Re: [GCC][PATCH 13/15, v6] arm: Add support for dwarf debug directives and pseudo hard-register for PAC feature.

[Richard Earnshaw <Richard.Earnshaw@foss.arm.com>]

On 18/01/2023 17:18, Srinath Parvathaneni via Gcc-patches wrote:
> Hello,
> 
> This patch teaches the DWARF support in gcc about RA_AUTH_CODE pseudo hard-register and also
> updates the ".save", ".cfi_register", ".cfi_offset", ".cfi_restore" directives accordingly.
> This patch also adds support to emit ".pacspval" directive when "pac ip, lr, sp" instruction
> in generated in the assembly.
> 
> RA_AUTH_CODE register number is 107 and it's dwarf register number is 143.
> 
> Applying this patch on top of PACBTI series posted here
> https://gcc.gnu.org/pipermail/gcc-patches/2022-August/599658.html and when compiling the following
> test.c with "-march=armv8.1-m.main+mve+pacbti -mbranch-protection=pac-ret -mthumb -mfloat-abi=hard
> fasynchronous-unwind-tables -g -O0 -S" command line options, the assembly output after this patch
> looks like below:
> 
> $cat test.c
> 
> void fun1(int a);
> void fun(int a,...)
> {
>    fun1(a);
> }
> 
> int main()
> {
>    fun (10);
>    return 0;
> }
> 
> $ arm-none-eabi-gcc -march=armv8.1-m.main+mve+pacbti -mbranch-protection=pac-ret -mthumb -mfloat-abi=hard
> -fasynchronous-unwind-tables -g -O0 -S test.s
> 
> Assembly output:
> ...
> fun:
> ...
>          .pacspval
>          pac     ip, lr, sp
>          .cfi_register 143, 12
>          push    {r3, r7, ip, lr}
>          .save {r3, r7, ra_auth_code, lr}
> ...
>          .cfi_offset 143, -24
> ...
>          .cfi_restore 143
> ...
>          aut     ip, lr, sp
>          bx      lr
> ...
> main:
> ...
>          .pacspval
>          pac     ip, lr, sp
>          .cfi_register 143, 12
>          push    {r3, r7, ip, lr}
>          .save {r3, r7, ra_auth_code, lr}
> ...
>          .cfi_offset 143, -8
> ...
>          .cfi_restore 143
> ...
>          aut     ip, lr, sp
>          bx      lr
> ...
> 
> Regression tested on arm-none-eabi target and found no regressions.
> 
> Ok for master?
> 
> Regards,
> Srinath.
> 
> 2023-01-18  Srinath Parvathaneni  <srinath.parvathaneni@arm.com>
> 
>          * config/arm/aout.h (ra_auth_code): Add entry in enum.
>          (emit_multi_reg_push): Add RA_AUTH_CODE register to
>          dwarf frame expression.
>          (arm_emit_multi_reg_pop): Restore RA_AUTH_CODE register.
>          (arm_expand_prologue): Update frame related information and reg notes
>          for pac/pacbit insn.
>          (arm_regno_class): Check for pac pseudo reigster.
>          (arm_dbx_register_number): Assign ra_auth_code register number in dwarf.
>          (arm_init_machine_status): Set pacspval_needed to zero.
>          (arm_debugger_regno): Check for PAC register.
>          (arm_unwind_emit_sequence): Print .save directive with ra_auth_code
>          register.
>          (arm_unwind_emit_set): Add entry for IP_REGNUM in switch case.
>          (arm_unwind_emit): Update REG_CFA_REGISTER case._
>          * config/arm/arm.h (FIRST_PSEUDO_REGISTER): Modify.
>          (DWARF_PAC_REGNUM): Define.
>          (IS_PAC_REGNUM): Likewise.
>          (enum reg_class): Add PAC_REG entry.
>          (machine_function): Add pacbti_needed state to structure.
>          * config/arm/arm.md (RA_AUTH_CODE): Define.
> 
> gcc/testsuite/ChangeLog:
> 
> 2023-01-18  Srinath Parvathaneni  <srinath.parvathaneni@arm.com>
> 
>          * g++.target/arm/pac-1.C: New test.
>          * gcc.target/arm/pac-15.c: Likewise.

OK.

R.