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Diffstat (limited to 'contrib/binutils/gas/doc/internals.texi')
| -rw-r--r-- | contrib/binutils/gas/doc/internals.texi | 62 |
1 files changed, 50 insertions, 12 deletions
diff --git a/contrib/binutils/gas/doc/internals.texi b/contrib/binutils/gas/doc/internals.texi index 8453c48..a42bc0f 100644 --- a/contrib/binutils/gas/doc/internals.texi +++ b/contrib/binutils/gas/doc/internals.texi @@ -8,8 +8,7 @@ This chapter describes the internals of the assembler. It is incomplete, but it may help a bit. -This chapter was last modified on $Date: 2000/03/26 14:47:33 $. It is not updated regularly, and it -may be out of date. +This chapter is not updated regularly, and it may be out of date. @menu * GAS versions:: GAS versions @@ -464,7 +463,7 @@ the other fields; see the definition in @file{expr.h} for the possibilities. An @code{operatorT} value of @code{O_big} indicates either a floating point number, stored in the global variable @code{generic_floating_point_number}, or -an integer to large to store in an @code{offsetT} type, stored in the global +an integer too large to store in an @code{offsetT} type, stored in the global array @code{generic_bignum}. This rather inflexible approach makes it impossible to use floating point numbers or large expressions in complex expressions. @@ -645,7 +644,7 @@ The variable characters are to be repeated @code{fr_offset} times. If have this type. @item rs_leb128 -This state is used to implement the DWARF ``little endian base 128'' +This state is used to implement the DWARF ``little endian base 128'' variable length number format. The @code{fr_symbol} is always an expression symbol, as constant expressions are emitted directly. The @code{fr_offset} field is used during relaxation to hold the previous size of the number so @@ -774,6 +773,12 @@ variable. Normally the default value of @samp{generic} is fine. The configuration process will create a file named @file{targ-env.h} in the build directory which includes @file{te-@var{em}.h}. +There is a special case for COFF. For historical reason, the GNU COFF +assembler doesn't follow the documented behavior on certain debug symbols for +the compatibility with other COFF assemblers. A port can define +@code{STRICTCOFF} in the configure script to make the GNU COFF assembler +to follow the documented behavior. + Porting GAS to a new CPU requires writing the @file{tc-@var{CPU}} files. Porting GAS to a new object file format requires writing the @file{obj-@var{fmt}} files. There is sometimes some interaction between these @@ -884,7 +889,7 @@ pseudo-ops which are specific to the CPU. If this macro is defined, GAS will call it with a @code{pseudo_typeS} argument. It should return non-zero if the pseudo-op is a conditional which controls whether code is assembled, such as @samp{.if}. GAS knows about the normal -conditional pseudo-ops,and you should normally not have to define this macro. +conditional pseudo-ops, and you should normally not have to define this macro. @item comment_chars @cindex comment_chars @@ -913,7 +918,7 @@ comment when they appear at the start of a line. @item line_separator_chars @cindex line_separator_chars This is a null terminated @code{const char} array of characters which separate -lines (semicolon and newline are such characters by default, and need not be +lines (null and newline are such characters by default, and need not be listed in this array). Note that line_separator_chars do not separate lines if found in a comment, such as after a character in line_comment_chars or comment_chars. @@ -965,7 +970,7 @@ default value is @code{LEX_NAME | LEX_BEGIN_NAME}. @item NUMBERS_WITH_SUFFIX @cindex NUMBERS_WITH_SUFFIX When this macro is defined to be non-zero, the parser allows the radix of a -constant to be indicated with a suffix. Valid suffixes are binary (B), +constant to be indicated with a suffix. Valid suffixes are binary (B), octal (Q), and hexadecimal (H). Case is not significant. @item SINGLE_QUOTE_STRINGS @@ -992,6 +997,7 @@ If you define this macro, GAS will assume that any text at the start of a line is a label, even if it does not have a colon. @item TC_START_LABEL +@itemx TC_START_LABEL_WITHOUT_COLON @cindex TC_START_LABEL You may define this macro to control what GAS considers to be a label. The default definition is to accept any name followed by a colon character. @@ -999,7 +1005,7 @@ default definition is to accept any name followed by a colon character. @item TC_START_LABEL_WITHOUT_COLON @cindex TC_START_LABEL_WITHOUT_COLON Same as TC_START_LABEL, but should be used instead of TC_START_LABEL when -LABELS_WITHOUT_COLONS is defined. +LABELS_WITHOUT_COLONS is defined. @item NO_PSEUDO_DOT @cindex NO_PSEUDO_DOT @@ -1133,11 +1139,13 @@ relocation entry. @itemx md_long_jump_size @itemx md_create_short_jump @itemx md_create_long_jump +@itemx TC_CHECK_ADJUSTED_BROKEN_DOT_WORD @cindex WORKING_DOT_WORD @cindex md_short_jump_size @cindex md_long_jump_size @cindex md_create_short_jump @cindex md_create_long_jump +@cindex TC_CHECK_ADJUSTED_BROKEN_DOT_WORD If @code{WORKING_DOT_WORD} is defined, GAS will not do broken word processing (@pxref{Broken words}). Otherwise, you should set @code{md_short_jump_size} to the size of a short jump (a jump that is just long enough to jump around a @@ -1145,6 +1153,10 @@ number of long jumps) and @code{md_long_jump_size} to the size of a long jump (a jump that can go anywhere in the function). You should define @code{md_create_short_jump} to create a short jump around a number of long jumps, and define @code{md_create_long_jump} to create a long jump. +If defined, the macro TC_CHECK_ADJUSTED_BROKEN_DOT_WORD will be called for each +adjusted word just before the word is output. The macro takes two arguments, +an @code{addressT} with the adjusted word and a pointer to the current +@code{struct broken_word}. @item md_estimate_size_before_relax @cindex md_estimate_size_before_relax @@ -1177,6 +1189,15 @@ If you define this macro, and the global variable @samp{linkrelax} is set @samp{.align} directive will cause extra space to be allocated. The linker can then discard this space when relaxing the section. +@item TC_LINKRELAX_FIXUP (@var{segT}) +@cindex TC_LINKRELAX_FIXUP +If defined, this macro allows control over whether fixups for a +given section will be processed when the @var{linkrelax} variable is +set. The macro is given the N_TYPE bits for the section in its +@var{segT} argument. If the macro evaluates to a non-zero value +then the fixups will be converted into relocs, otherwise they will +be passed to @var{md_apply_fix3} as normal. + @item md_convert_frag @cindex md_convert_frag GAS will call this for each rs_machine_dependent fragment. @@ -1251,7 +1272,7 @@ size. @cindex md_macro_start If defined, GAS will call this macro when it starts to include a macro expansion. @code{macro_nest} indicates the current macro nesting level, which -includes the one being expanded. +includes the one being expanded. @item md_macro_info @cindex md_macro_info @@ -1263,7 +1284,7 @@ macro (macro_entry *), which includes expansion of the formal arguments. @item md_macro_end @cindex md_macro_end Complement to md_macro_start. If defined, it is called when finished -processing an inserted macro expansion, just before decrementing macro_nest. +processing an inserted macro expansion, just before decrementing macro_nest. @item DOUBLEBAR_PARALLEL @cindex DOUBLEBAR_PARALLEL @@ -1332,6 +1353,13 @@ source line. The default value is 4. @item LISTING_RHS_WIDTH The maximum number of characters to print from one line of the input file. The default value is 100. + +@item TC_COFF_SECTION_DEFAULT_ATTRIBUTES +@cindex TC_COFF_SECTION_DEFAULT_ATTRIBUTES +The COFF @code{.section} directive will use the value of this macro to set +a new section's attributes when a directive has no valid flags or when the +flag is @code{w}. The default value of the macro is @code{SEC_LOAD | SEC_DATA}. + @end table @node Object format backend @@ -1400,8 +1428,8 @@ generate a @code{.file} symbol if none was generated previously. @item SEPARATE_STAB_SECTIONS @cindex SEPARATE_STAB_SECTIONS -You may define this macro to indicate that stabs should be placed in separate -sections, as in ELF. +You may define this macro to a nonzero value to indicate that stabs should be +placed in separate sections, as in ELF. @item INIT_STAB_SECTION @cindex INIT_STAB_SECTION @@ -1573,6 +1601,16 @@ called to convert the frag to an @code{rs_fill} frag with no variant part. Sometimes changing addressing modes may also require rewriting the instruction. It can be accessed via @code{fr_opcode} or @code{fr_fix}. +If you generate frags separately for the basic insn opcode and any relaxable +operands, do not call @code{fix_new} thinking you can emit fixups for the +opcode field from the relaxable frag. It is not garanteed to be the same frag. +If you need to emit fixups for the opcode field from inspection of the +relaxable frag, then you need to generate a common frag for both the basic +opcode and relaxable fields, or you need to provide the frag for the opcode to +pass to @code{fix_new}. The latter can be done for example by defining +@code{TC_FRAG_TYPE} to include a pointer to it and defining @code{TC_FRAG_INIT} +to set the pointer. + Sometimes @code{fr_var} is increased instead, and @code{frag_wane} is not called. I'm not sure, but I think this is to keep @code{fr_fix} referring to an earlier byte, and @code{fr_subtype} set to @code{rs_machine_dependent} so |
