[llvm] Fix for revert of dea5aa73f (PR #134153)

[Matt Arsenault via llvm-commits]

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@@ -806,7 +808,9 @@ define double @optnone_atomicrmw_fadd_f64_expand(double %val) #1 {
 ; GFX90A-NEXT:    v_cndmask_b32_e64 v2, 0, 1, s[4:5]
 ; GFX90A-NEXT:    s_mov_b64 s[4:5], -1
 ; GFX90A-NEXT:    s_mov_b32 s6, 1
-; GFX90A-NEXT:    v_cmp_ne_u32_e64 s[6:7], v2, s6
+; GFX90A-NEXT:    v_readfirstlane_b32 s7, v2
+; GFX90A-NEXT:    s_cmp_lg_u32 s7, s6
+; GFX90A-NEXT:    s_cselect_b64 s[6:7], -1, 0
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arsenm wrote:

This is worse 

https://github.com/llvm/llvm-project/pull/134153