[llvm] [AMDGPU] Reland "Remove redundant s_cmp_lg_* sX, 0" (PR #164201)

[Matt Arsenault via llvm-commits]

================
@@ -599,7 +599,7 @@ define amdgpu_ps i32 @not64(i64 inreg %val0) {
 ; Negative tests
 ; --------------------------------------------------------------------------------
 
- at 1 = external dso_local addrspace(4) constant i32
+ at 1 = weak dso_local addrspace(4) constant i32 zeroinitializer
----------------
arsenm wrote:

```suggestion
@1 = extern_weak dso_local addrspace(4) constant i32
```

https://github.com/llvm/llvm-project/pull/164201