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[PATCHv2, PING][ARM] -mpure-code option for ARM


On 11/07/16 17:56, Andre Vieira (lists) wrote:
> On 07/07/16 13:30, mickael guene wrote:
>> Hi Andre,
>>
>>  Another feedback on your purecode patch.
>>  You have to disable casesi pattern since then it will
>> generate wrong code with -mpure-code option.
>>  Indeed it will generate an 'adr rx, .Lx' (aka
>> 'subs rx, PC, #offset') which will not work in our
>> case since 'Lx' label is put in an .rodata section.
>> So offset value is unknown and can be impossible
>> to encode correctly.
>>
>> Regards
>> Mickael
>>
>> On 06/30/2016 04:32 PM, Andre Vieira (lists) wrote:
>>> Hello,
>>>
>>> This patch adds the -mpure-code option for ARM. This option ensures
>>> functions are put into sections that contain only code and no data. To
>>> ensure this throughout compilation we give these sections the ARM
>>> processor-specific ELF section attribute "SHF_ARM_PURECODE". This option
>>> is only supported for non-pic code for armv7-m targets.
>>>
>>> This patch introduces a new target hook 'TARGET_ASM_ELF_FLAGS_NUMERIC'.
>>> This target hook enables a target to use the numeric value for elf
>>> section attributes rather than their alphabetical representation. If
>>> TARGET_ASM_ELF_FLAGS_NUMERIC returns TRUE, the existing
>>> 'default_elf_asm_named_section', will print the numeric value of the
>>> section attributes for the current section. This target hook has two
>>> parameters:
>>> unsigned int FLAGS, the input parameter that tells the function the
>>> current section's attributes;
>>> unsigned int *NUM, used to pass down the numerical representation of the
>>> section's attributes.
>>>
>>> The default implementation for TARGET_ASM_ELF_FLAGS_NUMERIC will return
>>> false, so existing behavior is not changed.
>>>
>>> Bootstrapped and tested for arm-none-linux-gnueabihf. Further tested for
>>> arm-none-eabi with a Cortex-M3 target.
>>>
>>>
>>> gcc/ChangeLog:
>>> 2016-06-30  Andre Vieira  <andre.simoesdiasvieira@arm.com>
>>>             Terry Guo  <terry.guo@arm.com>
>>>
>>>         * target.def (elf_flags_numeric): New target hook.
>>>         * targhooks.h (default_asm_elf_flags_numeric): New.
>>>         * varasm.c (default_asm_elf_flags_numeric): New.
>>>           (default_elf_asm_named_section): Use new target hook.
>>>         * config/arm/arm.opt (mpure-code): New.
>>>         * config/arm/arm.h (SECTION_ARM_PURECODE): New.
>>>         * config/arm/arm.c (arm_asm_init_sections): Add section
>>>           attribute to default text section if -mpure-code.
>>>           (arm_option_check_internal): Diagnose use of option with
>>>           non supported targets and/or options.
>>>           (arm_asm_elf_flags_numeric): New.
>>>           (arm_function_section): New.
>>>           (arm_elf_section_type_flags): New.
>>>         * config/arm/elf.h (JUMP_TABLES_IN_TEXT_SECTION): Disable
>>>           for -mpure-code.
>>>         * gcc/doc/texi (TARGET_ASM_ELF_FLAGS_NUMERIC): New.
>>>         * gcc/doc/texi.in (TARGET_ASM_ELF_FLAGS_NUMERIC): Likewise.
>>>
>>>
>>>
>>> gcc/testsuite/ChangeLog:
>>> 2016-06-30  Andre Vieira  <andre.simoesdiasvieira@arm.com>
>>>             Terry Guo  <terry.guo@arm.com>
>>>
>>>         * gcc.target/arm/pure-code/ffunction-sections.c: New.
>>>         * gcc.target/arm/pure-code/no-literal-pool.c: New.
>>>         * gcc.target/arm/pure-code/pure-code.exp: New.
>>>
>>
> Hi Sandra, Mickael,
> 
> Thank you for your comments. I changed the description of -mpure-code in
> invoke.texi to better reflect the error message you get wrt supported
> targets.
> 
> As for the target hook description, I hope the text is clearer now. Let
> me know if you think it needs further explanation.
> 
> I also fixed the double '%' in the text string for unnamed text sections
> and disabled the casesi pattern.
> 
> I duplicated the original casesi test
> 'gcc/testsuite/gcc.c-torture/compile/pr46934.c' for pure-code to make
> sure the casesi was disabled and other patterns were selected instead.
> 
> Reran regressions for pure-code.exp for Cortex-M3.
> 
> Cheers,
> Andre
> 
> 
> gcc/ChangeLog:
> 2016-07-11  Andre Vieira  <andre.simoesdiasvieira@arm.com>
>             Terry Guo  <terry.guo@arm.com>
> 
>         * target.def (elf_flags_numeric): New target hook.
>         * hooks.c (hook_uint_uintp_false): New generic hook.
>         * varasm.c (default_elf_asm_named_section): Use new target hook.
>         * config/arm/arm.opt (mpure-code): New.
>         * config/arm/arm.h (SECTION_ARM_PURECODE): New.
>         * config/arm/arm.c (arm_asm_init_sections): Add section
>         attribute to default text section if -mpure-code.
>         (arm_option_check_internal): Diagnose use of option with
>         non supported targets and/or options.
>         (arm_asm_elf_flags_numeric): New.
>         (arm_function_section): New.
>         (arm_elf_section_type_flags): New.
>         * config/arm/elf.h (JUMP_TABLES_IN_TEXT_SECTION): Disable
>         for -mpure-code.
>         * config/arm/arm.md (casesi): Disable pattern for
>         -mpure-code.
>         * gcc/doc/texi (TARGET_ASM_ELF_FLAGS_NUMERIC): New.
>         * gcc/doc/texi.in (TARGET_ASM_ELF_FLAGS_NUMERIC): Likewise.
> 
> 
> 
> gcc/testsuite/ChangeLog:
> 2016-07-11  Andre Vieira  <andre.simoesdiasvieira@arm.com>
>             Terry Guo  <terry.guo@arm.com>
> 
>         * gcc.target/arm/pure-code/ffunction-sections.c: New.
>         * gcc.target/arm/pure-code/no-literal-pool.c: New.
>         * gcc.target/arm/pure-code/no-casesi.c: New.
>         * gcc.target/arm/pure-code/pure-code.exp: New.
> 
Ping.


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