offs of memloc is needed.
-static bool
-isLoadLoadClobberIfExtendedToFullWidth(const AliasAnalysis::Location &MemLoc,
- const Value *&MemLocBase,
- int64_t &MemLocOffs,
- const LoadInst *LI,
- const DataLayout *DL) {
- // If we have no target data, we can't do this.
- if (!DL) return false;
+static bool isLoadLoadClobberIfExtendedToFullWidth(
+ const AliasAnalysis::Location &MemLoc, const Value *&MemLocBase,
+ int64_t &MemLocOffs, const LoadInst *LI) {
+ const DataLayout &DL = LI->getModule()->getDataLayout();
// If we haven't already computed the base/offset of MemLoc, do so now.
if (!MemLocBase)
MemLocBase = GetPointerBaseWithConstantOffset(MemLoc.Ptr, MemLocOffs, DL);
- unsigned Size = MemoryDependenceAnalysis::
- getLoadLoadClobberFullWidthSize(MemLocBase, MemLocOffs, MemLoc.Size,
- LI, *DL);
+ unsigned Size = MemoryDependenceAnalysis::getLoadLoadClobberFullWidthSize(
+ MemLocBase, MemLocOffs, MemLoc.Size, LI);
return Size != 0;
}
@@ -289,10 +282,9 @@ isLoadLoadClobberIfExtendedToFullWidth(const AliasAnalysis::Location &MemLoc,
/// 2) safe for the target, and 3) would provide the specified memory
/// location value, then this function returns the size in bytes of the
/// load width to use. If not, this returns zero.
-unsigned MemoryDependenceAnalysis::
-getLoadLoadClobberFullWidthSize(const Value *MemLocBase, int64_t MemLocOffs,
- unsigned MemLocSize, const LoadInst *LI,
- const DataLayout &DL) {
+unsigned MemoryDependenceAnalysis::getLoadLoadClobberFullWidthSize(
+ const Value *MemLocBase, int64_t MemLocOffs, unsigned MemLocSize,
+ const LoadInst *LI) {
// We can only extend simple integer loads.
if (!isa<IntegerType>(LI->getType()) || !LI->isSimple()) return 0;
@@ -301,10 +293,12 @@ getLoadLoadClobberFullWidthSize(const Value *MemLocBase, int64_t MemLocOffs,
if (LI->getParent()->getParent()->hasFnAttribute(Attribute::SanitizeThread))
return 0;
+ const DataLayout &DL = LI->getModule()->getDataLayout();
+
// Get the base of this load.
int64_t LIOffs = 0;
const Value *LIBase =
- GetPointerBaseWithConstantOffset(LI->getPointerOperand(), LIOffs, &DL);
+ GetPointerBaseWithConstantOffset(LI->getPointerOperand(), LIOffs, DL);
// If the two pointers are not based on the same pointer, we can't tell that
// they are related.
@@ -413,14 +407,19 @@ getPointerDependencyFrom(const AliasAnalysis::Location &MemLoc, bool isLoad,
// by every program that can detect any optimisation of that kind: either
// it is racy (undefined) or there is a release followed by an acquire
// between the pair of accesses under consideration.
- bool HasSeenAcquire = false;
+ // If the load is invariant, we "know" that it doesn't alias *any* write. We
+ // do want to respect mustalias results since defs are useful for value
+ // forwarding, but any mayalias write can be assumed to be noalias.
+ // Arguably, this logic should be pushed inside AliasAnalysis itself.
if (isLoad && QueryInst) {
LoadInst *LI = dyn_cast<LoadInst>(QueryInst);
if (LI && LI->getMetadata(LLVMContext::MD_invariant_load) != nullptr)
isInvariantLoad = true;
}
+ const DataLayout &DL = BB->getModule()->getDataLayout();
+
// Walk backwards through the basic block, looking for dependencies.
while (ScanIt != BB->begin()) {
Instruction *Inst = --ScanIt;
@@ -472,12 +471,12 @@ getPointerDependencyFrom(const AliasAnalysis::Location &MemLoc, bool isLoad,
// Atomic loads have complications involved.
// A Monotonic (or higher) load is OK if the query inst is itself not atomic.
- // An Acquire (or higher) load sets the HasSeenAcquire flag, so that any
- // release store will know to return getClobber.
