[clang] [clang][TableGen] Fix Duplicate Entries in TableGen (PR #140828)

[Aaron Ballman via cfe-commits]

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@@ -0,0 +1,12 @@
+// RUN: %clang_cc1 -triple riscv64 -ast-dump -ast-dump-filter c23 -std=c23 -x c %s | FileCheck --strict-whitespace %s
+
+// CHECK:       FunctionDecl{{.*}}pre_c23
+// CHECK-NEXT:    |-CompoundStmt
+// CHECK-NEXT:    `-RISCVInterruptAttr{{.*}}supervisor
+__attribute__((interrupt("supervisor"))) void pre_c23(){}
+
+// CHECK:       FunctionDecl{{.*}}in_c23
+// CHECK-NEXT:    |-CompoundStmt
+// CHECK-NEXT:    `-RISCVInterruptAttr{{.*}}supervisor
+// CHECK-NOT:     `-RISCVInterruptAttr{{.*}}machine
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AaronBallman wrote:

Before this patch, our "has attribute" check was looking through a `StringSwitch` that had multiple cases with the same string argument but different resulting values (that would check for target triples and arches). So we'd hit the first case, say "this matches", and the test for the attribute would only pass if the target triple matched. Because the first triple was never the RISCV attribute, we'd always say "we don't have this attribute". In turn, this would mean parsing would say "well, we don't know about this attribute, so eat all the arguments". But because Sema could figure out which `handleInterruptAttr` function to call, we'd actually go ahead and make the correct attribute, just with the incorrect argument. The default if no argument is specified for RISCV is `machine`. So we'd ignore `supervisor` and just substitute in `machine` quietly for the user.

https://github.com/llvm/llvm-project/pull/140828