Ping
See also https://gcc.gnu.org/ml/gcc-patches/2019-10/msg00413.html
for more details about why this seemed like a good idea. A shorter
version of that message (well, it started out that way :-)) is that
it lets us use:
#ifndef _ARM_SVE_H_
#define _ARM_SVE_H_
#include <stdint.h>
typedef __fp16 float16_t;
typedef float float32_t;
typedef double float64_t;
#pragma GCC aarch64 "arm_sve.h"
#endif
as the full intrinsics header file. Rather than have GCC call:
add_builtin_function ("__builtin_aarch64_svarsd_s16_n_x",
fntype, code, BUILT_IN_MD, NULL, attrs);
at start-up and having the header file provide an inline wrapper like:
__extension__ extern __inline svint8_t
__attribute__ ((__always_inline__, __gnu_inline__, __artificial__))
svasrd_n_s16_x (svbool_t __a, svint8_t __b, int64_t __c)
{
return __builtin_aarch64_svasrd_n_s16_x (__a, __b, __c);
}
we can just have GCC call:
simulate_builtin_function_decl (input_location, "svasrd_n_s16_x",
fntype, code, NULL, attrs);
when the header pragma is invoked.
When repeated for thousands of functions, this significantly reduces
the amount of code needed. It also gives quicker start-up times
(because functions are only registered when they're needed) and makes
arm_sve.h compile more quickly (because there's less code to parse).
Another benefit is that inline wrappers don't show up in error messages.
E.g.:
#include <arm_neon.h>
int8x8_t foo (int16x8_t x, int y)
{ return vqrshrn_n_s16 (x, y); }
gives:
In file included from foo.c:3:10:
In function 'vqrshrn_n_s16',
inlined from 'foo' at foo.c:2:
include/arm_neon.h:24419:10: error: argument 2 must be a constant immediate
24419 | return (int8x8_t) __builtin_aarch64_sqrshrn_nv8hi (__a, __b);
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
where the quoted line is the inline wrapper in arm_neon.h rather than
the user's code. An SVE example like:
#include <arm_sve.h>
svint16_t foo (svbool_t pg, svint16_t x, int y)
{ return svasrd_x (pg, x, y); }
instead gives:
foo.c: In function 'foo':
foo.c:3:10: error: argument 3 of 'svasrd_x' must be an integer constant
expression
3 | { return svasrd_x (pg, x, y); }
| ^~~~~~~~
which seems more user-friendly.
Thanks,
Richard
Richard Sandiford <richard.sandif...@arm.com> writes:
> Although it's possible to define the SVE intrinsics in a normal header
> file, it's much more convenient to define them directly in the compiler.
> This also speeds up compilation and gives better error messages.
>
> The idea is therefore for arm_sve.h (the main intrinsics header file)
> to have the pragma:
>
> #pragma GCC aarch64 "arm_sve.h"
>
> telling GCC to define (almost) everything arm_sve.h needs to define.
> The target then needs a way of injecting new built-in function
> declarations during compilation.
>
> The main hook for defining built-in functions is add_builtin_function.
> This is designed for use at start-up, and so has various features that
> are correct in that context but not for the pragma above:
>
> (1) the location is always BUILTINS_LOCATION, whereas for arm_sve.h
> it ought to be the location of the pragma.
>
> (2) the function is only immediately visible if it's in the implementation
> namespace, whereas the pragma is deliberately injecting functions
> into the general namespace.
>
> (3) there's no attempt to emulate a normal function declaration in
> C or C++, whereas functions declared by the pragma should be
> checked in the same way as an open-coded declaration would be.
> E.g. we should get an error if there was a previous incompatible
> declaration.
>
> (4) in C++, the function is treated as extern "C" and so can't be
> overloaded, whereas SVE intrinsics do use function overloading.
>
> This patch therefore adds a hook that targets can use to inject
> the equivalent of a source-level function declaration, but bound
> to a BUILT_IN_MD function.
>
> The main SVE intrinsic patch has tests to make sure that we report an
> error for conflicting definitions that appear either before or after
> including arm_sve.h.
>
> Tested on aarch64-linux-gnu and x86_64-linux-gnu. OK to install?
