+
+ auto *T = LI->getType();
+ if (T->isAggregateType()) {
+ AliasAnalysis &AA = getAnalysis<AAResultsWrapperPass>().getAAResults();
+ MemoryLocation LoadLoc = MemoryLocation::get(LI);
+
+ // We use alias analysis to check if an instruction may store to
+ // the memory we load from in between the load and the store. If
+ // such an instruction is found, we try to promote there instead
+ // of at the store position.
+ Instruction *P = SI;
+ for (BasicBlock::iterator I = ++LI->getIterator(), E = SI->getIterator();
+ I != E; ++I) {
+ if (!(AA.getModRefInfo(&*I, LoadLoc) & MRI_Mod))
+ continue;
+
+ // We found an instruction that may write to the loaded memory.
+ // We can try to promote at this position instead of the store
+ // position if nothing alias the store memory after this.
+ P = &*I;
+ for (; I != E; ++I) {
+ MemoryLocation StoreLoc = MemoryLocation::get(SI);
+ if (AA.getModRefInfo(&*I, StoreLoc) != MRI_NoModRef) {
+ P = nullptr;
+ break;
+ }
+ }
+
+ break;
+ }
+
+ // If a valid insertion position is found, then we can promote
+ // the load/store pair to a memcpy.
+ if (P) {
+ // If we load from memory that may alias the memory we store to,
+ // memmove must be used to preserve semantic. If not, memcpy can
+ // be used.
+ bool UseMemMove = false;
+ if (!AA.isNoAlias(MemoryLocation::get(SI), LoadLoc))
+ UseMemMove = true;
+
+ unsigned Align = findCommonAlignment(DL, SI, LI);
+ uint64_t Size = DL.getTypeStoreSize(T);
+
+ IRBuilder<> Builder(P);
+ Instruction *M;
+ if (UseMemMove)
+ M = Builder.CreateMemMove(SI->getPointerOperand(),
+ LI->getPointerOperand(), Size,
+ Align, SI->isVolatile());
+ else
+ M = Builder.CreateMemCpy(SI->getPointerOperand(),
+ LI->getPointerOperand(), Size,
+ Align, SI->isVolatile());
+
+ DEBUG(dbgs() << "Promoting " << *LI << " to " << *SI
+ << " => " << *M << "\n");
+
+ MD->removeInstruction(SI);
+ SI->eraseFromParent();
+ MD->removeInstruction(LI);
+ LI->eraseFromParent();
+ ++NumMemCpyInstr;
+
+ // Make sure we do not invalidate the iterator.
+ BBI = M->getIterator();
+ return true;
+ }
+ }
+
+ // Detect cases where we're performing call slot forwarding, but
+ // happen to be using a load-store pair to implement it, rather than
+ // a memcpy.