[PATCH][GCC][AARCH64] Add effective-target check to b key execution tests

[Sam Tebbs]

Hi all,

This patch adds an effective target check to the pointer authentication B key 
execution tests. These were failing with an assembler error when run with a 
non-recent version of binutils, and this change will instead make them 
unsupported in such cases.

Tested with a recent version of binutils where it passes, and with a non-recent 
version where it is unsupported.

OK for trunk?

Sam

gcc/testsuite
2019-08-02  Sam Tebbs<sam.te...@arm.com>

        * lib/target-supports.exp
        (check_effective_target_arm_v8_4a_bkey_directive): New proc.
        * g++.target/aarch64/return_address_sign_b_exception.C,
        return_address_sign_ab_exception.C: Add dg-require-effective-target
        checks.


diff --git 
a/gcc/testsuite/g++.target/aarch64/return_address_sign_ab_exception.C 
b/gcc/testsuite/g++.target/aarch64/return_address_sign_ab_exception.C
index 520cd18..ead11de 100644
--- a/gcc/testsuite/g++.target/aarch64/return_address_sign_ab_exception.C
+++ b/gcc/testsuite/g++.target/aarch64/return_address_sign_ab_exception.C
@@ -1,5 +1,6 @@
 /* { dg-do run } */
 /* { dg-options "--save-temps" } */
+/* { dg-require-effective-target arm_v8_3a_bkey_directive } */
 
 __attribute__((target("branch-protection=pac-ret+leaf")))
 int foo_a () {
diff --git a/gcc/testsuite/g++.target/aarch64/return_address_sign_b_exception.C 
b/gcc/testsuite/g++.target/aarch64/return_address_sign_b_exception.C
index eab2869..2f82731 100644
--- a/gcc/testsuite/g++.target/aarch64/return_address_sign_b_exception.C
+++ b/gcc/testsuite/g++.target/aarch64/return_address_sign_b_exception.C
@@ -1,5 +1,6 @@
 /* { dg-do run } */
 /* { dg-options "-mbranch-protection=pac-ret+leaf+b-key --save-temps" } */
+/* { dg-require-effective-target arm_v8_3a_bkey_directive } */
 
 int foo () {
   throw 22;
diff --git a/gcc/testsuite/lib/target-supports.exp 
b/gcc/testsuite/lib/target-supports.exp
index 815e837..3c50b89 100644
--- a/gcc/testsuite/lib/target-supports.exp
+++ b/gcc/testsuite/lib/target-supports.exp
@@ -9463,6 +9463,16 @@ proc check_effective_target_arm_v8_3a_complex_neon_hw { 
} {
     } [add_options_for_arm_v8_3a_complex_neon ""]]
 }
 
+# Return 1 if the assembler supports assembling the Armv8.3 pointer 
authentication B key directive
+proc check_effective_target_arm_v8_3a_bkey_directive { } {
+       return [check_no_compiler_messages cet object {
+               int main(void) {
+                       asm (".cfi_b_key_frame");
+                       return 0;
+               }
+       }]
+}
+
 # Returns 1 if the target is using glibc, 0 otherwise.
 
 proc check_effective_target_glibc { } {