>
> Richard
2019-09-26 Richard Sandiford <richard.sandif...@arm.com>
gcc/
* langhooks.h (lang_hooks::simulate_builtin_function_decl): New hook.
(simulate_builtin_function_decl): Declare.
* langhooks-def.h (LANG_HOOKS_SIMULATE_BUILTIN_FUNCTION_DECL): Define.
(LANG_HOOKS_INITIALIZER): Include it.
* langhooks.c (add_builtin_function_common): Rename to...
(build_builtin_function): ...this. Add a location parameter and use
it instead of BUILTINS_LOCATION. Remove the hook parameter and return
the decl instead.
(add_builtin_function): Update accordingly, passing the returned
decl to the lang hook.
(add_builtin_function_ext_scope): Likewise
(simulate_builtin_function_decl): New function.
gcc/c/
* c-tree.h (c_simulate_builtin_function_decl): Declare.
* c-decl.c (c_simulate_builtin_function_decl): New function.
* c-objc-common.h (LANG_HOOKS_SIMULATE_BUILTIN_FUNCTION_DECL): Define
to the above.
gcc/cp/
* cp-tree.h (cxx_simulate_builtin_function_decl): Declare.
* decl.c (builtin_function_1): Add an is_simulated_source_decl
parameter. When true, treat the function as a C++ function
rather than as extern "C", and don't treat it as anticipated.
(cxx_simulate_builtin_function_decl): New function.
* cp-objcp-common.h (LANG_HOOKS_SIMULATE_BUILTIN_FUNCTION_DECL): Define
to the above.
Index: gcc/langhooks.h
===================================================================
--- gcc/langhooks.h 2019-03-08 18:15:33.660751905 +0000
+++ gcc/langhooks.h 2019-09-26 13:02:42.543520465 +0100
@@ -494,6 +494,15 @@ struct lang_hooks
backend must add all of the builtins at program initialization time. */
tree (*builtin_function_ext_scope) (tree decl);
+ /* Do language-specific processing for target-specific built-in
+ function DECL, so that it is defined in the global scope (only)
+ and is available without needing to be explicitly declared.
+
+ This is intended for targets that want to inject declarations of
+ built-in functions into the source language (such as in response
+ to a pragma) rather than providing them in the source language itself. */
+ tree (*simulate_builtin_function_decl) (tree decl);
+
/* Used to set up the tree_contains_structure array for a frontend. */
void (*init_ts) (void);
@@ -562,6 +571,8 @@ extern tree add_builtin_function_ext_sco
enum built_in_class cl,
const char *library_name,
tree attrs);
+extern tree simulate_builtin_function_decl (location_t, const char *, tree,
+ int, const char *, tree);
extern tree add_builtin_type (const char *name, tree type);
/* Language helper functions. */
Index: gcc/langhooks-def.h
===================================================================
--- gcc/langhooks-def.h 2019-03-08 18:15:39.328730361 +0000
+++ gcc/langhooks-def.h 2019-09-26 13:02:42.543520465 +0100
@@ -122,6 +122,7 @@ #define LANG_HOOKS_TREE_SIZE lhd_tree_s
#define LANG_HOOKS_TYPES_COMPATIBLE_P lhd_types_compatible_p
#define LANG_HOOKS_BUILTIN_FUNCTION lhd_builtin_function
#define LANG_HOOKS_BUILTIN_FUNCTION_EXT_SCOPE LANG_HOOKS_BUILTIN_FUNCTION