// FIXME: This is overly conservative.
if (LI->isAtomic() && LI->getOrdering() > Unordered) {
if (!QueryInst)
return MemDepResult::getClobber(LI);
+ if (LI->getOrdering() != Monotonic)
+ return MemDepResult::getClobber(LI);
if (auto *QueryLI = dyn_cast<LoadInst>(QueryInst)) {
if (!QueryLI->isSimple())
return MemDepResult::getClobber(LI);
@@ -487,9 +486,6 @@ getPointerDependencyFrom(const AliasAnalysis::Location &MemLoc, bool isLoad,
} else if (QueryInst->mayReadOrWriteMemory()) {
return MemDepResult::getClobber(LI);
}
-
- if (isAtLeastAcquire(LI->getOrdering()))
- HasSeenAcquire = true;
}
AliasAnalysis::Location LoadLoc = AA->getLocation(LI);
@@ -505,12 +501,12 @@ getPointerDependencyFrom(const AliasAnalysis::Location &MemLoc, bool isLoad,
// location is 1 byte at P+1). If so, return it as a load/load
// clobber result, allowing the client to decide to widen the load if
// it wants to.
- if (IntegerType *ITy = dyn_cast<IntegerType>(LI->getType()))
- if (LI->getAlignment()*8 > ITy->getPrimitiveSizeInBits() &&
+ if (IntegerType *ITy = dyn_cast<IntegerType>(LI->getType())) {
+ if (LI->getAlignment() * 8 > ITy->getPrimitiveSizeInBits() &&
isLoadLoadClobberIfExtendedToFullWidth(MemLoc, MemLocBase,
- MemLocOffset, LI, DL))
+ MemLocOffset, LI))
return MemDepResult::getClobber(Inst);
-
+ }
continue;
}
@@ -549,12 +545,12 @@ getPointerDependencyFrom(const AliasAnalysis::Location &MemLoc, bool isLoad,
if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
// Atomic stores have complications involved.
// A Monotonic store is OK if the query inst is itself not atomic.
- // A Release (or higher) store further requires that no acquire load
- // has been seen.
// FIXME: This is overly conservative.
if (!SI->isUnordered()) {
if (!QueryInst)
return MemDepResult::getClobber(SI);
+ if (SI->getOrdering() != Monotonic)
+ return MemDepResult::getClobber(SI);
if (auto *QueryLI = dyn_cast<LoadInst>(QueryInst)) {
if (!QueryLI->isSimple())
return MemDepResult::getClobber(SI);
@@ -564,9 +560,6 @@ getPointerDependencyFrom(const AliasAnalysis::Location &MemLoc, bool isLoad,
} else if (QueryInst->mayReadOrWriteMemory()) {
return MemDepResult::getClobber(SI);
}
-
- if (HasSeenAcquire && isAtLeastRelease(SI->getOrdering()))
- return MemDepResult::getClobber(SI);
}
// FIXME: this is overly conservative.
@@ -612,6 +605,8 @@ getPointerDependencyFrom(const AliasAnalysis::Location &MemLoc, bool isLoad,
if (AccessPtr == Inst || AA->isMustAlias(Inst, AccessPtr))
return MemDepResult::getDef(Inst);
+ if (isInvariantLoad)
+ continue;
// Be conservative if the accessed pointer may alias the allocation.
if (AA->alias(Inst, AccessPtr) != AliasAnalysis::NoAlias)
return MemDepResult::getClobber(Inst);
@@ -622,6 +617,9 @@ getPointerDependencyFrom(const AliasAnalysis::Location &MemLoc, bool isLoad,
continue;
}
+ if (isInvariantLoad)
+ continue;
+
// See if this instruction (e.g. a call or vaarg) mod/ref's the pointer.
AliasAnalysis::ModRefResult MR = AA->getModRefInfo(Inst, MemLoc);
// If necessary, perform additional analysis.
@@ -923,8 +921,7 @@ getNonLocalPointerDependency(Instruction *QueryInst,
const_cast<Value *>(Loc.Ptr)));
return;
}
-
-
+ const DataLayout &DL = FromBB->getModule()->getDataLayout();
PHITransAddr Address(const_cast<Value *>(Loc.Ptr), DL, AC);
// This is the set of blocks we've inspected, and the pointer we consider in
generated by cgit v1.1 at 2024-12-22 11:41:11 +0000