[llvm] [AMDGPU][GlobalISel] Add buffer store byte/short RegBankLegalize rules (PR #179367)

[Matt Arsenault via llvm-commits]

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@@ -1275,6 +1325,14 @@ define <4 x ptr addrspace(5)> @load_v4p5(ptr addrspace(8) inreg %buf) {
 ; GISEL-NEXT:    s_waitcnt vmcnt(0) expcnt(0) lgkmcnt(0)
 ; GISEL-NEXT:    buffer_load_dwordx4 v[0:3], off, s[16:19], 0
 ; GISEL-NEXT:    s_waitcnt vmcnt(0)
+; GISEL-NEXT:    v_readfirstlane_b32 s4, v0
+; GISEL-NEXT:    v_readfirstlane_b32 s5, v1
+; GISEL-NEXT:    v_readfirstlane_b32 s6, v2
+; GISEL-NEXT:    v_readfirstlane_b32 s7, v3
+; GISEL-NEXT:    v_mov_b32_e32 v0, s4
+; GISEL-NEXT:    v_mov_b32_e32 v1, s5
+; GISEL-NEXT:    v_mov_b32_e32 v2, s6
+; GISEL-NEXT:    v_mov_b32_e32 v3, s7
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arsenm wrote:

Ugly regression 

https://github.com/llvm/llvm-project/pull/179367