Re: [PATCH] fortran: Enable target preprocessor macros with -cpp [PR42954]

Hi Chris, all,

as there have been no further comments, and since trunk is open
after 16-release, I will commit the patch as-is.

Thanks,
Harald

Am 17.04.26 um 10:10 PM schrieb Harald Anlauf:
> Hi Chris,
> 
> thanks for attacking this!
> 
> I briefly tested this.
> 
> Am 16.04.26 um 7:16 PM schrieb Christopher Albert:
>> The Fortran preprocessor has never defined target-specific macros such as
>> __linux__, __unix__, __ELF__, __x86_64__, or __amd64__ that the C
>> preprocessor provides.  This was caused by the TARGET_OS_CPP_BUILTINS,
>> TARGET_OBJFMT_CPP_BUILTINS, and TARGET_CPU_CPP_BUILTINS hooks being
>> disabled since 2008 (marked as "Pandora's Box") because several target
>> config headers use C-family-only functions.
>>
>> Fix by providing Fortran-compatible local helpers for
>> builtin_define_std, builtin_define_with_value, and
>> builtin_define_with_int_value (which in the C frontend live in
>> c-family/c-cppbuiltin.cc and use the C-family-only globals parse_in
>> and flag_iso), plus wrapper macros for c_dialect_cxx, flag_iso, and
>> other C-family identifiers referenced by target config headers.  This
>> allows TARGET_OS_CPP_BUILTINS and TARGET_OBJFMT_CPP_BUILTINS to
>> execute in the Fortran frontend.
>>
>> Unlike the C frontend default (flag_iso=0, GNU extensions mode), the
>> Fortran wrapper sets flag_iso=1 to suppress user-namespace macros like
>> bare "unix" and "linux" that would conflict with Fortran identifiers.
>> Only the reserved-namespace forms (__unix__, __linux__, etc.) are
>> defined.  Fortran has no -std=cNN equivalent to control this, so the
>> conservative choice avoids silent identifier replacement.
>>
>> For TARGET_CPU_CPP_BUILTINS, which on most architectures expands to a
>> function in a C-family-only object file (e.g., ix86_target_macros in
>> i386-c.cc), provide an x86 implementation directly in fortran/cpp.cc
>> that covers architecture identification and float-size macros.
>> ISA feature macros (__SSE__, __AVX__, etc.) are not included; if
>> needed, they could be factored out of i386-c.cc into a shared object.
> 
> I noticed that the latter are missing.  Can you estimate how much
> work it would be to also provide the essential ISA feature macros?
> (__AVX__/__AVX2__/... are likely more important than the __SSE*__
> counterparts; maybe the __FMA__ family might be of interest.
> I also consider the other arch/tune settings less important.)
> 
> Otherwise it looks good to me so far, and we should get this into
> mainline early in stage 1.
> 
> Can anybody else test this on a non-linux or non-x86 platform?
> 
> Thanks,
> Harald
> 
>> Remove the dead __attribute__((target(...))) block from
>> gfortran.dg/gomp/declare-variant-10.f90: it was guarded by
>> #if defined(__x86_64__) which was previously always false because
>> gfortran never defined these macros, and gfortran does not support
>> C-style __attribute__ syntax.
>>
>> Co-authored-by: Kai Tietz <[email protected]>
>>
>>     PR fortran/42954
>>
>> gcc/fortran/ChangeLog:
>>
>>     * cpp.cc (gfc_builtin_define_std): New helper mirroring
>>     builtin_define_std from c-family/c-cppbuiltin.cc.
>>     (gfc_builtin_define_with_value): New helper mirroring
>>     builtin_define_with_value from c-family/c-cppbuiltin.cc.
>>     (gfc_define_ix86_target_macros): New function providing x86 CPU
>>     identification macros for the Fortran preprocessor.
>>     (gfc_darwin_cpp_builtins): New function providing Darwin platform
>>     macros.
>>     (cpp_define_builtins): Remove Pandora's Box FIXME.  Add wrapper
>>     macros for C-family functions and variables used in target config
>>     headers.  Set flag_iso=1 to suppress bare-name macros.  Enable
>>     TARGET_OS_CPP_BUILTINS and TARGET_OBJFMT_CPP_BUILTINS.  Call
>>     gfc_define_ix86_target_macros on x86 targets.
>>
>> gcc/testsuite/ChangeLog:
>>
>>     * gfortran.dg/gomp/declare-variant-10.f90: Remove dead
>>     __attribute__((target)) block that is now exposed by newly
>>     defined target macros.
