internals.texi

基于4个mips核的noc设计

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.

@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.

@item NO_PSEUDO_DOT
@cindex NO_PSEUDO_DOT
If you define this macro, GAS will not require pseudo-ops to start with a
@kbd{.} character.

@item TC_EQUAL_IN_INSN
@cindex TC_EQUAL_IN_INSN
If you define this macro, it should return nonzero if the instruction is
permitted to contain an @kbd{=} character.  GAS will call it with two
arguments, the character before the @kbd{=} character, and the value of
@code{input_line_pointer} at that point.  GAS uses this macro to decide if a
@kbd{=} is an assignment or an instruction.

@item TC_EOL_IN_INSN
@cindex TC_EOL_IN_INSN
If you define this macro, it should return nonzero if the current input line
pointer should be treated as the end of a line.

@item md_parse_name
@cindex md_parse_name
If this macro is defined, GAS will call it for any symbol found in an
expression.  You can define this to handle special symbols in a special way.
If a symbol always has a certain value, you should normally enter it in the
symbol table, perhaps using @code{reg_section}.

@item md_undefined_symbol
@cindex md_undefined_symbol
GAS will call this function when a symbol table lookup fails, before it
creates a new symbol.  Typically this would be used to supply symbols whose
name or value changes dynamically, possibly in a context sensitive way.
Predefined symbols with fixed values, such as register names or condition
codes, are typically entered directly into the symbol table when @code{md_begin}
is called.  One argument is passed, a @code{char *} for the symbol.

@item md_operand
@cindex md_operand
GAS will call this function with one argument, an @code{expressionS}
pointer, for any expression that can not be recognized.  When the function
is called, @code{input_line_pointer} will point to the start of the
expression.

@item tc_unrecognized_line
@cindex tc_unrecognized_line
If you define this macro, GAS will call it when it finds a line that it can not
parse.

@item md_do_align
@cindex md_do_align
You may define this macro to handle an alignment directive.  GAS will call it
when the directive is seen in the input file.  For example, the i386 backend
uses this to generate efficient nop instructions of varying lengths, depending
upon the number of bytes that the alignment will skip.

@item HANDLE_ALIGN
@cindex HANDLE_ALIGN
You may define this macro to do special handling for an alignment directive.
GAS will call it at the end of the assembly.

@item TC_IMPLICIT_LCOMM_ALIGNMENT (@var{size}, @var{p2var})
@cindex TC_IMPLICIT_LCOMM_ALIGNMENT
An @code{.lcomm} directive with no explicit alignment parameter will use this
macro to set @var{p2var} to the alignment that a request for @var{size} bytes
will have.  The alignment is expressed as a power of two.  If no alignment
should take place, the macro definition should do nothing.  Some targets define
a @code{.bss} directive that is also affected by this macro.  The default
definition will set @var{p2var} to the truncated power of two of sizes up to
eight bytes.

@item md_flush_pending_output
@cindex md_flush_pending_output
If you define this macro, GAS will call it each time it skips any space because of a
space filling or alignment or data allocation pseudo-op.

@item TC_PARSE_CONS_EXPRESSION
@cindex TC_PARSE_CONS_EXPRESSION
You may define this macro to parse an expression used in a data allocation
pseudo-op such as @code{.word}.  You can use this to recognize relocation
directives that may appear in such directives.

@item BITFIELD_CONS_EXPRESSION
@cindex BITFIELD_CONS_EXPRESSION
If you define this macro, GAS will recognize bitfield instructions in data
allocation pseudo-ops, as used on the i960.

@item REPEAT_CONS_EXPRESSION
@cindex REPEAT_CONS_EXPRESSION
If you define this macro, GAS will recognize repeat counts in data allocation
pseudo-ops, as used on the MIPS.

@item md_cons_align
@cindex md_cons_align
You may define this macro to do any special alignment before a data allocation
pseudo-op.

@item TC_CONS_FIX_NEW
@cindex TC_CONS_FIX_NEW
You may define this macro to generate a fixup for a data allocation pseudo-op.

@item TC_INIT_FIX_DATA (@var{fixp})
@cindex TC_INIT_FIX_DATA
A C statement to initialize the target specific fields of fixup @var{fixp}.
These fields are defined with the @code{TC_FIX_TYPE} macro.

@item TC_FIX_DATA_PRINT (@var{stream}, @var{fixp})
@cindex TC_FIX_DATA_PRINT
A C statement to output target specific debugging information for
fixup @var{fixp} to @var{stream}.  This macro is called by @code{print_fixup}.

