[PATCH] D56633: [WebAssembly] Optimize BUILD_VECTOR lowering for size

[Heejin Ahn via Phabricator via llvm-commits]

aheejin added inline comments.


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Comment at: test/CodeGen/WebAssembly/simd-build-vector.ll:116
+; CHECK-NEXT:  .functype       all_undef_i8x16 () -> (v128)
+; CHECK-NEXT:  return          $0
+define <16 x i8> @all_undef_i8x16() {
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aheejin wrote:
> Looking at the code above, I wonder how we ended up with a `local.get` from an unassigned local here for all undef case. Actually it works beautifully, given that unassigned locals are zero-initialized by default and it is even less space than `splat 0`. Maybe this can be an optimization in which we try to replace all `v128.const 0, ..., 0` and `splat 0` with `local.get n` where n being an assigned local. Just a thought and not relevant to this CL.
Hmm, it seems ExplicitLocals pass turns all unstackified registers to locals in which undefined registers become `local.get` from unassigned locals. And I don't think the current SIMD backend would prefer `v128.const 0, ..., 0` over `splat 0` anyway, right? So sorry, nevermind. :)


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  rL LLVM

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  https://reviews.llvm.org/D56633/new/

https://reviews.llvm.org/D56633