[flang] Support target-specialized C int types

[peixin]

Summary

Currently, C_INTMAX_T is 64-bit integer in stdint.h on 64-bit linux
machine. Make it c_int128_t until it is supported.

On non-win32 and non-mach machine, C_INT_FAST16_T and C_INT_FAST32_T are
defined as long int. The detailed info can be obtained as follows:

! test.c
#include <stdint.h>

$ clang test.c -E
...
typedef signed char int_fast8_t;

typedef long int int_fast16_t;
typedef long int int_fast32_t;
typedef long int int_fast64_t;
...

Fixes #58282.

[peixin]

flang/module/iso_c_binding.f90

49

I find this rule by looking at intel definition /opt/intel/oneapi/compiler/2022.0.2/linux/compiler/include/iso_c_binding.f90:

! On linux the following C types (int8_t .. intmax_t) are defined in stdint.h
! Support for C types on Windows.
!DEC$ IF DEFINED(_WIN32)
    INTEGER (KIND=4), PARAMETER :: C_INT8_T = 1
    INTEGER (KIND=4), PARAMETER :: C_INT16_T = 2
    INTEGER (KIND=4), PARAMETER :: C_INT32_T = 4
    INTEGER (KIND=4), PARAMETER :: C_INT64_T = 8
    INTEGER (KIND=4), PARAMETER :: C_INT_LEAST8_T = 1
    INTEGER (KIND=4), PARAMETER :: C_INT_LEAST16_T = 2
    INTEGER (KIND=4), PARAMETER :: C_INT_LEAST32_T = 4
    INTEGER (KIND=4), PARAMETER :: C_INT_LEAST64_T = 8
    INTEGER (KIND=4), PARAMETER :: C_INT_FAST8_T = 1
    INTEGER (KIND=4), PARAMETER :: C_INT_FAST16_T = 2
    INTEGER (KIND=4), PARAMETER :: C_INT_FAST32_T = 4
    INTEGER (KIND=4), PARAMETER :: C_INT_FAST64_T = 8
    INTEGER (KIND=4), PARAMETER :: C_INTMAX_T = 8
!DEC$ ELSEIF DEFINED(__MACH__)
    INTEGER (KIND=4), PARAMETER :: C_INT8_T = 1
    INTEGER (KIND=4), PARAMETER :: C_INT16_T = 2
    INTEGER (KIND=4), PARAMETER :: C_INT32_T = 4
    INTEGER (KIND=4), PARAMETER :: C_INT64_T = 8
    INTEGER (KIND=4), PARAMETER :: C_INT_LEAST8_T = 1
    INTEGER (KIND=4), PARAMETER :: C_INT_LEAST16_T = 2
    INTEGER (KIND=4), PARAMETER :: C_INT_LEAST32_T = 4
    INTEGER (KIND=4), PARAMETER :: C_INT_LEAST64_T = 8
    INTEGER (KIND=4), PARAMETER :: C_INT_FAST8_T = 1
    INTEGER (KIND=4), PARAMETER :: C_INT_FAST16_T = 2
    INTEGER (KIND=4), PARAMETER :: C_INT_FAST32_T = 4
    INTEGER (KIND=4), PARAMETER :: C_INT_FAST64_T = 8
    INTEGER (KIND=4), PARAMETER :: C_INTMAX_T = 8
!DEC$ ELSE
    INTEGER (KIND=4), PARAMETER :: C_INT8_T = 1
    INTEGER (KIND=4), PARAMETER :: C_INT16_T = 2
    INTEGER (KIND=4), PARAMETER :: C_INT32_T = 4
    INTEGER (KIND=4), PARAMETER :: C_INT64_T = 8
    INTEGER (KIND=4), PARAMETER :: C_INT_LEAST8_T = 1
    INTEGER (KIND=4), PARAMETER :: C_INT_LEAST16_T = 2
    INTEGER (KIND=4), PARAMETER :: C_INT_LEAST32_T = 4
    INTEGER (KIND=4), PARAMETER :: C_INT_LEAST64_T = 8
    INTEGER (KIND=4), PARAMETER :: C_INT_FAST8_T = 1
    INTEGER (KIND=4), PARAMETER :: C_INT_FAST16_T = POINTER_LEN
    INTEGER (KIND=4), PARAMETER :: C_INT_FAST32_T = POINTER_LEN
    INTEGER (KIND=4), PARAMETER :: C_INT_FAST64_T = 8
    INTEGER (KIND=4), PARAMETER :: C_INTMAX_T = 8
!DEC$ ENDIF

