[PATCH] D102920: [SLP]Better detection of perfect/shuffles matches for gather nodes.

[Eric Christopher via Phabricator via llvm-commits]

echristo added a comment.

Given the iterations here I think that it needs a lot of inline documentation for cost model of what you're doing and what it's expecting here.



================
Comment at: llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp:3708
+    }
+    if (isSplat(VL)) {
+      return ReuseShuffleCost +
----------------
This needs to be documented as to what you're doing and what it means in the code.


================
Comment at: llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp:3713
     }
-    return ReuseShuffleCost + GatherCost;
+    if (E->getOpcode() == Instruction::ExtractElement && allSameType(VL) &&
+        allSameBlock(VL)) {
----------------
Same :)


================
Comment at: llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp:4431
+  // found not a shuffle.
+  SmallVector<SmallPtrSet<const TreeEntry *, 4>> UsedTEs;
+  DenseMap<Value *, int> UsedValuesEntry;
----------------
Please document this :)


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  https://reviews.llvm.org/D102920/new/

https://reviews.llvm.org/D102920