>>     * gfortran.dg/pr42954-linux.f90: New test.
>>     * gfortran.dg/pr42954-x86.f90: New test.
>>
>> Signed-off-by: Christopher Albert <[email protected]>
>> ---
>>   gcc/fortran/cpp.cc                            | 178 ++++++++++++++++--
>>   .../gfortran.dg/gomp/declare-variant-10.f90   |   3 -
>>   gcc/testsuite/gfortran.dg/pr42954-linux.f90   |  24 +++
>>   gcc/testsuite/gfortran.dg/pr42954-x86.f90     |  10 +
>>   4 files changed, 194 insertions(+), 21 deletions(-)
>>   create mode 100644 gcc/testsuite/gfortran.dg/pr42954-linux.f90
>>   create mode 100644 gcc/testsuite/gfortran.dg/pr42954-x86.f90
>>
>> diff --git a/gcc/fortran/cpp.cc b/gcc/fortran/cpp.cc
>> index 6b5f136e4f3..ada1bc1a211 100644
>> --- a/gcc/fortran/cpp.cc
>> +++ b/gcc/fortran/cpp.cc
>> @@ -157,6 +157,126 @@ void pp_dir_change (cpp_reader *, const char *);
>>   static int dump_macro (cpp_reader *, cpp_hashnode *, void *);
>>   static void dump_queued_macros (cpp_reader *);
>> +/* Fortran-local helpers that mirror builtin_define_std,
>> +   builtin_define_with_value, and builtin_define_with_int_value from
>> +   c-family/c-cppbuiltin.cc.  Those functions use the C-family-only
>> +   globals parse_in and flag_iso, so they cannot be called directly
>> +   from the Fortran frontend.  */
>> +
>> +/* Given "unix", define __unix, __unix__, and (if DEFINE_USER) unix.  */
>> +
>> +static void
>> +gfc_builtin_define_std (cpp_reader *pfile, const char *macro,
>> +            bool define_user)
>> +{
>> +  size_t len = strlen (macro);
>> +  char *buff = (char *) alloca (len + 5);
>> +  char *p = buff + 2;
>> +  char *q = p + len;
>> +
>> +  memcpy (p, macro, len + 1);
>> +  if (!(*p == '_' && (p[1] == '_' || ISUPPER (p[1]))))
>> +    {
>> +      if (*p != '_')
>> +    *--p = '_';
>> +      if (p[1] != '_')
>> +    *--p = '_';
>> +    }
>> +  cpp_define (pfile, p);
>> +
>> +  if (p != buff + 2)
>> +    {
>> +      if (q[-1] != '_')
>> +    *q++ = '_';
>> +      if (q[-2] != '_')
>> +    *q++ = '_';
>> +      *q = '\0';
>> +      cpp_define (pfile, p);
>> +      if (define_user)
>> +    cpp_define (pfile, macro);
>> +    }
>> +}
>> +
>> +/* Define MACRO to EXPANSION; if IS_STR, quote the expansion.  */
>> +
>> +static void
>> +gfc_builtin_define_with_value (cpp_reader *pfile, const char *macro,
>> +                   const char *expansion, int is_str)
>> +{
>> +  size_t mlen = strlen (macro);
>> +  size_t elen = strlen (expansion);
>> +  char *buf = (char *) alloca (mlen + elen + 4);
>> +  if (is_str)
>> +    sprintf (buf, "%s=\"%s\"", macro, expansion);
>> +  else
>> +    sprintf (buf, "%s=%s", macro, expansion);
>> +  cpp_define (pfile, buf);
>> +}
>> +
>> +/* Provide x86 CPU identification macros for the Fortran preprocessor.
