fortran: use_iso_fortran_env_module tweaks [PR118337]

This patch adds a comment to explain why we initialize the non-constant
elts of symbol array separately and checking assert to verify that separate
initialization bumps the iterator for each macro.

2025-01-10  Jakub Jelinek  <jakub@redhat.com>

	PR fortran/118337
	* module.cc (use_iso_fortran_env_module): Add a comment explaining
	the optimization performed.  Add gcc_checking_assert that i was
	incremented for all the elements.  Formatting fix.

diff --git a/gcc/fortran/module.cc b/gcc/fortran/module.cc
index 63d0cdbee9f7cab25949485e311c3b54b9d9ff57..490eaa97a49db8bdd44425477cac60418cb2588e 100644 (file)
--- a/gcc/fortran/module.cc
+++ b/gcc/fortran/module.cc
@@ -7122,6 +7122,13 @@ use_iso_fortran_env_module (void)
 #include "iso-fortran-env.def"
     { ISOFORTRANENV_INVALID, NULL, -1234, 0 } };
 
+  /* We could have used c in the NAMED_{,U}INTCST macros
+     instead of 0, but then current g++ expands the initialization
+     as clearing the whole object followed by explicit stores of
+     all the non-zero elements (over 150), while by using 0s for
+     the non-constant initializers and initializing them afterwards
+     g++ will often copy everything from .rodata and then only override
+     over 30 non-constant ones.  */
   i = 0;
 #define NAMED_INTCST(a,b,c,d) symbol[i++].value = c;
 #define NAMED_UINTCST(a,b,c,d) symbol[i++].value = c;
@@ -7130,6 +7137,7 @@ use_iso_fortran_env_module (void)
 #define NAMED_FUNCTION(a,b,c,d) i++;
 #define NAMED_SUBROUTINE(a,b,c,d) i++;
 #include "iso-fortran-env.def"
+  gcc_checking_assert (i == (int) ARRAY_SIZE (symbol) - 1);
 
   /* Generate the symbol for the module itself.  */
   mod_symtree = gfc_find_symtree (gfc_current_ns->sym_root, mod);
@@ -7288,12 +7296,11 @@ use_iso_fortran_env_module (void)
            break;
 
 #define NAMED_FUNCTION(a,b,c,d) \
-               case a:
+         case a:
 #include "iso-fortran-env.def"
-                 create_intrinsic_function (symbol[i].name, symbol[i].id, mod,
-                                            INTMOD_ISO_FORTRAN_ENV, false,
-                                            NULL);
-                 break;
+           create_intrinsic_function (symbol[i].name, symbol[i].id, mod,
+                                      INTMOD_ISO_FORTRAN_ENV, false, NULL);
+           break;
 
          default:
            gcc_unreachable ();