Add a new experimental generalized dependence query interface to
AliasAnalysis, and some code for implementing the new query on top of
existing implementations by making standard alias and getModRefInfo
queries.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@113329 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Analysis/AliasAnalysis.cpp b/lib/Analysis/AliasAnalysis.cpp
index 1f2528f..536b759 100644
--- a/lib/Analysis/AliasAnalysis.cpp
+++ b/lib/Analysis/AliasAnalysis.cpp
@@ -188,6 +188,14 @@
return AA->getModRefBehavior(F);
}
+AliasAnalysis::DependenceResult
+AliasAnalysis::getDependence(const Instruction *First,
+ DependenceQueryFlags FirstFlags,
+ const Instruction *Second,
+ DependenceQueryFlags SecondFlags) {
+ assert(AA && "AA didn't call InitializeAliasAnalyais in its run method!");
+ return AA->getDependence(First, FirstFlags, Second, SecondFlags);
+}
//===----------------------------------------------------------------------===//
// AliasAnalysis non-virtual helper method implementation
@@ -245,6 +253,190 @@
return ModRef;
}
+AliasAnalysis::DependenceResult
+AliasAnalysis::getDependenceViaModRefInfo(const Instruction *First,
+ DependenceQueryFlags FirstFlags,
+ const Instruction *Second,
+ DependenceQueryFlags SecondFlags) {
+ if (const LoadInst *L = dyn_cast<LoadInst>(First)) {
+ // Be over-conservative with volatile for now.
+ if (L->isVolatile())
+ return Unknown;
+
+ // Forward this query to getModRefInfo.
+ switch (getModRefInfo(Second,
+ L->getPointerOperand(),
+ getTypeStoreSize(L->getType()))) {
+ case NoModRef:
+ // Second doesn't reference First's memory, so they're independent.
+ return Independent;
+
+ case Ref:
+ // Second only reads from the memory read from by First. If it
+ // also writes to any other memory, be conservative.
+ if (Second->mayWriteToMemory())
+ return Unknown;
+
+ // If it's loading the same size from the same address, we can
+ // give a more precise result.
+ if (const LoadInst *SecondL = dyn_cast<LoadInst>(Second)) {
+ unsigned LSize = getTypeStoreSize(L->getType());
+ unsigned SecondLSize = getTypeStoreSize(SecondL->getType());
+ if (alias(L->getPointerOperand(), LSize,
+ SecondL->getPointerOperand(), SecondLSize) ==
+ MustAlias) {
+ // If the loads are the same size, it's ReadThenRead.
+ if (LSize == SecondLSize)
+ return ReadThenRead;
+
+ // If the second load is smaller, it's only ReadThenReadSome.
+ if (LSize > SecondLSize)
+ return ReadThenReadSome;
+ }
+ }
+
+ // Otherwise it's just two loads.
+ return Independent;
+
+ case Mod:
+ // Second only writes to the memory read from by First. If it
+ // also reads from any other memory, be conservative.
+ if (Second->mayReadFromMemory())
+ return Unknown;
+
+ // If it's storing the same size to the same address, we can
+ // give a more precise result.
+ if (const StoreInst *SecondS = dyn_cast<StoreInst>(Second)) {
+ unsigned LSize = getTypeStoreSize(L->getType());
+ unsigned SecondSSize = getTypeStoreSize(SecondS->getType());
+ if (alias(L->getPointerOperand(), LSize,
+ SecondS->getPointerOperand(), SecondSSize) ==
+ MustAlias) {
+ // If the load and the store are the same size, it's ReadThenWrite.
+ if (LSize == SecondSSize)
+ return ReadThenWrite;
+ }
+ }
+
+ // Otherwise we don't know if it could be writing to other memory.
+ return Unknown;
+
+ case ModRef:
+ // Second reads and writes to the memory read from by First.
+ // We don't have a way to express that.
+ return Unknown;
+ }
+
+ } else if (const StoreInst *S = dyn_cast<StoreInst>(First)) {
+ // Be over-conservative with volatile for now.
