diff options
Diffstat (limited to 'gcc/doc/tm.texi')
| -rw-r--r-- | gcc/doc/tm.texi | 133 |
1 files changed, 64 insertions, 69 deletions
diff --git a/gcc/doc/tm.texi b/gcc/doc/tm.texi index 35bd5c3c2b0..53f405b7862 100644 --- a/gcc/doc/tm.texi +++ b/gcc/doc/tm.texi @@ -4688,10 +4688,8 @@ to generate it on the spot. @end defmac @defmac TRAMPOLINE_SECTION -The name of a subroutine to switch to the section in which the -trampoline template is to be placed (@pxref{Sections}). The default is -a value of @samp{readonly_data_section}, which places the trampoline in -the section containing read-only data. +Return the section into which the trampoline template is to be placed +(@pxref{Sections}). The default value is @code{readonly_data_section}. @end defmac @defmac TRAMPOLINE_SIZE @@ -5914,9 +5912,32 @@ section}, which holds initialized writable data; and the @dfn{bss section}, which holds uninitialized data. Some systems have other kinds of sections. -The compiler must tell the assembler when to switch sections. These -macros control what commands to output to tell the assembler this. You -can also define additional sections. +@file{varasm.c} provides several well-known sections, such as +@code{text_section}, @code{data_section} and @code{bss_section}. +The normal way of controlling a @code{@var{foo}_section} variable +is to define the associated @code{@var{FOO}_SECTION_ASM_OP} macro, +as described below. The macros are only read once, when @file{varasm.c} +initializes itself, so their values must be run-time constants. +They may however depend on command-line flags. + +@emph{Note:} Some run-time files, such @file{crtstuff.c}, also make +use of the @code{@var{FOO}_SECTION_ASM_OP} macros, and expect them +to be string literals. + +Some assemblers require a different string to be written every time a +section is selected. If your assembler falls into this category, you +should define the @code{TARGET_ASM_INIT_SECTIONS} hook and use +@code{get_unnamed_section} to set up the sections. + +You must always create a @code{text_section}, either by defining +@code{TEXT_SECTION_ASM_OP} or by initializing @code{text_section} +in @code{TARGET_ASM_INIT_SECTIONS}. The same is true of +@code{data_section} and @code{DATA_SECTION_ASM_OP}. If you do not +create a distinct @code{readonly_data_section}, the default is to +reuse @code{text_section}. + +All the other @file{varasm.c} sections are optional, and are null +if the target does not provide them. @defmac TEXT_SECTION_ASM_OP A C expression whose value is a string, including spacing, containing the @@ -5941,22 +5962,18 @@ assembler operation to identify the following data as writable initialized data. Normally @code{"\t.data"} is right. @end defmac +@defmac SDATA_SECTION_ASM_OP +If defined, a C expression whose value is a string, including spacing, +containing the assembler operation to identify the following data as +initialized, writable small data. +@end defmac + @defmac READONLY_DATA_SECTION_ASM_OP A C expression whose value is a string, including spacing, containing the assembler operation to identify the following data as read-only initialized data. @end defmac -@defmac READONLY_DATA_SECTION -A macro naming a function to call to switch to the proper section for -read-only data. The default is to use @code{READONLY_DATA_SECTION_ASM_OP} -if defined, else fall back to @code{text_section}. - -The most common definition will be @code{data_section}, if the target -does not have a special read-only data section, and does not put data -in the text section. -@end defmac - @defmac BSS_SECTION_ASM_OP If defined, a C expression whose value is a string, including spacing, containing the assembler operation to identify the following data as @@ -5967,6 +5984,12 @@ uninitialized global data will be output in the data section if used. @end defmac +@defmac SBSS_SECTION_ASM_OP +If defined, a C expression whose value is a string, including spacing, +containing the assembler operation to identify the following data as +uninitialized, writable small data. +@end defmac + @defmac INIT_SECTION_ASM_OP If defined, a C expression whose value is a string, including spacing, containing the assembler operation to identify the following data as @@ -6016,23 +6039,6 @@ arbitrary boundary. This is used to force all fragments of the and thus prevent the linker from having to add any padding. @end defmac -@findex in_text -@findex in_data -@defmac EXTRA_SECTIONS -A list of names for sections other than the standard two, which are -@code{in_text} and @code{in_data}. You need not define this macro -on a system with no other sections (that GCC needs to use). -@end defmac - -@findex text_section -@findex data_section -@defmac EXTRA_SECTION_FUNCTIONS -One or more functions to be defined in @file{varasm.c}. These -functions should do jobs analogous to those of @code{text_section} and -@code{data_section}, for your additional sections. Do not define this -macro if you do not define @code{EXTRA_SECTIONS}. -@end defmac - @defmac