[clang] [PAC] Do not support some values of branch-protection with ptrauth-returns (PR #125280)

[Daniel Kiss via cfe-commits]

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@@ -0,0 +1,28 @@
+// REQUIRES: aarch64-registered-target
+
+// RUN: %clang -target aarch64-linux-pauthtest   %s -S -emit-llvm -o - 2>&1 | FileCheck --implicit-check-not=warning: %s
+// RUN: %clang -target aarch64 -fptrauth-returns %s -S -emit-llvm -o - 2>&1 | FileCheck --implicit-check-not=warning: %s
+
+/// Unsupported with pauthtest, warning emitted
+__attribute__((target("branch-protection=pac-ret"))) void f1() {}
+// CHECK:      warning: unsupported 'branch-protection' in the 'target' attribute string; 'target' attribute ignored [-Wignored-attributes]
+// CHECK-NEXT: __attribute__((target("branch-protection=pac-ret"))) void f1() {}
+__attribute__((target("branch-protection=gcs"))) void f2() {}
+// CHECK:      warning: unsupported 'branch-protection' in the 'target' attribute string; 'target' attribute ignored [-Wignored-attributes]
+// CHECK-NEXT: __attribute__((target("branch-protection=gcs"))) void f2() {}
+__attribute__((target("branch-protection=standard"))) void f3() {}
+// CHECK:      warning: unsupported 'branch-protection' in the 'target' attribute string; 'target' attribute ignored [-Wignored-attributes]
+// CHECK-NEXT: __attribute__((target("branch-protection=standard"))) void f3() {}
+
+/// Supported with pauthtest, no warning emitted
+__attribute__((target("branch-protection=bti"))) void f4() {}
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DanielKristofKiss wrote:

I'd add a test case of the "branch-protection=none". 

https://github.com/llvm/llvm-project/pull/125280