[PATCH v2] arm: Fix missing bti instruction for virtual thunks

[Richard Ball <richard.ball@arm.com>]

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v2: Formatting and test options fix.

Adds missing bti instruction at the beginning of a virtual
thunk, when bti is enabled.

gcc/ChangeLog:

	* config/arm/arm.cc (arm_output_mi_thunk): Emit
	insn for bti_c when bti is enabled.

gcc/testsuite/ChangeLog:

        * lib/target-supports.exp: Add v8_1_m_main_pacbti.
        * g++.target/arm/bti_thunk.C: New test.

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diff --git a/gcc/config/arm/arm.cc b/gcc/config/arm/arm.cc
index e5a944486d7bd583627b0e22dfe8f95862e975bb..c44047c377a802d0c1dc1406df1b88a6b079607b 100644
--- a/gcc/config/arm/arm.cc
+++ b/gcc/config/arm/arm.cc
@@ -29257,6 +29257,8 @@ arm_output_mi_thunk (FILE *file, tree thunk, HOST_WIDE_INT delta,
   const char *fnname = IDENTIFIER_POINTER (DECL_ASSEMBLER_NAME (thunk));
 
   assemble_start_function (thunk, fnname);
+  if (aarch_bti_enabled ())
+    emit_insn (aarch_gen_bti_c ());
   if (TARGET_32BIT)
     arm32_output_mi_thunk (file, thunk, delta, vcall_offset, function);
   else
diff --git a/gcc/testsuite/g++.target/arm/bti_thunk.C b/gcc/testsuite/g++.target/arm/bti_thunk.C
new file mode 100644
index 0000000000000000000000000000000000000000..23c1acc66629ba5907830ae27de0b29a47032c65
--- /dev/null
+++ b/gcc/testsuite/g++.target/arm/bti_thunk.C
@@ -0,0 +1,20 @@
+/* { dg-do compile } */
+/* { dg-require-effective-target arm_arch_v8_1m_main_pacbti_ok } */
+/* { dg-add-options arm_arch_v8_1m_main_pacbti } */
+/* { dg-additional-options "-mbranch-protection=bti" }*/
+
+#include <stdio.h>
+
+struct C18 {
+  virtual void f7();
+};
+
+struct C19 : virtual C18 {
+  virtual void f7();
+};
+
+void C19::f7() {
+  printf("foo\n");
+}
+
+/* { dg-final { scan-assembler-times "\tbti" 2 } } */
diff --git a/gcc/testsuite/lib/target-supports.exp b/gcc/testsuite/lib/target-supports.exp
index 73360cd3a0d5553ff7586b48e0bb17298e6612f0..3070b51b9b86e1a2bad630a765a075f8b911d2ad 100644
--- a/gcc/testsuite/lib/target-supports.exp
+++ b/gcc/testsuite/lib/target-supports.exp
@@ -5524,6 +5524,8 @@ foreach { armfunc armflag armdefs } {
 		__ARM_ARCH_8M_BASE__
 	v8m_main "-march=armv8-m.main+fp -mthumb" __ARM_ARCH_8M_MAIN__
 	v8_1m_main "-march=armv8.1-m.main+fp -mthumb" __ARM_ARCH_8M_MAIN__
+	v8_1m_main_pacbti "-march=armv8.1-m.main+pacbti+fp -mthumb"
+		"__ARM_ARCH_8M_MAIN__ && __ARM_FEATURE_BTI"
 	v9a "-march=armv9-a+simd" __ARM_ARCH_9A__ } {
     eval [string map [list FUNC $armfunc FLAG $armflag DEFS $armdefs ] {
 	proc check_effective_target_arm_arch_FUNC_ok { } {