/// circumstances). This allows later passes to remove the first memcpy
/// altogether.
bool MemCpyOpt::processMemCpy(MemCpyInst *M) {
- // We can only optimize statically-sized memcpy's that are non-volatile.
- ConstantInt *CopySize = dyn_cast<ConstantInt>(M->getLength());
- if (CopySize == 0 || M->isVolatile()) return false;
+ // We can only optimize non-volatile memcpy's.
+ if (M->isVolatile()) return false;
// If the source and destination of the memcpy are the same, then zap it.
if (M->getSource() == M->getDest()) {
if (GV->isConstant() && GV->hasDefinitiveInitializer())
if (Value *ByteVal = isBytewiseValue(GV->getInitializer())) {
IRBuilder<> Builder(M);
- Builder.CreateMemSet(M->getRawDest(), ByteVal, CopySize,
+ Builder.CreateMemSet(M->getRawDest(), ByteVal, M->getLength(),
M->getAlignment(), false);
MD->removeInstruction(M);
M->eraseFromParent();
return true;
}
+ // The optimizations after this point require the memcpy size.
+ ConstantInt *CopySize = dyn_cast<ConstantInt>(M->getLength());
+ if (CopySize == 0) return false;
+
// The are two possible optimizations we can do for memcpy:
// a) memcpy-memcpy xform which exposes redundance for DSE.
// b) call-memcpy xform for return slot optimization.