[SLP] Sink debug after checking for matching types/opcode.

[mcrosier]

Summary

Trivial refactoring. I was working through a few of the existing lit test cases with debug enabled and I found it to be misleading to print this message and then immediate return because the types/opcode don't match.

Chad

[mssimpso]

LGTM!

[mkuper]

Maybe leave it where it is, but change the text from "Vectorizing" to "Trying to vectorize"?
With this patch it seems like it's neither here nor there - passing the "sameness" check still no guarantee we'll actually vectorize.

(Or even better, leave it where it is, change the text to "Trying to vectorize", and add another debug print once we pass the type/opcode check?)

[mkuper]

(I don't feel strongly about this, if both of you feel this is better, SGTM.)

[mcrosier]

In D24090#530573, @mkuper wrote:

(Or even better, leave it where it is, change the text to "Trying to vectorize", and add another debug print once we pass the type/opcode check?)

I committed this change, but I'll make your suggestion happen, Michael. Thanks.

[mcrosier]

In D24090#530580, @mcrosier wrote:

In D24090#530573, @mkuper wrote:

(Or even better, leave it where it is, change the text to "Trying to vectorize", and add another debug print once we pass the type/opcode check?)

I committed this change, but I'll make your suggestion happen, Michael. Thanks.

And now I'm leaning toward just changing the original statement to say "Trying to vectorize a list.."

llvm/trunk/lib/Transforms/Vectorize/SLPVectorizer.cpp

 }
 
 bool SLPVectorizerPass::tryToVectorizeList(ArrayRef<Value *> VL, BoUpSLP &R,
                                            ArrayRef<Value *> BuildVector,
                                            bool AllowReorder) {
   if (VL.size() < 2)
     return false;
 
-  DEBUG(dbgs() << "SLP: Vectorizing 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)
     return false;
 
   unsigned Opcode0 = I0->getOpcode();
 
   // FIXME: Register size should be a parameter to this function, so we can
   // try different vectorization factors.
   unsigned Sz = R.getVectorElementSize(I0);
   unsigned VF = R.getMinVecRegSize() / Sz;
 
   for (Value *V : VL) {
     Type *Ty = V->getType();
     if (!isValidElementType(Ty))
       return false;
     Instruction *Inst = dyn_cast<Instruction>(V);
     if (!Inst || Inst->getOpcode() != Opcode0)
       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.
   SmallVector<WeakVH, 8> TrackValues(VL.begin(), VL.end());
 
   for (unsigned i = 0, e = VL.size(); i < e; ++i) {
     unsigned OpsWidth = 0;