[PATCH] D50840: [InstCombine] Extend collectShuffleElements to support extract/zext/insert patterns

[Roman Lebedev via Phabricator via llvm-commits]

lebedev.ri added a comment.

1. Why is this limited to extensions? Why can't this also be done for `trunc`? Or more generally, why don't we want to do this if the same operation is applied for all the elements?
2. Do the vectorizer passes handle this? (Especially in light of the last question of `1.`)



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Comment at: lib/Transforms/InstCombine/InstCombineVectorOps.cpp:477
+    if(ExtOpc)
+      if (CastInst *ZI = dyn_cast<CastInst>(ScalarOp))
+        if (ZI->getOpcode() == *ExtOpc)
----------------
Why `ZI`?
Is this limited to `zext`?
`CI` perhaps?


================
Comment at: lib/Transforms/InstCombine/InstCombineVectorOps.cpp:801
+  Optional<Instruction::CastOps> ExtOpc = None;
+  if (CastInst *ZI = dyn_cast<CastInst>(ScalarOp)) {
+    if (ZI->getOpcode() == Instruction::ZExt ||
----------------
Same


Repository:
  rL LLVM

https://reviews.llvm.org/D50840