Darwin, Arm64 : Proof-of-principle hack Fortran to use descriptors for nested.

This adds a descriptor-based implementation and then
addresses Issue gcc-mirror#32 by adjusting the nested function hack to use
bit 1 rather than bit 2.

NOTE: that Arm reserve both bits 0 and 1 for furture use, so that this
is no less a hack than using bit 2 - but it might be a somewhat more
compatible hack.

Tested with the example in Issue gcc-mirror#32 (otherwise, there's no real change
in the testsuite).

Author: iains

gcc/c/c-lang.c

@@ -38,6 +38,9 @@ enum c_language_kind c_language = clk_c;
 #undef LANG_HOOKS_INIT_TS
 #define LANG_HOOKS_INIT_TS c_common_init_ts
 
+#undef LANG_HOOKS_CUSTOM_FUNCTION_DESCRIPTORS
+#define LANG_HOOKS_CUSTOM_FUNCTION_DESCRIPTORS true
+
 #if CHECKING_P
 #undef LANG_HOOKS_RUN_LANG_SELFTESTS
 #define LANG_HOOKS_RUN_LANG_SELFTESTS selftest::run_c_tests

gcc/config/aarch64/aarch64.c

@@ -26573,9 +26573,9 @@ aarch64_libgcc_floating_mode_supported_p
 #define TARGET_DWARF_POLY_INDETERMINATE_VALUE \
   aarch64_dwarf_poly_indeterminate_value
 
-/* The architecture reserves bits 0 and 1 so use bit 2 for descriptors.  */
+/* The architecture reserves bits 0 and 1 but hack 1 for now.  */
 #undef TARGET_CUSTOM_FUNCTION_DESCRIPTORS
-#define TARGET_CUSTOM_FUNCTION_DESCRIPTORS 4
+#define TARGET_CUSTOM_FUNCTION_DESCRIPTORS 2
 
 #undef TARGET_HARD_REGNO_NREGS
 #define TARGET_HARD_REGNO_NREGS aarch64_hard_regno_nregs

gcc/config/i386/darwin.h

@@ -308,3 +308,8 @@ along with GCC; see the file COPYING3.  If not see
 #define CLEAR_INSN_CACHE(beg, end)				\
   extern void sys_icache_invalidate(void *start, size_t len);	\
   sys_icache_invalidate ((beg), (size_t)((end)-(beg)))
+
+/* Make sure that any code we generate is compatible with the Fortran/Ada
+   function descriptor impl.  */
+#undef FUNCTION_BOUNDARY
+#define FUNCTION_BOUNDARY 16

gcc/fortran/f95-lang.c

@@ -175,6 +175,8 @@ static const struct attribute_spec gfc_attribute_table[] =
 #define LANG_HOOKS_BUILTIN_FUNCTION	gfc_builtin_function
 #define LANG_HOOKS_GET_ARRAY_DESCR_INFO	gfc_get_array_descr_info
 #define LANG_HOOKS_ATTRIBUTE_TABLE	gfc_attribute_table
+#undef LANG_HOOKS_CUSTOM_FUNCTION_DESCRIPTORS
+#define LANG_HOOKS_CUSTOM_FUNCTION_DESCRIPTORS true
 
 struct lang_hooks lang_hooks = LANG_HOOKS_INITIALIZER;
 

gcc/fortran/trans-expr.c

@@ -7637,6 +7637,8 @@ gfc_conv_procedure_call (gfc_se * se, gfc_symbol * sym,
   arglist = retargs;
 
   /* Generate the actual call.  */
+  bool is_proc_ptr_comp = gfc_is_proc_ptr_comp (expr);
+
   if (base_object == NULL_TREE)
     conv_function_val (se, sym, expr, args);
   else
@@ -7662,6 +7664,11 @@ gfc_conv_procedure_call (gfc_se * se, gfc_symbol * sym,
 
   fntype = TREE_TYPE (TREE_TYPE (se->expr));
   se->expr = build_call_vec (TREE_TYPE (fntype), se->expr, arglist);
+  tree ff = CALL_EXPR_FN (se->expr);
+  if (ff && INDIRECT_REF_P (ff))
+    ff = TREE_OPERAND (ff, 0);
+  if (is_proc_ptr_comp || !ff || VAR_P (ff) || TREE_CODE (ff) == PARM_DECL)
+    CALL_EXPR_BY_DESCRIPTOR (se->expr) = true;
 
   /* Allocatable scalar function results must be freed and nullified
      after use. This necessitates the creation of a temporary to

gcc/fortran/trans.c

@@ -332,6 +332,14 @@ gfc_build_addr_expr (tree type, tree t)
   else
     natural_type = build_pointer_type (base_type);
 
+  /* If this is a nested function that uses the static chain, or if
+     optimization is disabled (a static chain will be added automatically)
+     then call by descriptor.  */
+  bool fn_with_static_chain = false;
+  if (TREE_CODE (t) == FUNCTION_DECL
+      && (DECL_STATIC_CHAIN (t) || (!optimize && decl_function_context (t))))
+    fn_with_static_chain = true;
+
   if (TREE_CODE (t) == INDIRECT_REF)
     {
       if (!type)
@@ -350,6 +358,9 @@ gfc_build_addr_expr (tree type, tree t)
   if (type && natural_type != type)
     t = convert (type, t);
 
+  if (fn_with_static_chain)
+    FUNC_ADDR_BY_DESCRIPTOR (t) = true;
+
   return t;
 }