[memcpyopt] Add debug logs when forwarding memcpy src to dst

llvm-svn: 349873

llvm/lib/Transforms/Scalar/MemCpyOptimizer.cpp

@@ -1060,6 +1060,8 @@ bool MemCpyOptPass::processMemCpyMemCpyDependence(MemCpyInst *M,
     UseMemMove = true;
 
   // If all checks passed, then we can transform M.
+  LLVM_DEBUG(dbgs() << "MemCpyOptPass: Forwarding memcpy->memcpy src:\n"
+                    << *MDep << '\n' << *M << '\n');
 
   // TODO: Is this worth it if we're creating a less aligned memcpy? For
   // example we could be moving from movaps -> movq on x86.