Re: [PATCH v2 1/2] Allow subtarget customization of CC1_SPEC

[Thomas Schwinge <thomas@codesourcery.com>]

Hi!

On 2022-12-07T07:04:10+0100, Sebastian Huber <sebastian.huber@embedded-brains.de> wrote:
> On 06.12.22 22:06, Thomas Schwinge wrote:
> I suppose I just fail to see some detail here, but:
>
>> On 2022-11-21T08:25:25+0100, Sebastian Huber<sebastian.huber@embedded-brains.de>  wrote:
>>> gcc/ChangeLog:
>>>
>>>        * gcc.cc (SUBTARGET_CC1_SPEC): Define if not defined.
>>>        (cc1_spec): Append SUBTARGET_CC1_SPEC.
>>> ---
>>> v2: Append SUBTARGET_CC1_SPEC directly to cc1_spec and not through CC1_SPEC.
>>>      This avoids having to modify all the CC1_SPEC definitions in the targets.
>>>
>>>   gcc/gcc.cc | 9 ++++++++-
>>>   1 file changed, 8 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/gcc/gcc.cc b/gcc/gcc.cc
>>> index 830ab88701f..4e1574a4df1 100644
>>> --- a/gcc/gcc.cc
>>> +++ b/gcc/gcc.cc
>>> @@ -706,6 +706,13 @@ proper position among the other output files.  */
>>>   #define CPP_SPEC ""
>>>   #endif
>>>
>>> +/* Subtargets can define SUBTARGET_CC1_SPEC to provide extra args to cc1 and
>>> +   cc1plus or extra switch-translations.  The SUBTARGET_CC1_SPEC is appended
>>> +   to CC1_SPEC.  */
>>> +#ifndef SUBTARGET_CC1_SPEC
>>> +#define SUBTARGET_CC1_SPEC ""
>>> +#endif
>>> +
>>>   /* config.h can define CC1_SPEC to provide extra args to cc1 and cc1plus
>>>      or extra switch-translations.  */
>>>   #ifndef CC1_SPEC
>>> @@ -1174,7 +1181,7 @@ proper position among the other output files.  */
>>>   static const char *asm_debug = ASM_DEBUG_SPEC;
>>>   static const char *asm_debug_option = ASM_DEBUG_OPTION_SPEC;
>>>   static const char *cpp_spec = CPP_SPEC;
>>> -static const char *cc1_spec = CC1_SPEC;
>>> +static const char *cc1_spec = CC1_SPEC SUBTARGET_CC1_SPEC;
>>>   static const char *cc1plus_spec = CC1PLUS_SPEC;
>>>   static const char *link_gcc_c_sequence_spec = LINK_GCC_C_SEQUENCE_SPEC;
>>>   static const char *link_ssp_spec = LINK_SSP_SPEC;
>>
>> ... doesn't this (at least potentially?) badly interact with any existing
>> 'SUBTARGET_CC1_SPEC' definitions -- which pe rabove get appended to
>> 'cc1_spec'?
>>
>>      gcc/config/loongarch/gnu-user.h-   and provides this hook instead.  */
>>      gcc/config/loongarch/gnu-user.h:#undef SUBTARGET_CC1_SPEC
>>      gcc/config/loongarch/gnu-user.h:#define SUBTARGET_CC1_SPEC GNU_USER_TARGET_CC1_SPEC
>>      gcc/config/loongarch/gnu-user.h-
>>      --
>>      gcc/config/loongarch/loongarch.h-#define EXTRA_SPECS \
>>      gcc/config/loongarch/loongarch.h:  {"subtarget_cc1_spec", SUBTARGET_CC1_SPEC}, \
>>      gcc/config/loongarch/loongarch.h-  {"subtarget_cpp_spec", SUBTARGET_CPP_SPEC}, \
>>      --
>>      gcc/config/mips/gnu-user.h-   and provides this hook instead.  */
>>      gcc/config/mips/gnu-user.h:#undef SUBTARGET_CC1_SPEC
>>      gcc/config/mips/gnu-user.h:#define SUBTARGET_CC1_SPEC GNU_USER_TARGET_CC1_SPEC
>>      gcc/config/mips/gnu-user.h-
>>      --
>>      gcc/config/mips/linux-common.h-
>>      gcc/config/mips/linux-common.h:#undef  SUBTARGET_CC1_SPEC
>>      gcc/config/mips/linux-common.h:#define SUBTARGET_CC1_SPEC                                           \
>>      gcc/config/mips/linux-common.h-  LINUX_OR_ANDROID_CC (GNU_USER_TARGET_CC1_SPEC,                     \
>>      --
>>      gcc/config/mips/mips.h-
>>      gcc/config/mips/mips.h:/* SUBTARGET_CC1_SPEC is passed to the compiler proper.  It may be
>>      gcc/config/mips/mips.h-   overridden by subtargets.  */
>>      gcc/config/mips/mips.h:#ifndef SUBTARGET_CC1_SPEC
>>      gcc/config/mips/mips.h:#define SUBTARGET_CC1_SPEC ""
>>      gcc/config/mips/mips.h-#endif
>>      --
>>      gcc/config/mips/mips.h-#define EXTRA_SPECS                                                  \
>>      gcc/config/mips/mips.h:  { "subtarget_cc1_spec", SUBTARGET_CC1_SPEC },                              \
>>      gcc/config/mips/mips.h-  { "subtarget_cpp_spec", SUBTARGET_CPP_SPEC },                              \
>>      --
>>      gcc/config/mips/r3900.h-/* By default (if not mips-something-else) produce code for the r3900 */
>>      gcc/config/mips/r3900.h:#undef SUBTARGET_CC1_SPEC
>>      gcc/config/mips/r3900.h:#define SUBTARGET_CC1_SPEC "\
>>      gcc/config/mips/r3900.h-%{mhard-float:%e-mhard-float not supported} \
>
> Oh, I came up with the name SUBTARGET_CC1_SPEC after a discussion on the
> mailing list