+#define LANG_HOOKS_SIMULATE_BUILTIN_FUNCTION_DECL LANG_HOOKS_BUILTIN_FUNCTION
#define LANG_HOOKS_EXPR_TO_DECL lhd_expr_to_decl
#define LANG_HOOKS_TO_TARGET_CHARSET lhd_to_target_charset
#define LANG_HOOKS_INIT_TS lhd_do_nothing
@@ -338,6 +339,7 @@ #define LANG_HOOKS_INITIALIZER { \
LANG_HOOKS_GIMPLIFY_EXPR, \
LANG_HOOKS_BUILTIN_FUNCTION, \
LANG_HOOKS_BUILTIN_FUNCTION_EXT_SCOPE, \
+ LANG_HOOKS_SIMULATE_BUILTIN_FUNCTION_DECL, \
LANG_HOOKS_INIT_TS, \
LANG_HOOKS_EXPR_TO_DECL, \
LANG_HOOKS_EH_PERSONALITY, \
Index: gcc/langhooks.c
===================================================================
--- gcc/langhooks.c 2019-08-25 19:10:35.194159619 +0100
+++ gcc/langhooks.c 2019-09-26 13:02:42.543520465 +0100
@@ -599,19 +599,16 @@ lhd_omp_mappable_type (tree type)
return true;
}
-/* Common function for add_builtin_function and
- add_builtin_function_ext_scope. */
+/* Common function for add_builtin_function, add_builtin_function_ext_scope
+ and simulate_builtin_function_decl. */
+
static tree
-add_builtin_function_common (const char *name,
- tree type,
- int function_code,
- enum built_in_class cl,
- const char *library_name,
- tree attrs,
- tree (*hook) (tree))
+build_builtin_function (location_t location, const char *name, tree type,
+ int function_code, enum built_in_class cl,
+ const char *library_name, tree attrs)
{
tree id = get_identifier (name);
- tree decl = build_decl (BUILTINS_LOCATION, FUNCTION_DECL, id, type);
+ tree decl = build_decl (location, FUNCTION_DECL, id, type);
TREE_PUBLIC (decl) = 1;
DECL_EXTERNAL (decl) = 1;
@@ -632,8 +629,7 @@ add_builtin_function_common (const char
else
decl_attributes (&decl, NULL_TREE, 0);
- return hook (decl);
-
+ return decl;
}
/* Create a builtin function. */
@@ -646,9 +642,9 @@ add_builtin_function (const char *name,
const char *library_name,
tree attrs)
{
- return add_builtin_function_common (name, type, function_code, cl,
- library_name, attrs,
- lang_hooks.builtin_function);
+ tree decl = build_builtin_function (BUILTINS_LOCATION, name, type,
+ function_code, cl, library_name, attrs);
+ return lang_hooks.builtin_function (decl);
}
/* Like add_builtin_function, but make sure the scope is the external scope.
@@ -666,9 +662,40 @@ add_builtin_function_ext_scope (const ch
const char *library_name,
tree attrs)
{
- return add_builtin_function_common (name, type, function_code, cl,
- library_name, attrs,
- lang_hooks.builtin_function_ext_scope);
+ tree decl = build_builtin_function (BUILTINS_LOCATION, name, type,
+ function_code, cl, library_name, attrs);
+ return lang_hooks.builtin_function_ext_scope (decl);
+}
+
+/* Simulate a declaration of a target-specific built-in function at
+ location LOCATION, as though it had been declared directly in the
+ source language. NAME is the name of the function, TYPE is its function
+ type, FUNCTION_CODE is the target-specific function code, LIBRARY_NAME
+ is the name of the underlying library function (NULL if none) and
+ ATTRS is a list of function attributes.
