[clang] [llvm] [HLSL] Add support to branch/flatten attributes to switch (PR #131739)

[via llvm-commits]

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@@ -91,6 +91,137 @@ if.end:                                           ; preds = %if.else, %if.then
   %3 = load i32, ptr %resp, align 4
   ret i32 %3
 }
+
+; CHECK: define i32 @flatten_switch(i32 %X)
+; CHECK-NOT: hlsl.controlflow.hint
+; CHECK:      switch i32 %0, label %sw.epilog [
+; CHECK-NEXT:   i32 0, label %sw.bb
+; CHECK-NEXT:   i32 1, label %sw.bb1
+; CHECK-NEXT:   i32 2, label %sw.bb2
+; CHECK-NEXT: ], !dx.controlflow.hints [[HINT_FLATTEN]]
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joaosaffran wrote:

HINT_FLATTEN will be 2 and HINT_BRANCH will be 1. This is following the same metadata format that DXC uses to represent such hints, https://godbolt.org/z/cnEqbfnbe.

https://github.com/llvm/llvm-project/pull/131739