[llvm] [AMDGPU][GlobalISel] Add register bank legalization for G_SMIN/G_SMAX/G_UMIN/G_UMAX (PR #159821)

[Matt Arsenault via llvm-commits]

================
@@ -2159,7 +2159,7 @@ define i16 @test_vector_reduce_smax_v8i16(<8 x i16> %v) {
 ; GFX10-GISEL-NEXT:    v_pk_max_i16 v0, v0, v2
 ; GFX10-GISEL-NEXT:    v_pk_max_i16 v1, v1, v3
 ; GFX10-GISEL-NEXT:    v_pk_max_i16 v0, v0, v1
-; GFX10-GISEL-NEXT:    v_lshrrev_b32_e32 v1, 16, v0
+; GFX10-GISEL-NEXT:    v_alignbit_b32 v1, s4, v0, 16
----------------
arsenm wrote:

This is a regression

https://github.com/llvm/llvm-project/pull/159821