+ if (S->isVolatile())
+ return Unknown;
+
+ // Forward this query to getModRefInfo.
+ switch (getModRefInfo(Second,
+ S->getPointerOperand(),
+ getTypeStoreSize(S->getValueOperand()->getType()))) {
+ case NoModRef:
+ // Second doesn't reference First's memory, so they're independent.
+ return Independent;
+
+ case Ref:
+ // Second only reads from the memory written to by First. If it
+ // also writes to any other memory, be conservative.
+ if (Second->mayWriteToMemory())
+ return Unknown;
+
+ // If it's loading the same size from the same address, we can
+ // give a more precise result.
+ if (const LoadInst *SecondL = dyn_cast<LoadInst>(Second)) {
+ unsigned SSize = getTypeStoreSize(S->getValueOperand()->getType());
+ unsigned SecondLSize = getTypeStoreSize(SecondL->getType());
+ if (alias(S->getPointerOperand(), SSize,
+ SecondL->getPointerOperand(), SecondLSize) ==
+ MustAlias) {
+ // If the store and the load are the same size, it's WriteThenRead.
+ if (SSize == SecondLSize)
+ return WriteThenRead;
+
+ // If the load is smaller, it's only WriteThenReadSome.
+ if (SSize > SecondLSize)
+ return WriteThenReadSome;
+ }
+ }
+
+ // Otherwise we don't know if it could be reading from other memory.
+ return Unknown;
+
+ case Mod:
+ // Second only writes to the memory written to by First. If it
+ // also reads from any other memory, be conservative.
+ if (Second->mayReadFromMemory())
+ return Unknown;
+
+ // If it's storing the same size to the same address, we can
+ // give a more precise result.
+ if (const StoreInst *SecondS = dyn_cast<StoreInst>(Second)) {
+ unsigned SSize = getTypeStoreSize(S->getValueOperand()->getType());
+ unsigned SecondSSize = getTypeStoreSize(SecondS->getType());
+ if (alias(S->getPointerOperand(), SSize,
+ SecondS->getPointerOperand(), SecondSSize) ==
+ MustAlias) {
+ // If the stores are the same size, it's WriteThenWrite.
+ if (SSize == SecondSSize)
+ return WriteThenWrite;
+
+ // If the second store is larger, it's only WriteSomeThenWrite.
+ if (SSize < SecondSSize)
+ return WriteSomeThenWrite;
+ }
+ }
+
+ // Otherwise we don't know if it could be writing to other memory.
+ return Unknown;
+
+ case ModRef:
+ // Second reads and writes to the memory written to by First.
+ // We don't have a way to express that.
+ return Unknown;
+ }
+
+ } else if (const VAArgInst *V = dyn_cast<VAArgInst>(First)) {
+ // Forward this query to getModRefInfo.
+ if (getModRefInfo(Second, V->getOperand(0), UnknownSize) == NoModRef)
+ // Second doesn't reference First's memory, so they're independent.
+ return Independent;
+
+ } else if (ImmutableCallSite FirstCS = cast<Value>(First)) {
+ // If both instructions are calls/invokes we can use the two-callsite
+ // form of getModRefInfo.
+ if (ImmutableCallSite SecondCS = cast<Value>(Second))
+ // getModRefInfo's arguments are backwards from intuition.
+ switch (getModRefInfo(SecondCS, FirstCS)) {
+ case NoModRef:
+ // Second doesn't reference First's memory, so they're independent.
+ return Independent;
+
+ case Ref:
+ // If they're both read-only, there's no dependence.
+ if (FirstCS.onlyReadsMemory() && SecondCS.onlyReadsMemory())
+ return Independent;
+
+ // Otherwise it's not obvious what we can do here.
+ return Unknown;
+
+ case Mod:
+ // It's not obvious what we can do here.
+ return Unknown;
+
+ case ModRef:
+ // I know, right?
+ return Unknown;
+ }
+ }
+
+ // For anything else, be conservative.
+ return Unknown;
+}
AliasAnalysis::ModRefBehavior
AliasAnalysis::getIntrinsicModRefBehavior(unsigned iid) {