enhance memcpy opt to turn memmoves into memcpy when the src/dest
don't alias. Remove an old and poorly reduced testcase that fails
with this transform for reasons unrelated to the original test.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@80693 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Scalar/MemCpyOptimizer.cpp b/lib/Transforms/Scalar/MemCpyOptimizer.cpp
index cd89235..a158f0a 100644
--- a/lib/Transforms/Scalar/MemCpyOptimizer.cpp
+++ b/lib/Transforms/Scalar/MemCpyOptimizer.cpp
@@ -317,6 +317,7 @@
// Helper fuctions
bool processStore(StoreInst *SI, BasicBlock::iterator &BBI);
bool processMemCpy(MemCpyInst *M);
+ bool processMemMove(MemMoveInst *M);
bool performCallSlotOptzn(MemCpyInst *cpy, CallInst *C);
bool iterateOnFunction(Function &F);
};
@@ -431,9 +432,8 @@
BasicBlock::iterator InsertPt = BI;
if (MemSetF == 0) {
- const Type *Tys[] = {Type::getInt64Ty(SI->getContext())};
- MemSetF = Intrinsic::getDeclaration(M, Intrinsic::memset,
- Tys, 1);
+ const Type *Ty = Type::getInt64Ty(SI->getContext());
+ MemSetF = Intrinsic::getDeclaration(M, Intrinsic::memset, &Ty, 1);
}
// Get the starting pointer of the block.
@@ -679,11 +679,10 @@
return false;
// If all checks passed, then we can transform these memcpy's
- const Type *Tys[1];
- Tys[0] = M->getLength()->getType();
+ const Type *Ty = M->getLength()->getType();
Function *MemCpyFun = Intrinsic::getDeclaration(
M->getParent()->getParent()->getParent(),
- M->getIntrinsicID(), Tys, 1);
+ M->getIntrinsicID(), &Ty, 1);
Value *Args[4] = {
M->getRawDest(), MDep->getRawSource(), M->getLength(), M->getAlignmentCst()
@@ -708,6 +707,36 @@
return false;
}
+/// processMemMove - Transforms memmove calls to memcpy calls when the src/dst
+/// are guaranteed not to alias.
+bool MemCpyOpt::processMemMove(MemMoveInst *M) {
+ AliasAnalysis &AA = getAnalysis<AliasAnalysis>();
+
+ // If the memmove is a constant size, use it for the alias query, this allows
+ // us to optimize things like: memmove(P, P+64, 64);
+ uint64_t MemMoveSize = ~0ULL;
+ if (ConstantInt *Len = dyn_cast<ConstantInt>(M->getLength()))
+ MemMoveSize = Len->getZExtValue();
+
+ // See if the pointers alias.
+ if (AA.alias(M->getRawDest(), MemMoveSize, M->getRawSource(), MemMoveSize) !=
+ AliasAnalysis::NoAlias)
+ return false;
+
+ DEBUG(errs() << "MemCpyOpt: Optimizing memmove -> memcpy: " << *M << "\n");
+
+ // If not, then we know we can transform this.
+ Module *Mod = M->getParent()->getParent()->getParent();
+ const Type *Ty = M->getLength()->getType();
+ M->setOperand(0, Intrinsic::getDeclaration(Mod, Intrinsic::memcpy, &Ty, 1));
+
+ // MemDep may have over conservative information about this instruction, just
+ // conservatively flush it from the cache.
+ getAnalysis<MemoryDependenceAnalysis>().removeInstruction(M);
+ return true;
+}
+
+
// MemCpyOpt::iterateOnFunction - Executes one iteration of GVN.
bool MemCpyOpt::iterateOnFunction(Function &F) {
bool MadeChange = false;
@@ -723,6 +752,12 @@
MadeChange |= processStore(SI, BI);
else if (MemCpyInst *M = dyn_cast<MemCpyInst>(I))
MadeChange |= processMemCpy(M);
+ else if (MemMoveInst *M = dyn_cast<MemMoveInst>(I)) {
+ if (processMemMove(M)) {
+ --BI; // Reprocess the new memcpy.
+ MadeChange = true;
+ }
+ }
}
}