[llvm] [AMDGPU] Mark S_NOP as having side effects (PR #65745)

[Jay Foad via llvm-commits]

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@@ -343,9 +343,41 @@ body:             |
   ; GCN: bb.0:
   ; GCN-NEXT:   successors: %bb.1(0x80000000)
   ; GCN-NEXT: {{  $}}
+  ; GCN-NEXT:   S_NOP 0
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jayfoad wrote:

S_NOPs are no longer deleted by dead-mi-elimination.

https://github.com/llvm/llvm-project/pull/65745