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Weak relaxing of the constraints on atomics in MemoryDependencyAnalysis

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Monotonic accesses do not have to kill the analysis, as long as the QueryInstr is not
itself atomic.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@215942 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Robin Morisset
2014-08-18 22:18:11 +00:00
parent 08f77a9f42
commit 6c0e1e0fa6
2 changed files with 69 additions and 4 deletions
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26
lib/Analysis/MemoryDependenceAnalysis.cpp
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@ -409,9 +409,18 @@ getPointerDependencyFrom(const AliasAnalysis::Location &MemLoc, bool isLoad,
// a load depends on another must aliased load from the same value.
if (LoadInst *LI = dyn_cast<LoadInst>(Inst)) {
// Atomic loads have complications involved.
// A monotonic load is OK if the query inst is itself not atomic.
// FIXME: This is overly conservative.
if (!LI->isUnordered())
return MemDepResult::getClobber(LI);
if (!LI->isUnordered()) {
if (!QueryInst || LI->getOrdering() != Monotonic)
return MemDepResult::getClobber(LI);
if (auto *QueryLI = dyn_cast<LoadInst>(QueryInst))
if (!QueryLI->isUnordered())
return MemDepResult::getClobber(LI);
if (auto *QuerySI = dyn_cast<StoreInst>(QueryInst))
if (!QuerySI->isUnordered())
return MemDepResult::getClobber(LI);
}
AliasAnalysis::Location LoadLoc = AA->getLocation(LI);
@ -469,9 +478,18 @@ 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.
// FIXME: This is overly conservative.
if (!SI->isUnordered())
return MemDepResult::getClobber(SI);
if (!SI->isUnordered()) {
if (!QueryInst || SI->getOrdering() != Monotonic)
return MemDepResult::getClobber(SI);
if (auto *QueryLI = dyn_cast<LoadInst>(QueryInst))
if (!QueryLI->isUnordered())
return MemDepResult::getClobber(SI);
if (auto *QuerySI = dyn_cast<StoreInst>(QueryInst))
if (!QuerySI->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