[llvm] [GlobalISel] Combine away G_UNMERGE(G_IMPLICITDEF). (PR #119183)

[Dhruv Chawla via llvm-commits]

================
@@ -25,33 +22,66 @@
 ; CHECK-GI-NEXT:  warning: Instruction selection used fallback path for loaddup_v4fp128
 
 define <2 x i8> @dup_v2i8(i8 %a) {
-; CHECK-LABEL: dup_v2i8:
-; CHECK:       // %bb.0: // %entry
-; CHECK-NEXT:    dup v0.2s, w0
-; CHECK-NEXT:    ret
+; CHECK-SD-LABEL: dup_v2i8:
+; CHECK-SD:       // %bb.0: // %entry
+; CHECK-SD-NEXT:    dup v0.2s, w0
+; CHECK-SD-NEXT:    ret
+;
+; CHECK-GI-LABEL: dup_v2i8:
+; CHECK-GI:       // %bb.0: // %entry
+; CHECK-GI-NEXT:    dup v0.8b, w0
+; CHECK-GI-NEXT:    umov w8, v0.b[0]
+; CHECK-GI-NEXT:    umov w9, v0.b[1]
+; CHECK-GI-NEXT:    mov v0.s[0], w8
+; CHECK-GI-NEXT:    mov v0.s[1], w9
+; CHECK-GI-NEXT:    // kill: def $d0 killed $d0 killed $q0
+; CHECK-GI-NEXT:    ret
 entry:
   %b = insertelement <2 x i8> poison, i8 %a, i64 0
   %c = shufflevector <2 x i8> %b, <2 x i8> poison, <2 x i32> zeroinitializer
   ret <2 x i8> %c
 }
 
 define <2 x i8> @duplane0_v2i8(<2 x i8> %b) {
-; CHECK-LABEL: duplane0_v2i8:
-; CHECK:       // %bb.0: // %entry
-; CHECK-NEXT:    // kill: def $d0 killed $d0 def $q0
-; CHECK-NEXT:    dup v0.2s, v0.s[0]
-; CHECK-NEXT:    ret
+; CHECK-SD-LABEL: duplane0_v2i8:
+; CHECK-SD:       // %bb.0: // %entry
+; CHECK-SD-NEXT:    // kill: def $d0 killed $d0 def $q0
+; CHECK-SD-NEXT:    dup v0.2s, v0.s[0]
+; CHECK-SD-NEXT:    ret
+;
+; CHECK-GI-LABEL: duplane0_v2i8:
+; CHECK-GI:       // %bb.0: // %entry
+; CHECK-GI-NEXT:    // kill: def $d0 killed $d0 def $q0
+; CHECK-GI-NEXT:    mov w8, v0.s[1]
+; CHECK-GI-NEXT:    mov v0.b[1], w8
+; CHECK-GI-NEXT:    dup v0.8b, v0.b[0]
+; CHECK-GI-NEXT:    umov w8, v0.b[0]
+; CHECK-GI-NEXT:    umov w9, v0.b[1]
+; CHECK-GI-NEXT:    mov v0.s[0], w8
+; CHECK-GI-NEXT:    mov v0.s[1], w9
+; CHECK-GI-NEXT:    // kill: def $d0 killed $d0 killed $q0
+; CHECK-GI-NEXT:    ret
 entry:
   %c = shufflevector <2 x i8> %b, <2 x i8> poison, <2 x i32> zeroinitializer
   ret <2 x i8> %c
 }
 
 define <2 x i8> @loaddup_v2i8(ptr %p) {
-; CHECK-LABEL: loaddup_v2i8:
-; CHECK:       // %bb.0: // %entry
-; CHECK-NEXT:    ldrb w8, [x0]
-; CHECK-NEXT:    dup v0.2s, w8
-; CHECK-NEXT:    ret
+; CHECK-SD-LABEL: loaddup_v2i8:
+; CHECK-SD:       // %bb.0: // %entry
+; CHECK-SD-NEXT:    ldrb w8, [x0]
+; CHECK-SD-NEXT:    dup v0.2s, w8
+; CHECK-SD-NEXT:    ret
+;
+; CHECK-GI-LABEL: loaddup_v2i8:
+; CHECK-GI:       // %bb.0: // %entry
+; CHECK-GI-NEXT:    ld1r { v0.8b }, [x0]
+; CHECK-GI-NEXT:    umov w8, v0.b[0]
+; CHECK-GI-NEXT:    umov w9, v0.b[1]
+; CHECK-GI-NEXT:    mov v0.s[0], w8
+; CHECK-GI-NEXT:    mov v0.s[1], w9
+; CHECK-GI-NEXT:    // kill: def $d0 killed $d0 killed $q0
+; CHECK-GI-NEXT:    ret
----------------
dc03-work wrote:

This file seems to be regressing in codegen quality.

https://github.com/llvm/llvm-project/pull/119183