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__attribute__
Target-specific attributes may be defined for functions, data and types. These are described using the following target hooks; they also need to be documented in extend.texi.
If defined, this target hook points to an array of `struct attribute_spec' (defined in tree-core.h) specifying the machine specific attributes for this target and some of the restrictions on the entities to which these attributes are applied and the arguments they take.
If defined, this target hook is a function which returns true if the machine-specific attribute named name expects an identifier given as its first argument to be passed on as a plain identifier, not subjected to name lookup. If this is not defined, the default is false for all machine-specific attributes.
If defined, this target hook is a function which returns zero if the attributes on type1 and type2 are incompatible, one if they are compatible, and two if they are nearly compatible (which causes a warning to be generated). If this is not defined, machine-specific attributes are supposed always to be compatible.
If defined, this target hook is a function which assigns default attributes to the newly defined type.
Define this target hook if the merging of type attributes needs special handling. If defined, the result is a list of the combined
TYPE_ATTRIBUTES
of type1 and type2. It is assumed thatcomptypes
has already been called and returned 1. This function may callmerge_attributes
to handle machine-independent merging.
Define this target hook if the merging of decl attributes needs special handling. If defined, the result is a list of the combined
DECL_ATTRIBUTES
of olddecl and newdecl. newdecl is a duplicate declaration of olddecl. Examples of when this is needed are when one attribute overrides another, or when an attribute is nullified by a subsequent definition. This function may callmerge_attributes
to handle machine-independent merging.If the only target-specific handling you require is `dllimport' for Microsoft Windows targets, you should define the macro
TARGET_DLLIMPORT_DECL_ATTRIBUTES
to1
. The compiler will then define a function calledmerge_dllimport_decl_attributes
which can then be defined as the expansion ofTARGET_MERGE_DECL_ATTRIBUTES
. You can also addhandle_dll_attribute
in the attribute table for your port to perform initial processing of the `dllimport' and `dllexport' attributes. This is done in i386/cygwin.h and i386/i386.cc, for example.
decl is a variable or function with
__attribute__((dllimport))
specified. Use this hook if the target needs to add extra validation checks tohandle_dll_attribute
.
Define this macro to a nonzero value if you want to treat
__declspec(X)
as equivalent to__attribute((X))
. By default, this behavior is enabled only for targets that defineTARGET_DLLIMPORT_DECL_ATTRIBUTES
. The current implementation of__declspec
is via a built-in macro, but you should not rely on this implementation detail.
Define this target hook if you want to be able to add attributes to a decl when it is being created. This is normally useful for back ends which wish to implement a pragma by using the attributes which correspond to the pragma's effect. The node argument is the decl which is being created. The attr_ptr argument is a pointer to the attribute list for this decl. The list itself should not be modified, since it may be shared with other decls, but attributes may be chained on the head of the list and
*
attr_ptr modified to point to the new attributes, or a copy of the list may be made if further changes are needed.
Define this target hook if you want to be able to perform additional target-specific processing of an attribute which is handled generically by a front end. The arguments are the same as those which are passed to attribute handlers. So far this only affects the noinit and section attribute.
This target hook returns
true
if it is OK to inline fndecl into the current function, despite its having target-specific attributes,false
otherwise. By default, if a function has a target specific attribute attached to it, it will not be inlined.
This hook is called to parse
attribute(target("..."))
, which allows setting target-specific options on individual functions. These function-specific options may differ from the options specified on the command line. The hook should returntrue
if the options are valid.The hook should set the
DECL_FUNCTION_SPECIFIC_TARGET
field in the function declaration to hold a pointer to a target-specificstruct cl_target_option
structure.
This hook is called to save any additional target-specific information in the
struct cl_target_option
structure for function-specific options from thestruct gcc_options
structure. See Option file format.
This hook is called to restore any additional target-specific information in the
struct cl_target_option
structure for function-specific options to thestruct gcc_options
structure.
This hook is called to update target-specific information in the
struct cl_target_option
structure after it is streamed in from LTO bytecode.
This hook is called to print any additional target-specific information in the
struct cl_target_option
structure for function-specific options.
This target hook parses the options for
#pragma GCC target
, which sets the target-specific options for functions that occur later in the input stream. The options accepted should be the same as those handled by theTARGET_OPTION_VALID_ATTRIBUTE_P
hook.
Sometimes certain combinations of command options do not make sense on a particular target machine. You can override the hook
TARGET_OPTION_OVERRIDE
to take account of this. This hooks is called once just after all the command options have been parsed.Don't use this hook to turn on various extra optimizations for -O. That is what
TARGET_OPTION_OPTIMIZATION
is for.If you need to do something whenever the optimization level is changed via the optimize attribute or pragma, see
TARGET_OVERRIDE_OPTIONS_AFTER_CHANGE
This target hook returns
true
if DECL1 and DECL2 are versions of the same function. DECL1 and DECL2 are function versions if and only if they have the same function signature and different target specific attributes, that is, they are compiled for different target machines.
This target hook returns
false
if the caller function cannot inline callee, based on target specific information. By default, inlining is not allowed if the callee function has function specific target options and the caller does not use the same options.
Allow target to analyze all gimple statements for the given function to record and update some target specific information for inlining. A typical example is that a caller with one isa feature disabled is normally not allowed to inline a callee with that same isa feature enabled even which is attributed by always_inline, but with the conservative analysis on all statements of the callee if we are able to guarantee the callee does not exploit any instructions from the mismatch isa feature, it would be safe to allow the caller to inline the callee. info is one
unsigned int
value to record information in which one set bit indicates one corresponding feature is detected in the analysis, stmt is the statement being analyzed. Return true if target still need to analyze the subsequent statements, otherwise return false to stop subsequent analysis. The default version of this hook returns false.
Allow target to check early whether it is necessary to analyze all gimple statements in the given function to update target specific information for inlining. See hook
update_ipa_fn_target_info
for usage example of target specific information. This hook is expected to be invoked ahead of the iterating with hookupdate_ipa_fn_target_info
. decl is the function being analyzed, info is the same as what in hookupdate_ipa_fn_target_info
, target can do one time update into info without iterating for some case. Return true if target decides to analyze all gimple statements to collect information, otherwise return false. The default version of this hook returns false.