[PATCH] D74322: GlobalISel: Extend narrowing to G_ASHR

[Jay Foad via Phabricator via llvm-commits]

foad added inline comments.


================
Comment at: llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp:1493
+      // (G_ASHR i64:x, 63) ->
+      //   G_MERGE_VALUES (G_ASHR hi_32(x), 31), (G_ASHR hi_32(x), 31)
+      Builder.buildMerge(DstReg, { Hi, Hi });
----------------
foad wrote:
> Why not generalize this to:
> ```
> (G_ASHR i64:x, 63) for C >= 32 ->
>   G_MERGE_VALUES (G_ASHR hi_32(x), C-32), (G_ASHR hi_32(x), 31)
> ```
> ?
I meant `(G_ASHR i64:x, C)` of course.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D74322/new/

https://reviews.llvm.org/D74322