I've put Iain in CC.

> and I have to admit that I didn't check that it was
> actually already in use.

Always one of the first things I do.  ;-)

> What about renaming the loongarch/mips define
> to LOONGARCH_CC1_SPEC and MIPS_CC1_SPEC?

Also in use are a number of other 'SUBTARGET_[...]_SPEC' and
corresponding 'subtarget_[...]_spec' in 'EXTRA_SPECS', for example:

    gcc/config/mips/mips.h-#define EXTRA_SPECS                                                      \
    gcc/config/mips/mips.h:  { "subtarget_cc1_spec", SUBTARGET_CC1_SPEC },                          \
    gcc/config/mips/mips.h:  { "subtarget_cpp_spec", SUBTARGET_CPP_SPEC },                          \
    gcc/config/mips/mips.h:  { "subtarget_asm_debugging_spec", SUBTARGET_ASM_DEBUGGING_SPEC },      \
    gcc/config/mips/mips.h:  { "subtarget_asm_spec", SUBTARGET_ASM_SPEC },                          \
    gcc/config/mips/mips.h-  { "asm_abi_default_spec", "-" MULTILIB_ABI_DEFAULT },                  \
    gcc/config/mips/mips.h-  { "endian_spec", ENDIAN_SPEC },                                        \
    gcc/config/mips/mips.h:  SUBTARGET_EXTRA_SPECS

Do we need/want to keep the association of same-name
upper-case/lower-case variants; in your proposal you'd then get
'{ "subtarget_cc1_spec", MIPS_CC1_SPEC }', for example?  (I didn't
quickly grok all 'EXTRA_SPECS' usage.)

Alternatively, what about renaming your 'SUBTARGET_CC1_SPEC' to
'CC1_SPEC_EXTRA' -- if that makes sense?

    static const char *cc1_spec = CC1_SPEC CC1_SPEC_EXTRA;

But doesn't somehow this whole thing feel a bit like "chating the
system"?  ;-)

Can't you actually achieve your thing (TLS model) via (new) 'EXTRA_SPECS'
in 'gcc/config/rtems.h', for example?


Grüße
 Thomas
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