JUMP_TABLES_IN_TEXT_SECTION Define this macro to be an expression with a nonzero value if jump tables (for @code{tablejump} insns) should be output in the text @@ -6042,15 +6048,23 @@ readonly data section is used. This macro is irrelevant if there is no separate readonly data section. @end defmac -@deftypefn {Target Hook} void TARGET_ASM_SELECT_SECTION (tree @var{exp}, int @var{reloc}, unsigned HOST_WIDE_INT @var{align}) -Switches to the appropriate section for output of @var{exp}. You can +@deftypefn {Target Hook} void TARGET_ASM_INIT_SECTIONS (void) +Define this hook if you need to do something special to set up the +@file{varasm.c} sections, or if your target has some special sections +of its own that you need to create. + +GCC calls this hook after processing the command line, but before writing +any assembly code, and before calling any of the section-returning hooks +described below. +@end deftypefn + +@deftypefn {Target Hook} {section *} TARGET_ASM_SELECT_SECTION (tree @var{exp}, int @var{reloc}, unsigned HOST_WIDE_INT @var{align}) +Return the section into which @var{exp} should be placed. You can assume that @var{exp} is either a @code{VAR_DECL} node or a constant of some sort. @var{reloc} indicates whether the initial value of @var{exp} requires link-time relocations. Bit 0 is set when variable contains local relocations only, while bit 1 is set for global relocations. -Select the section by calling @code{data_section} or one of the -alternatives for other sections. @var{align} is the constant alignment -in bits. +@var{align} is the constant alignment in bits. The default version of this function takes care of putting read-only variables in @code{readonly_data_section}. @@ -6079,22 +6093,21 @@ example, the function @code{foo} would be placed in @code{.text.foo}. Whatever the actual target object format, this is often good enough. @end deftypefn -@deftypefn {Target Hook} void TARGET_ASM_FUNCTION_RODATA_SECTION (tree @var{decl}) -Switches to a readonly data section associated with +@deftypefn {Target Hook} {section *} TARGET_ASM_FUNCTION_RODATA_SECTION (tree @var{decl}) +Return the readonly data section associated with @samp{DECL_SECTION_NAME (@var{decl})}. -The default version of this function switches to @code{.gnu.linkonce.r.name} -section if function's section is @code{.gnu.linkonce.t.name}, to -@code{.rodata.name} if function is in @code{.text.name} section -and otherwise switches to the normal readonly data section. +The default version of this function selects @code{.gnu.linkonce.r.name} if +the function's section is @code{.gnu.linkonce.t.name}, @code{.rodata.name} +if function is in @code{.text.name}, and the normal readonly-data section +otherwise. @end deftypefn -@deftypefn {Target Hook} void TARGET_ASM_SELECT_RTX_SECTION (enum machine_mode @var{mode}, rtx @var{x}, unsigned HOST_WIDE_INT @var{align}) -Switches to the appropriate section for output of constant pool entry -@var{x} in @var{mode}. You can assume that @var{x} is some kind of +@deftypefn {Target Hook} {section *} TARGET_ASM_SELECT_RTX_SECTION (enum machine_mode @var{mode}, rtx @var{x}, unsigned HOST_WIDE_INT @var{align}) +Return the section into which a constant @var{x}, of mode @var{mode}, +should be placed. You can assume that @var{x} is some kind of constant in RTL@. The argument @var{mode} is redundant except in the -case of a @code{const_int} rtx. Select the section by calling -@code{readonly_data_section} or one of the alternatives for other -sections. @var{align} is the constant alignment in bits. +case of a @code{const_int} rtx. @var{align} is the constant alignment +in bits. The default version of this function takes care of putting symbolic constants in @code{flag_pic} mode in @code{data_section} and everything @@ -7742,24 +7755,6 @@ minimum alignment otherwise. @xref{SDB and DWARF}. Only applicable if the target supports DWARF 2 frame unwind information. @end defmac -@deftypefn {Target Hook} void TARGET_ASM_EXCEPTION_SECTION () -If defined, a function that switches to the section in which the main -exception table is to be placed (@pxref{Sections}). The default is a -function that switches to a section named @code{.gcc_except_table} on -machines that support named sections via -@code{TARGET_ASM_NAMED_SECTION}, otherwise if @option{-fpic} or -@option{-fPIC} is in effect, the @code{data_section}, otherwise the -@code{readonly_data_section}. -@end deftypefn - -@deftypefn {Target Hook} void TARGET_ASM_EH_FRAME_SECTION () -If defined, a function that switches to the section in which the DWARF 2 -frame unwind information to be placed (@pxref{Sections}). The default -is a function that outputs a standard GAS section directive, if -@code{EH_FRAME_SECTION_NAME} is defined, or else a data section -directive followed by a synthetic label. -@end deftypefn - @deftypevar {Target Hook} bool TARGET_TERMINATE_DW2_EH_FRAME_INFO Contains the value true if the target should add a zero word onto the end of a Dwarf-2 frame info section when used for exception handling. |