[llvm] [AMDGPU] Unused sdst writing to null (PR #133229)

[Ana Mihajlovic via llvm-commits]

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@@ -39,7 +39,8 @@ define amdgpu_ps void @v_add_u64(ptr addrspace(1) %out, i64 %a, i64 %b) {
 ; GCN-LABEL: v_add_u64:
 ; GCN:       ; %bb.0: ; %entry
 ; GCN-NEXT:    v_add_co_u32 v2, vcc_lo, v2, v4
-; GCN-NEXT:    v_add_co_ci_u32_e32 v3, vcc_lo, v3, v5, vcc_lo
+; GCN-NEXT:    s_delay_alu instid0(VALU_DEP_1)
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mihajlovicana wrote:

Delay alu pass skips implicit def operators (suppose that should be done since it's marked with TODO). 

VOP2:
`renamable $vgpr13 = V_ADDC_U32_e32 0, killed $vgpr13, implicit-def dead $vcc_lo, implicit killed $vcc_lo, implicit $exec`

VOP3:
`renamable $vgpr13, dead $sgpr_null = V_ADDC_U32_e64 0, killed $vgpr13, killed $vcc_lo, 0, implicit $exec`

In VOP2, vcc is implicit so delay alu will not consider it, but as I understood the correct behaviour would be for delay_alu to be in both?

https://github.com/llvm/llvm-project/pull/133229