+
+ Return the decl of the declared function. */
+
+tree
+simulate_builtin_function_decl (location_t location, const char *name,
+ tree type, int function_code,
+ const char *library_name, tree attrs)
+{
+ tree decl = build_builtin_function (location, name, type,
+ function_code, BUILT_IN_MD,
+ library_name, attrs);
+ tree new_decl = lang_hooks.simulate_builtin_function_decl (decl);
+
+ /* Give the front end a chance to create a new decl if necessary,
+ but if the front end discards the decl in favour of a conflicting
+ (erroneous) previous definition, return the decl that we tried but
+ failed to add. This allows the caller to process the returned decl
+ normally, even though the source code won't be able to use it. */
+ if (TREE_CODE (new_decl) == FUNCTION_DECL
+ && fndecl_built_in_p (new_decl, function_code, BUILT_IN_MD))
+ return new_decl;
+
+ return decl;
}
tree
Index: gcc/c/c-tree.h
===================================================================
--- gcc/c/c-tree.h 2019-07-10 19:41:20.543944894 +0100
+++ gcc/c/c-tree.h 2019-09-26 13:02:42.539520492 +0100
@@ -579,6 +579,7 @@ extern struct c_declarator *set_array_de
struct c_declarator *);
extern tree c_builtin_function (tree);
extern tree c_builtin_function_ext_scope (tree);
+extern tree c_simulate_builtin_function_decl (tree);
extern void shadow_tag (const struct c_declspecs *);
extern void shadow_tag_warned (const struct c_declspecs *, int);
extern tree start_enum (location_t, struct c_enum_contents *, tree);
Index: gcc/c/c-decl.c
===================================================================
--- gcc/c/c-decl.c 2019-09-21 13:56:06.983948786 +0100
+++ gcc/c/c-decl.c 2019-09-26 13:02:42.539520492 +0100
@@ -4481,6 +4481,16 @@ c_builtin_function_ext_scope (tree decl)
return decl;
}
+
+/* Implement LANG_HOOKS_SIMULATE_BUILTIN_FUNCTION_DECL. */
+
+tree
+c_simulate_builtin_function_decl (tree decl)
+{
+ tree type = TREE_TYPE (decl);
+ C_DECL_BUILTIN_PROTOTYPE (decl) = prototype_p (type);
+ return pushdecl (decl);
+}
/* Called when a declaration is seen that contains no names to declare.
If its type is a reference to a structure, union or enum inherited
Index: gcc/c/c-objc-common.h
===================================================================
--- gcc/c/c-objc-common.h 2019-04-04 08:34:51.661939350 +0100
+++ gcc/c/c-objc-common.h 2019-09-26 13:02:42.539520492 +0100
@@ -60,6 +60,9 @@ #define LANG_HOOKS_MISSING_NORETURN_OK_P
#define LANG_HOOKS_BUILTIN_FUNCTION c_builtin_function
#undef LANG_HOOKS_BUILTIN_FUNCTION_EXT_SCOPE
#define LANG_HOOKS_BUILTIN_FUNCTION_EXT_SCOPE c_builtin_function_ext_scope
+#undef LANG_HOOKS_SIMULATE_BUILTIN_FUNCTION_DECL
+#define LANG_HOOKS_SIMULATE_BUILTIN_FUNCTION_DECL \
+ c_simulate_builtin_function_decl
#undef LANG_HOOKS_EMITS_BEGIN_STMT
#define LANG_HOOKS_EMITS_BEGIN_STMT true
Index: gcc/cp/cp-tree.h
===================================================================
--- gcc/cp/cp-tree.h 2019-09-26 08:38:00.759713359 +0100
+++ gcc/cp/cp-tree.h 2019-09-26 13:02:42.539520492 +0100
@@ -6461,6 +6461,7 @@ extern tmpl_spec_kind current_tmpl_spec_
extern tree cp_fname_init (const char *, tree *);
extern tree cxx_builtin_function (tree decl);
extern tree cxx_builtin_function_ext_scope (tree decl);
+extern tree cxx_simulate_builtin_function_decl (tree);
extern tree check_elaborated_type_specifier (enum tag_types, tree, bool);
extern void warn_extern_redeclared_static (tree, tree);
extern tree cxx_comdat_group (tree);
Index: gcc/cp/decl.c
===================================================================
--- gcc/cp/decl.c 2019-09-17 15:27:10.958069743 +0100
+++ gcc/cp/decl.c 2019-09-26 13:02:42.543520465 +0100
