[gcc r14-9022] Arm: Fix incorrect tailcall-generation for indirect calls [PR113780]

[Tejas Belagod <belagod@gcc.gnu.org>]

https://gcc.gnu.org/g:f436a2ab6ad15968275c9bbf3bd56647e5559e68

commit r14-9022-gf436a2ab6ad15968275c9bbf3bd56647e5559e68
Author: Tejas Belagod <tejas.belagod@arm.com>
Date:   Thu Jan 25 16:05:36 2024 +0530

    Arm: Fix incorrect tailcall-generation for indirect calls [PR113780]
    
    This patch fixes a bug that causes indirect calls in PAC-enabled functions
    to be tailcalled incorrectly when all argument registers R0-R3 are used.
    
    2024-02-07  Tejas Belagod  <tejas.belagod@arm.com>
    
            PR target/113780
            * config/arm/arm.cc (arm_function_ok_for_sibcall): Don't allow tailcalls
            for indirect calls with 4 or more arguments in pac-enabled functions.
    
            * lib/target-supports.exp (v8_1m_main_pacbti): Add __ARM_FEATURE_PAUTH.
            * gcc.target/arm/pac-sibcall.c: New.

Diff:
---
 gcc/config/arm/arm.cc                      | 11 +++++++----
 gcc/testsuite/gcc.target/arm/pac-sibcall.c | 14 ++++++++++++++
 gcc/testsuite/lib/target-supports.exp      |  2 +-
 3 files changed, 22 insertions(+), 5 deletions(-)

diff --git a/gcc/config/arm/arm.cc b/gcc/config/arm/arm.cc
index c44047c377a8..1cd69268ee98 100644
--- a/gcc/config/arm/arm.cc
+++ b/gcc/config/arm/arm.cc
@@ -7980,10 +7980,13 @@ arm_function_ok_for_sibcall (tree decl, tree exp)
       && DECL_WEAK (decl))
     return false;
 
-  /* We cannot do a tailcall for an indirect call by descriptor if all the
-     argument registers are used because the only register left to load the
-     address is IP and it will already contain the static chain.  */
-  if (!decl && CALL_EXPR_BY_DESCRIPTOR (exp) && !flag_trampolines)
+  /* We cannot tailcall an indirect call by descriptor if all the call-clobbered
+     general registers are live (r0-r3 and ip).  This can happen when:
+      - IP contains the static chain, or
+      - IP is needed for validating the PAC signature.  */
+  if (!decl
+      && ((CALL_EXPR_BY_DESCRIPTOR (exp) && !flag_trampolines)
+	  || arm_current_function_pac_enabled_p()))
     {
       tree fntype = TREE_TYPE (TREE_TYPE (CALL_EXPR_FN (exp)));
       CUMULATIVE_ARGS cum;
diff --git a/gcc/testsuite/gcc.target/arm/pac-sibcall.c b/gcc/testsuite/gcc.target/arm/pac-sibcall.c
new file mode 100644
index 000000000000..e15bd2f478d1
--- /dev/null
+++ b/gcc/testsuite/gcc.target/arm/pac-sibcall.c
@@ -0,0 +1,14 @@
+/* If all call-clobbered general registers are live (r0-r3, ip), disable
+   indirect tail-call for a PAC-enabled function.  */
+
+/* { 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=pac-ret+leaf -O2" } */
+
+void fail(void (*f)(int, int, int, int))
+{
+  f(1, 2, 3, 4);
+}
+
+/* { dg-final { scan-assembler-not "bx\tip\t@ indirect register sibling call" } } */
diff --git a/gcc/testsuite/lib/target-supports.exp b/gcc/testsuite/lib/target-supports.exp
index 81715999f871..645759496b7b 100644
--- a/gcc/testsuite/lib/target-supports.exp
+++ b/gcc/testsuite/lib/target-supports.exp
@@ -5534,7 +5534,7 @@ foreach { armfunc armflag armdefs } {
 	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"
+		"__ARM_ARCH_8M_MAIN__ && __ARM_FEATURE_BTI && __ARM_FEATURE_PAUTH"
 	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 { } {