I also double checked one minwg32 and mach machine.

[sscalpone]

@peixin It seems these code snippets from Intel are part of a copyrighted file, owned by Intel. Do you know if LLVM has a policy about including such code, even in a code review like this?

[peixin]

In D135666#3853783, @sscalpone wrote:

@peixin It seems these code snippets from Intel are part of a copyrighted file, owned by Intel. Do you know if LLVM has a policy about including such code, even in a code review like this?

Sorry. How should I do for now? It seems that I don't have the permission to remove it or Phabricator does not support it?

[peixin]

@sscalpone Should I abandon this PR or ask help from the administrator to remove it?

flang/module/iso_c_binding.f90

use __Fortran_builtins, only: &
     c_funptr => __builtin_c_funptr, &
     c_sizeof => sizeof, &
     c_loc => __builtin_c_loc
 
   type(c_ptr), parameter :: c_null_ptr = c_ptr(0)
   type(c_funptr), parameter :: c_null_funptr = c_funptr(0)
 
   ! Table 18.2 (in clause 18.3.1)
-  ! TODO: Specialize (via macros?) for alternative targets
+  ! The following C types (c_int8_t .. c_intmax_t) are defined in stdint.h on
+  ! linux (/usr/include/stdint.h).
   integer, parameter :: &
     c_int8_t = 1, &
     c_int16_t = 2, &
     c_int32_t = 4, &
     c_int64_t = 8, &
     c_int128_t = 16 ! anticipating future addition
   integer, parameter :: &
     c_int = c_int32_t, &
     c_short = c_int16_t, &
     c_long = c_int64_t, &
     c_long_long = c_int64_t, &
     c_signed_char = c_int8_t, &
     c_size_t = kind(c_sizeof(1)), &
-    c_intmax_t = c_int128_t, &
+    c_intmax_t = c_int64_t, & ! Is c_int128_t if it is supported in future
     c_intptr_t = c_size_t, &
     c_ptrdiff_t = c_size_t
   integer, parameter :: &
     c_int_least8_t = c_int8_t, &
-    c_int_fast8_t = c_int8_t, &
     c_int_least16_t = c_int16_t, &
-    c_int_fast16_t = c_int16_t, &
     c_int_least32_t = c_int32_t, &
-    c_int_fast32_t = c_int32_t, &
     c_int_least64_t = c_int64_t, &
-    c_int_fast64_t = c_int64_t, &
     c_int_least128_t = c_int128_t, &
     c_int_fast128_t = c_int128_t
+#if defined(_WIN32) || defined(__MACH__)
+  integer, parameter :: &
+    c_int_fast8_t = c_int8_t, &
+    c_int_fast16_t = c_int16_t, &
+    c_int_fast32_t = c_int32_t, &
+    c_int_fast64_t = c_int64_t
+#else
+  integer, parameter :: &
+    c_int_fast8_t = c_int8_t, &
+    c_int_fast16_t = c_int64_t, &
+    c_int_fast32_t = c_int64_t, &
+    c_int_fast64_t = c_int64_t
+#endif
 
   integer, parameter :: &
     c_float = 4, &
     c_double = 8, &
 #if __x86_64__
     c_long_double = 10
 #else
     c_long_double = 16