[llvm] [WIP][DAG] Add legalization handling for AVGCEIL/AVGFLOOR nodes (PR #92096)

[Simon Pilgrim via llvm-commits]

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@@ -39,8 +39,10 @@ define <8 x i8> @vaaddu_vv_v8i8_floor_sexti16(<8 x i8> %x, <8 x i8> %y) {
 ; CHECK-LABEL: vaaddu_vv_v8i8_floor_sexti16:
 ; CHECK:       # %bb.0:
 ; CHECK-NEXT:    vsetivli zero, 8, e8, mf2, ta, ma
-; CHECK-NEXT:    vwadd.vv v10, v8, v9
-; CHECK-NEXT:    vnsrl.wi v8, v10, 1
+; CHECK-NEXT:    vand.vv v10, v8, v9
+; CHECK-NEXT:    vxor.vv v8, v8, v9
+; CHECK-NEXT:    vsra.vi v8, v8, 1
+; CHECK-NEXT:    vadd.vv v8, v10, v8
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RKSimon wrote:

@topperc Would it be acceptable to just add avgfloors/avgflooru custom lowering to riscv? I'm not sure how better we can make use the vwadd widening add instruction.

https://github.com/llvm/llvm-project/pull/92096