[PATCH] D56281: [DAGCombiner] reduce buildvec of zexted extracted element to shuffle

[Sanjay Patel via llvm-commits]

Thanks for letting me know - I suspect I failed to account for a build
vector whose elements are not the same size as the build vector type.
Taking a look now.

On Mon, Jan 21, 2019 at 9:04 AM Sjoerd Meijer via Phabricator <
reviews at reviews.llvm.org> wrote:

> SjoerdMeijer added a comment.
>
> Hello. I am investigating a crash and this assertion failure on AArch64:
>
>   lib/CodeGen/SelectionDAG/SelectionDAG.cpp:1548: llvm::SDValue
> llvm::SelectionDAG::getVectorShuffle(llvm::EVT, const llvm::SDLoc&,
> llvm::SDValue, llvm::SDValue, llvm::ArrayRef<int>): Assertion
> `VT.getVectorNumElements() == Mask.size() && "Must have the same number of
> vector elements as mask elements!"' failed.
>
> Bisecting is blaming this commit. I've only just started debugging this
> (and it is hitting this new function), but just wanted to share this in
> case you have some ideas and thoughts on this. This is my reproducer:
>
>   target datalayout = "e-m:e-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128"
>   target triple = "aarch64-unknown-linux-gnu"
>
>   @a = common dso_local local_unnamed_addr global <4 x i16>
> zeroinitializer, align 8
>   @b = common dso_local local_unnamed_addr global i32 0, align 4
>
>   ; Function Attrs: nounwind
>   define dso_local i32 @vqmovns_s32() local_unnamed_addr {
>   entry:
>     %0 = load <4 x i16>, <4 x i16>* @a, align 8
>     %1 = extractelement <4 x i16> %0, i32 2
>     %vgetq_lane = zext i16 %1 to i32
>     %2 = insertelement <4 x i32> undef, i32 %vgetq_lane, i64 0
>     %vqmovns_s32 = tail call <4 x i16> @llvm.aarch64.neon.sqxtn.v4i16(<4 x
> i32> %2)
>     %3 = extractelement <4 x i16> %vqmovns_s32, i64 0
>     %conv = sext i16 %3 to i32
>     store i32 %conv, i32* @b, align 4
>     ret i32 undef
>   }
>
>   ; Function Attrs: nounwind readnone
>   declare <4 x i16> @llvm.aarch64.neon.sqxtn.v4i16(<4 x i32>)
>
>
> Repository:
>   rL LLVM
>
> CHANGES SINCE LAST ACTION
>   https://reviews.llvm.org/D56281/new/
>
> https://reviews.llvm.org/D56281
>
>
>
>
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