[PATCH] D30653: [LV] Refactor Cost Model's selectVectorizationFactor(), driven by a LoopVectorizationPlanner

[Michael Kuperstein via Phabricator via llvm-commits]

mkuper added inline comments.


================
Comment at: lib/Transforms/Vectorize/LoopVectorize.cpp:6163
 
-LoopVectorizationCostModel::VectorizationFactor
-LoopVectorizationCostModel::selectVectorizationFactor(bool OptForSize) {
-  // Width 1 means no vectorize
-  VectorizationFactor Factor = {1U, 0U};
-  if (OptForSize && Legal->getRuntimePointerChecking()->Need) {
+unsigned LoopVectorizationCostModel::computeMaxVFOrFail(bool OptForSize) {
+  const unsigned Fail = 0;
----------------
Any reason not to use Optional<> instead?


================
Comment at: lib/Transforms/Vectorize/LoopVectorize.cpp:7385
+    DEBUG(dbgs() << "LV: Using user VF " << UserVF << ".\n");
+    if (UserVF == 1)
+      return {UserVF, 0};
----------------
Maybe:
```
DEBUG(dbgs() << "LV: Using user VF " << UserVF << ".\n");
assert(isPowerOf2_32(UserVF) && "VF needs to be a power of two");
if (UserVF != 1)
  CM.selectUserVectorizationFactor(UserVF);
return {UserVF, 0}
```
?

(I think isPowerOf2_32(1) is true.)


https://reviews.llvm.org/D30653