[GCC][PATCH v2] arm: Add pacbti related multilib support for armv8.1-m.main.

[Srinath Parvathaneni]

Ping!!
________________________________
From: Gcc-patches <gcc-patches-bounces+srinath.parvathaneni=arm.com@gcc.gnu.org> on behalf of Srinath Parvathaneni via Gcc-patches <gcc-patches@gcc.gnu.org>
Sent: 31 October 2022 15:36
To: gcc-patches@gcc.gnu.org <gcc-patches@gcc.gnu.org>
Cc: Richard Earnshaw <Richard.Earnshaw@arm.com>
Subject: [GCC][PATCH v2] arm: Add pacbti related multilib support for armv8.1-m.main.

Hi,

This patch adds the support for pacbti multlilib linking by making
"-mbranch-protection=none" as default in the command line for all M-profile
targets and uses "-mbranch-protection=none" for multilib matching. If any
valid value is passed to "-mbranch-protection" in the command line, this
new value overwrites the default value in the command line and uses
"-mbranch-protection=standard" for multilib matching.

Eg 1.

If the passed command line flags are:
a) -march=armv8.1-m.main+mve -mfloat-abi=hard -mfpu=auto
b) -mcpu=cortex-m85+nopacbti -mfloat-abi=hard -mfpu=auto

After this patch the command line flags the compiler receives will be:
a) -march=armv8.1-m.main+mve -mfloat-abi=hard -mfpu=auto -mbranch-protection=none
b) -mcpu=cortex-m85+nopacbti -mfloat-abi=hard -mfpu=auto -mbranch-protection=none

"-mbranch-protection=none" will be used in the multilib matching.

Eg 2.

If the passed command line flags are:
a) -march=armv8.1-m.main+mve+pacbti -mfloat-abi=hard -mfpu=auto  -mbranch-protection=pac-ret
b) -mcpu=cortex-m85 -mfloat-abi=hard -mfpu=auto  -mbranch-protection=pac-ret+bti

After this patch the command line flags the compiler receives will be:
a) -march=armv8.1-m.main+mve+pacbti -mfloat-abi=hard -mfpu=auto -mbranch-protection=pac-ret
b) -mcpu=cortex-m85 -mfloat-abi=hard -mfpu=auto -mbranch-protection=pac-ret+bti

"-mbranch-protection=standard" will be used in the multilib matching.

Eg 3.

For A-profile target, if the passed command line flags are:
-march=armv8-a+simd -mfloat-abi=hard -mfpu=auto

Even after this patch the command line flags compiler receives will remain the same:
-march=armv8-a+simd -mfloat-abi=hard -mfpu=auto

Regression tested on arm-none-eabi and bootstrapped on arm-none-linux-gnueabihf.

Ok for master?

Regards,
Srinath.

gcc/ChangeLog:

2022-10-28  Srinath Parvathaneni  <srinath.parvathaneni@arm.com>

        * common/config/arm/arm-common.cc
        (arm_canon_branch_protection_option): Define new function.
        * config/arm/arm-cpus.in (armv8.1-m.main): Move dsp option below pacbti
        option.
        * config/arm/arm.h (arm_canon_branch_protection_option): Define function
        prototype.
        (CANON_BRANCH_PROTECTION_SPEC_FUNCTION): Define macro.
        (MBRANCH_PROTECTION_SPECS): Likewise.
        * config/arm/t-rmprofile (MULTI_ARCH_OPTS_RM): Add new options.
        (MULTI_ARCH_DIRS_RM): Add new directories.
        (MULTILIB_REQUIRED): Add new option.
        (MULTILIB_REUSE): Reuse existing multlibs.
        (MULTILIB_MATCHES): Match multilib strings.

gcc/testsuite/ChangeLog:

2022-10-28  Srinath Parvathaneni  <srinath.parvathaneni@arm.com>

        * gcc.target/arm/multilib.exp (multilib_config "rmprofile"): Update
        tests.
        * gcc.target/arm/pac-10.c: New test.
        * gcc.target/arm/pac-11.c: Likewise.
        * gcc.target/arm/pac-12.c: Likewise.