[PATCH 4/12] arm: Add testsuite library support for PACBTI target

[Andrea Corallo via Gcc-patches]

Add targeting-checking entities for PACBTI in testsuite
framework.

Pre-approved with the requested changes here
<https://gcc.gnu.org/pipermail/gcc-patches/2021-December/586331.html>.

gcc/testsuite/ChangeLog:

        * testsuite/lib/target-supports.exp:
        (check_effective_target_arm_pacbti_hw): New.
        * doc/sourcebuild.texi: Document arm_pacbti_hw.

Co-Authored-By: Tejas Belagod  <tbela...@arm.com>


diff --git a/gcc/doc/sourcebuild.texi b/gcc/doc/sourcebuild.texi
index 613ac29967b..e8cbd8e4aef 100644
--- a/gcc/doc/sourcebuild.texi
+++ b/gcc/doc/sourcebuild.texi
@@ -2167,6 +2167,10 @@ ARM target supports options to generate instructions 
from ARMv8.1-M with
 the Custom Datapath Extension (CDE) and M-Profile Vector Extension (MVE).
 Some multilibs may be incompatible with these options.
 
+@item arm_pacbti_hw
+Test system supports executing Pointer Authentication and Branch Target
+Identification instructions.
+
 @item arm_prefer_ldrd_strd
 ARM target prefers @code{LDRD} and @code{STRD} instructions over
 @code{LDM} and @code{STM} instructions.
diff --git a/gcc/testsuite/lib/target-supports.exp 
b/gcc/testsuite/lib/target-supports.exp
index ff8edbd3e17..df8ab037fb3 100644
--- a/gcc/testsuite/lib/target-supports.exp
+++ b/gcc/testsuite/lib/target-supports.exp
@@ -5090,6 +5090,22 @@ proc check_effective_target_arm_cmse_clear_ok {} {
     } "-mcmse"];
 }
 
+# Return 1 if the target supports executing PACBTI instructions, 0
+# otherwise.
+
+proc check_effective_target_arm_pacbti_hw {} {
+    return [check_runtime arm_pacbti_hw_available {
+       __attribute__ ((naked)) int
+       main (void)
+       {
+         asm ("pac r12, lr, sp");
+         asm ("mov r0, #0");
+         asm ("autg r12, lr, sp");
+         asm ("bx lr");
+       }
+    } ""]
+}
+
 # Return 1 if this compilation turns on string_ops_prefer_neon on.
 
 proc check_effective_target_arm_tune_string_ops_prefer_neon { } {