@@ -71,7 +71,6 @@ static tree grokvardecl (tree, tree, tre
int, int, int, bool, int, tree, location_t);
static void check_static_variable_definition (tree, tree);
static void record_unknown_type (tree, const char *);
-static tree builtin_function_1 (tree, tree, bool);
static int member_function_or_else (tree, tree, enum overload_flags);
static tree local_variable_p_walkfn (tree *, int *, void *);
static const char *tag_name (enum tag_types);
@@ -4567,8 +4566,12 @@ cp_make_fname_decl (location_t loc, tree
return decl;
}
+/* IS_SIMULATED_DECL is true if the decl should simulate a global
+ declaration in the source language. */
+
static tree
-builtin_function_1 (tree decl, tree context, bool is_global)
+builtin_function_1 (tree decl, tree context, bool is_global,
+ bool is_simulated_decl = false)
{
tree id = DECL_NAME (decl);
const char *name = IDENTIFIER_POINTER (id);
@@ -4576,7 +4579,10 @@ builtin_function_1 (tree decl, tree cont
retrofit_lang_decl (decl);
DECL_ARTIFICIAL (decl) = 1;
- SET_DECL_LANGUAGE (decl, lang_c);
+ if (is_simulated_decl)
+ SET_DECL_LANGUAGE (decl, lang_cplusplus);
+ else
+ SET_DECL_LANGUAGE (decl, lang_c);
/* Runtime library routines are, by definition, available in an
external shared object. */
DECL_VISIBILITY (decl) = VISIBILITY_DEFAULT;
@@ -4584,21 +4590,24 @@ builtin_function_1 (tree decl, tree cont
DECL_CONTEXT (decl) = context;
- /* A function in the user's namespace should have an explicit
- declaration before it is used. Mark the built-in function as
- anticipated but not actually declared. */
- if (name[0] != '_' || name[1] != '_')
- DECL_ANTICIPATED (decl) = 1;
- else if (strncmp (name + 2, "builtin_", strlen ("builtin_")) != 0)
- {
- size_t len = strlen (name);
-
- /* Treat __*_chk fortification functions as anticipated as well,
- unless they are __builtin_*. */
- if (len > strlen ("___chk")
- && memcmp (name + len - strlen ("_chk"),
- "_chk", strlen ("_chk") + 1) == 0)
+ if (!is_simulated_decl)
+ {
+ /* A function in the user's namespace should have an explicit
+ declaration before it is used. Mark the built-in function as
+ anticipated but not actually declared. */
+ if (name[0] != '_' || name[1] != '_')
DECL_ANTICIPATED (decl) = 1;
+ else if (strncmp (name + 2, "builtin_", strlen ("builtin_")) != 0)
+ {
+ size_t len = strlen (name);
+
+ /* Treat __*_chk fortification functions as anticipated as well,
+ unless they are __builtin_*. */
+ if (len > strlen ("___chk")
+ && memcmp (name + len - strlen ("_chk"),
+ "_chk", strlen ("_chk") + 1) == 0)
+ DECL_ANTICIPATED (decl) = 1;
+ }
}
if (is_global)
@@ -4650,6 +4659,14 @@ cxx_builtin_function_ext_scope (tree dec
return builtin_function_1 (decl, NULL_TREE, true);
}
+/* Implement LANG_HOOKS_SIMULATE_BUILTIN_FUNCTION_DECL. */
+
+tree
+cxx_simulate_builtin_function_decl (tree decl)
+{
+ return builtin_function_1 (decl, NULL_TREE, true, true);
+}
+
/* Generate a FUNCTION_DECL with the typical flags for a runtime library
function. Not called directly. */
Index: gcc/cp/cp-objcp-common.h
===================================================================
--- gcc/cp/cp-objcp-common.h 2019-03-08 18:15:25.000784821 +0000
+++ gcc/cp/cp-objcp-common.h 2019-09-26 13:02:42.539520492 +0100
@@ -100,6 +100,9 @@ #define LANG_HOOKS_POST_COMPILATION_PARS
#define LANG_HOOKS_BUILTIN_FUNCTION cxx_builtin_function
#undef LANG_HOOKS_BUILTIN_FUNCTION_EXT_SCOPE
#define LANG_HOOKS_BUILTIN_FUNCTION_EXT_SCOPE cxx_builtin_function_ext_scope
+#undef LANG_HOOKS_SIMULATE_BUILTIN_FUNCTION_DECL
+#define LANG_HOOKS_SIMULATE_BUILTIN_FUNCTION_DECL \
+ cxx_simulate_builtin_function_decl
#undef LANG_HOOKS_TYPE_HASH_EQ
#define LANG_HOOKS_TYPE_HASH_EQ cxx_type_hash_eq
#undef LANG_HOOKS_COPY_LANG_QUALIFIERS
