-AliasAnalysis::DependenceResult
-AliasAnalysis::getDependenceViaModRefInfo(const Instruction *First,
- const Value *FirstPHITranslatedAddr,
- DependenceQueryFlags FirstFlags,
- const Instruction *Second,
- const Value *SecondPHITranslatedAddr,
- DependenceQueryFlags SecondFlags) {
- if (const LoadInst *L = dyn_cast<LoadInst>(First)) {
- // Be over-conservative with volatile for now.
- if (L->isVolatile())
- return Unknown;
-
- // If we don't have a phi-translated address, use the actual one.
- if (!FirstPHITranslatedAddr)
- FirstPHITranslatedAddr = L->getPointerOperand();
-
- // Forward this query to getModRefInfo.
- switch (getModRefInfo(Second,
- FirstPHITranslatedAddr,
- 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)) {
- // If we don't have a phi-translated address, use the actual one.
- if (!SecondPHITranslatedAddr)
- SecondPHITranslatedAddr = SecondL->getPointerOperand();
-
- unsigned LSize = getTypeStoreSize(L->getType());
- unsigned SecondLSize = getTypeStoreSize(SecondL->getType());
- if (alias(FirstPHITranslatedAddr, LSize,
- SecondPHITranslatedAddr, 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)) {
- // If we don't have a phi-translated address, use the actual one.
- if (!SecondPHITranslatedAddr)
- SecondPHITranslatedAddr = SecondS->getPointerOperand();
-
- unsigned LSize = getTypeStoreSize(L->getType());
- unsigned SecondSSize = getTypeStoreSize(SecondS->getType());
- if (alias(FirstPHITranslatedAddr, LSize,
- SecondPHITranslatedAddr, SecondSSize) ==
- MustAlias) {
- // If the load and the store are the same size, it's ReadThenWrite.
- if (LSize == SecondSSize)
- return ReadThenWrite;
- }
- }