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

[Sebastian Huber <sebastian.huber@embedded-brains.de>]

On 07.12.22 08:10, Thomas Schwinge wrote:
> 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;

I was told that an operating system is the subtarget in this context. So 
from the name SUBTARGET_CC1_SPEC is is clear who is in charge. This is 
not clear from 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?

The EXTRA_SPECS definition seems to be target-specific. Not all targets 
let an operating system define SUBTARGET_EXTRA_SPECS. The 
SUBTARGET_EXTRA_SPECS would need to get propagated to the corresponding 
specs, which seems to be also target-specific, for example for mips we have:

#undef CC1_SPEC
#define CC1_SPEC "\
%{G*} %{EB:-meb} %{EL:-mel} %{EB:%{EL:%emay not use both -EB and -EL}} \
%(subtarget_cc1_spec)"

I think going this route would lead to a lot of changes affecting all 
targets.

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