[llvm] [RFC][InstCombine] Combine fence with target specific sync scope (PR #93939)

[Pierre van Houtryve via llvm-commits]

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@@ -30,6 +30,15 @@ define void @test_target_dependent_scope() {
   ret void
 }
 
+; CHECK-LABEL: combine_target_dependent_scope
+; CHECK-NEXT: fence syncscope("agent") seq_cst
+; CHECK-NEXT: ret void
+define void @combine_target_dependent_scope() {
+  fence syncscope("agent") acq_rel
+  fence syncscope("agent") seq_cst
+  ret void
+}
+
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Pierre-vh wrote:

I don't think it is combined here, we'd need to call `MMRAMetadata::combine` or `combineMetadata` from Local.h

https://github.com/llvm/llvm-project/pull/93939