[PATCH] D83102: [Scalarizer] Constant InsertElement Hanlding

[Roman Lebedev via Phabricator via llvm-commits]

lebedev.ri created this revision.
lebedev.ri added reviewers: jdoerfert, arsenm, bjope, cameron.mcinally.
lebedev.ri added a project: LLVM.
Herald added subscribers: hiraditya, wdng.
lebedev.ri added a parent revision: D83101: [Scalarizer] Constant ExtractElement Hanlding.
lebedev.ri marked an inline comment as done.
lebedev.ri added inline comments.


================
Comment at: llvm/test/Transforms/Scalarizer/basic.ll:624
 
+; Test that constant inserts are nicely scalarized
+define <4 x i32> @f25(<4 x i32> *%src, i32 %repl, i32 %index) {
----------------
Previously we'd end up with https://godbolt.org/z/NyExWc
```
  %val0 = load <4 x i32>, <4 x i32>* %src, align 16
  %val1 = insertelement <4 x i32> %val0, i32 %repl, i32 3
  %val0.i0 = extractelement <4 x i32> %val0, i32 0
  %val2.i0 = shl i32 1, %val0.i0
  %val0.i1 = extractelement <4 x i32> %val0, i32 1
  %val2.i1 = shl i32 2, %val0.i1
  %val0.i2 = extractelement <4 x i32> %val0, i32 2
  %val2.i2 = shl i32 3, %val0.i2
  %val2.i3 = shl i32 4, %repl
  %val2.upto0 = insertelement <4 x i32> undef, i32 %val2.i0, i32 0
  %val2.upto1 = insertelement <4 x i32> %val2.upto0, i32 %val2.i1, i32 1
  %val2.upto2 = insertelement <4 x i32> %val2.upto1, i32 %val2.i2, i32 2
  %val2 = insertelement <4 x i32> %val2.upto2, i32 %val2.i3, i32 3
  ret <4 x i32> %val2
```


It appears to be better IR-wise to aggressively scalarize it,
rather than leaving it as-is.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D83102

Files:
  llvm/lib/Transforms/Scalar/Scalarizer.cpp
  llvm/test/Transforms/Scalarizer/basic.ll
  llvm/test/Transforms/Scalarizer/variable-insertelement.ll

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