>> +   TARGET_CPU_CPP_BUILTINS() cannot be called directly because it 
>> expands
>> +   to ix86_target_macros() in i386-c.cc, which is only linked into
>> +   C-family frontends.  This covers architecture identification and
>> +   float-size macros.  ISA feature macros (__SSE__, __AVX__, etc.) and
>> +   arch/tune macros (__znver4__, __skylake__, etc.) from
>> +   ix86_target_macros_internal() are not included; if needed, they could
>> +   be factored out of i386-c.cc into a shared object.  */
>> +
>> +#ifdef TARGET_80387
>> +static void
>> +gfc_define_ix86_target_macros (cpp_reader *pfile)
>> +{
>> +  if (TARGET_64BIT)
>> +    {
>> +      cpp_assert (pfile, "cpu=x86_64");
>> +      cpp_assert (pfile, "machine=x86_64");
>> +      cpp_define (pfile, "__amd64");
>> +      cpp_define (pfile, "__amd64__");
>> +      cpp_define (pfile, "__x86_64");
>> +      cpp_define (pfile, "__x86_64__");
>> +      if (TARGET_X32)
>> +    {
>> +      cpp_define (pfile, "_ILP32");
>> +      cpp_define (pfile, "__ILP32__");
>> +    }
>> +    }
>> +  else
>> +    {
>> +      cpp_assert (pfile, "cpu=i386");
>> +      cpp_assert (pfile, "machine=i386");
>> +      gfc_builtin_define_std (pfile, "i386", false);
>> +      cpp_define (pfile, "_ILP32");
>> +      cpp_define (pfile, "__ILP32__");
>> +    }
>> +
>> +  if (!TARGET_80387)
>> +    cpp_define (pfile, "_SOFT_FLOAT");
>> +
>> +  if (TARGET_LONG_DOUBLE_64)
>> +    cpp_define (pfile, "__LONG_DOUBLE_64__");
>> +
>> +  if (TARGET_LONG_DOUBLE_128)
>> +    cpp_define (pfile, "__LONG_DOUBLE_128__");
>> +
>> +  cpp_define_formatted (pfile, "__SIZEOF_FLOAT80__=%d",
>> +            GET_MODE_SIZE (XFmode));
>> +  cpp_define (pfile, "__SIZEOF_FLOAT128__=16");
>> +}
>> +#endif
>> +
>> +/* Provide essential Darwin platform macros for the Fortran 
>> preprocessor.
>> +   The full darwin_cpp_builtins() in darwin-c.cc also defines
>> +   __ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__ and
>> +   __CONSTANT_CFSTRINGS__, but those depend on functions only linked
>> +   into C-family frontends.  */
>> +
>> +static void ATTRIBUTE_UNUSED
>> +gfc_darwin_cpp_builtins (cpp_reader *pfile)
>> +{
>> +  cpp_define (pfile, "__MACH__");
>> +  cpp_define (pfile, "__APPLE__");
>> +  gfc_builtin_define_with_value (pfile, "__APPLE_CC__", "1", false);
>> +}
>>   static void
>>   cpp_define_builtins (cpp_reader *pfile)
>> @@ -177,33 +297,55 @@ cpp_define_builtins (cpp_reader *pfile)
>>     if (flag_openmp)
>>       cpp_define (pfile, "_OPENMP=202111");
>> -  /* The defines below are necessary for the TARGET_* macros.
>> -
>> -     FIXME:  Note that builtin_define_std() actually is a function
>> -     in c-cppbuiltin.cc which uses flags undefined for Fortran.
>> -     Let's skip this for now. If needed, one needs to look into it
>> -     once more.  */
>> +  /* Wrapper macros for C-family identifiers used in target config
>> +     headers.  These allow TARGET_OS_CPP_BUILTINS and
>> +     TARGET_OBJFMT_CPP_BUILTINS to compile in the Fortran frontend.  */
>>   # define builtin_define(TXT) cpp_define (pfile, TXT)
>> -# define builtin_define_std(TXT)
>> +# define builtin_define_std(TXT) gfc_builtin_define_std (pfile, 
>> TXT, !flag_iso)
>> +# define builtin_define_with_value(MACRO, EXPANSION, IS_STR) \
>> +  gfc_builtin_define_with_value (pfile, MACRO, EXPANSION, IS_STR)
>> +# define builtin_define_with_int_value(MACRO, VALUE) \
>> +  cpp_define_formatted (pfile, "%s=" HOST_WIDE_INT_PRINT_DEC, \
>> +            MACRO, (HOST_WIDE_INT) (VALUE))
>>   # define builtin_assert(TXT) cpp_assert (pfile, TXT)
>> +# define c_dialect_cxx() 0
>> +# define c_dialect_objc() 0
>> +# define preprocessing_asm_p() 0
>> +# define preprocessing_trad_p() 0
>> +  /* Fortran has no -std=cNN flag to control this.  Set to 1 (ISO mode)
>> +     so that builtin_define_std() only defines reserved-namespace macros
>> +     like __unix__ and __linux__, not bare "unix" or "linux" which are
>> +     valid Fortran identifiers and would cause silent replacement.  */
>> +# define flag_iso 1
>> +# define flag_isoc94 0
>> +# define flag_isoc99 0
>> +# define flag_isoc11 0
>> +# define flag_isoc23 0
>> +# define darwin_cpp_builtins(PFILE) gfc_darwin_cpp_builtins (PFILE)
>> -  /* FIXME: Pandora's Box
>> -    Using the macros below results in multiple breakages:
>> -     - mingw will fail to compile this file as dependent macros
>> -       assume to be used in c-cppbuiltin.cc only. Further, they use
>> -       flags only valid/defined in C (same as noted above).
