[SLP] Update the debug based on Michael's suggestion.

Passing the types/opcode check still doesn't guarantee we'll actually vectorize.
Therefore, just make it clear we're attempting to vectorize.

llvm-svn: 280263

llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp

@@ -3855,6 +3855,9 @@ bool SLPVectorizerPass::tryToVectorizeList(ArrayRef<Value *> VL, BoUpSLP &R,
   if (VL.size() < 2)
     return false;
 
+  DEBUG(dbgs() << "SLP: Trying to vectorize a list of length = " << VL.size()
+               << ".\n");
+
   // Check that all of the parts are scalar instructions of the same type.
   Instruction *I0 = dyn_cast<Instruction>(VL[0]);
   if (!I0)
@@ -3876,8 +3879,6 @@ bool SLPVectorizerPass::tryToVectorizeList(ArrayRef<Value *> VL, BoUpSLP &R,
       return false;
   }
 
-  DEBUG(dbgs() << "SLP: Vectorizing a list of length = " << VL.size() << ".\n");
-
   bool Changed = false;
 
   // Keep track of values that were deleted by vectorizing in the loop below.