[llvm] [LLVM][DAGCombiner] Improve simplifyDivRem's effectiveness after type legalisation. (PR #162706)

[Matt Arsenault via llvm-commits]

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@@ -1774,3 +1774,88 @@ define i128 @combine_i128_sdiv_const100(i128 %x) {
   %1 = sdiv i128 %x, 100
   ret i128 %1
 }
+
+; The following only becomes an sdiv_by_one after type legalisation, after which
+; the splatted scalar constant has a different type to the splat vector. This
+; test verifies DAGCombiner does not care about this type difference.
+define <16 x i16> @combine_vec_sdiv_by_one_obfuscated(<16 x i16> %x) "target-features"="+sve" {
+; CHECK-SD-LABEL: combine_vec_sdiv_by_one_obfuscated:
+; CHECK-SD:       // %bb.0:
+; CHECK-SD-NEXT:    ret
+;
+; CHECK-GI-LABEL: combine_vec_sdiv_by_one_obfuscated:
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arsenm wrote:

It doesn't have any of these combines 

https://github.com/llvm/llvm-project/pull/162706