>> -       [config/i386/mingw32.h, config/i386/cygming.h]
>> -     - other platforms (not as popular) break similarly
>> -       [grep for 'builtin_define_with_int_value' in gcc/config/]
>> -
>> -  TARGET_CPU_CPP_BUILTINS ();
>>     TARGET_OS_CPP_BUILTINS ();
>> -  TARGET_OBJFMT_CPP_BUILTINS (); */
>> +  TARGET_OBJFMT_CPP_BUILTINS ();
>> +
>> +#ifdef TARGET_80387
>> +  gfc_define_ix86_target_macros (pfile);
>> +#endif
>>   #undef builtin_define
>>   #undef builtin_define_std
>> +#undef builtin_define_with_value
>> +#undef builtin_define_with_int_value
>>   #undef builtin_assert
>> +#undef c_dialect_cxx
>> +#undef c_dialect_objc
>> +#undef preprocessing_asm_p
>> +#undef preprocessing_trad_p
>> +#undef flag_iso
>> +#undef flag_isoc94
>> +#undef flag_isoc99
>> +#undef flag_isoc11
>> +#undef flag_isoc23
>> +#undef darwin_cpp_builtins
>>   }
>>   bool
>> diff --git a/gcc/testsuite/gfortran.dg/gomp/declare-variant-10.f90 b/ 
>> gcc/testsuite/gfortran.dg/gomp/declare-variant-10.f90
>> index 0e0ab518010..115195e1194 100644
>> --- a/gcc/testsuite/gfortran.dg/gomp/declare-variant-10.f90
>> +++ b/gcc/testsuite/gfortran.dg/gomp/declare-variant-10.f90
>> @@ -64,9 +64,6 @@ contains
>>       call f18 ()      ! { dg-final { scan-tree-dump-times "f18 \\\(\\ 
>> \);" 1 "gimple" } } */
>>     end subroutine
>> -#if defined(__i386__) || defined(__x86_64__)
>> -  __attribute__((target ("avx512f,avx512bw")))
>> -#endif
>>     subroutine test2 ()
>>       !$omp target
>>         call f04 () ! { dg-final { scan-tree-dump-times "f03 \\\(\\ 
>> \);" 1 "gimple" { target { { i?86-*-* x86_64-*-* } && { ! ilp32 } } } } }
>> diff --git a/gcc/testsuite/gfortran.dg/pr42954-linux.f90 b/gcc/ 
>> testsuite/gfortran.dg/pr42954-linux.f90
>> new file mode 100644
>> index 00000000000..bd5efe7a237
>> --- /dev/null
>> +++ b/gcc/testsuite/gfortran.dg/pr42954-linux.f90
>> @@ -0,0 +1,24 @@
>> +! { dg-do preprocess { target *-*-linux* } }
>> +! { dg-options "-cpp" }
>> +!
>> +! PR fortran/42954 - target macros missing in gfortran -cpp
>> +
>> +#ifndef __linux__
>> +# error __linux__ not defined
>> +#endif
>> +
>> +#ifndef __linux
>> +# error __linux not defined
>> +#endif
>> +
>> +#ifndef __unix__
>> +# error __unix__ not defined
>> +#endif
>> +
>> +#ifndef __unix
>> +# error __unix not defined
>> +#endif
>> +
>> +#ifndef __ELF__
>> +# error __ELF__ not defined
>> +#endif
>> diff --git a/gcc/testsuite/gfortran.dg/pr42954-x86.f90 b/gcc/ 
>> testsuite/gfortran.dg/pr42954-x86.f90
>> new file mode 100644
>> index 00000000000..0a3b7eac8a2
>> --- /dev/null
>> +++ b/gcc/testsuite/gfortran.dg/pr42954-x86.f90
>> @@ -0,0 +1,10 @@
>> +! { dg-do preprocess { target { i?86-*-* x86_64-*-* } } }
>> +! { dg-options "-cpp" }
>> +!
>> +! PR fortran/42954 - target macros missing in gfortran -cpp
>> +
>> +#if !defined(__i386__) && !defined(__i386) \
>> +    && !defined(__x86_64__) && !defined(__x86_64) \
>> +    && !defined(__amd64__) && !defined(__amd64)
>> +# error x86 target macros not defined
>> +#endif
> 
> 
>