[llvm] [AArch64] Improve index selection for histograms (PR #111150)

[Graham Hunter via llvm-commits]

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@@ -267,5 +267,79 @@ define void @histogram_i16_8_lane(ptr %base, <vscale x 8 x i32> %indices, i16 %i
   ret void
 }
 
+define void @histogram_i32_zextend(ptr %base, <vscale x 4 x i32> %indices, <vscale x 4 x i1> %mask) #0 {
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huntergr-arm wrote:

Yes, that's pretty much what we want -- if it's possible to use a 32b index type, we'd prefer to do so because we can process twice as much data that way. My idea was to reuse the existing logic for gathers and scatters (which does the same thing for the same reasons), and I believe handles more cases than just extends.

But I'll take incremental progress with just supporting extends to begin with :)

https://github.com/llvm/llvm-project/pull/111150