Re: [PATCHv2, PING 3][ARM] -mpure-code option for ARM

["Andre Vieira (lists)" <Andre.SimoesDiasVieira@arm.com>]

On 11/08/16 15:13, Andre Vieira (lists) wrote:
> On 25/07/16 11:52, Andre Vieira (lists) wrote:
>> 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.
>>
> Ping
> 

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