@item TC_FRAG_INIT (@var{fragp})
@cindex TC_FRAG_INIT
A C statement to initialize the target specific fields of frag @var{fragp}.
These fields are defined with the @code{TC_FRAG_TYPE} macro.

@item md_number_to_chars
@cindex md_number_to_chars
This should just call either @code{number_to_chars_bigendian} or
@code{number_to_chars_littleendian}, whichever is appropriate.  On targets like
the MIPS which support options to change the endianness, which function to call
is a runtime decision.  On other targets, @code{md_number_to_chars} can be a
simple macro.

@item md_reloc_size
@cindex md_reloc_size
This variable is only used in the original version of gas (not
@code{BFD_ASSEMBLER} and not @code{MANY_SEGMENTS}).  It holds the size of a
relocation entry.

@item WORKING_DOT_WORD
@itemx md_short_jump_size
@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
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
This function returns an estimate of the size of a @code{rs_machine_dependent}
frag before any relaxing is done.  It may also create any necessary
relocations.

@item md_relax_frag
@cindex md_relax_frag
This macro may be defined to relax a frag.  GAS will call this with the
segment, the frag, and the change in size of all previous frags;
@code{md_relax_frag} should return the change in size of the frag.
@xref{Relaxation}.

@item TC_GENERIC_RELAX_TABLE
@cindex TC_GENERIC_RELAX_TABLE
If you do not define @code{md_relax_frag}, you may define
@code{TC_GENERIC_RELAX_TABLE} as a table of @code{relax_typeS} structures.  The
machine independent code knows how to use such a table to relax PC relative
references.  See @file{tc-m68k.c} for an example.  @xref{Relaxation}.

@item md_prepare_relax_scan
@cindex md_prepare_relax_scan
If defined, it is a C statement that is invoked prior to scanning
the relax table.

@item LINKER_RELAXING_SHRINKS_ONLY
@cindex LINKER_RELAXING_SHRINKS_ONLY
If you define this macro, and the global variable @samp{linkrelax} is set
(because of a command line option, or unconditionally in @code{md_begin}), a
@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.
The instruction is completed using the data from the relaxation pass.
It may also create any necessary relocations.
@xref{Relaxation}.

@item md_apply_fix
@cindex md_apply_fix
GAS will call this for each fixup.  It should store the correct value in the
object file.  @code{fixup_segment} performs a generic overflow check on the
@code{valueT *val} argument after @code{md_apply_fix} returns.  If the overflow
check is relevant for the target machine, then @code{md_apply_fix} should
modify @code{valueT *val}, typically to the value stored in the object file.

@item TC_HANDLES_FX_DONE
@cindex TC_HANDLES_FX_DONE
If this macro is defined, it means that @code{md_apply_fix} correctly sets the
@code{fx_done} field in the fixup.

@item tc_gen_reloc
@cindex tc_gen_reloc
A @code{BFD_ASSEMBLER} GAS will call this to generate a reloc.  GAS will pass
the resulting reloc to @code{bfd_install_relocation}.  This currently works
poorly, as @code{bfd_install_relocation} often does the wrong thing, and
instances of @code{tc_gen_reloc} have been written to work around the problems,
which in turns makes it difficult to fix @code{bfd_install_relocation}.

@item RELOC_EXPANSION_POSSIBLE
@cindex RELOC_EXPANSION_POSSIBLE
If you define this macro, it means that @code{tc_gen_reloc} may return multiple
relocation entries for a single fixup.  In this case, the return value of
@code{tc_gen_reloc} is a pointer to a null terminated array.

@item MAX_RELOC_EXPANSION
@cindex MAX_RELOC_EXPANSION
You must define this if @code{RELOC_EXPANSION_POSSIBLE} is defined; it
indicates the largest number of relocs which @code{tc_gen_reloc} may return for
a single fixup.

@item tc_fix_adjustable
@cindex tc_fix_adjustable
You may define this macro to indicate whether a fixup against a locally defined
symbol should be adjusted to be against the section symbol.  It should return a
non-zero value if the adjustment is acceptable.

@item MD_PCREL_FROM_SECTION
@cindex MD_PCREL_FROM_SECTION
If you define this macro, it should return the offset between the address of a
PC relative fixup and the position from which the PC relative adjustment should
be made.  On many processors, the base of a PC relative instruction is the next
instruction, so this macro would return the length of an instruction.

@item md_pcrel_from
@cindex md_pcrel_from
This is the default value of @code{MD_PCREL_FROM_SECTION}.  The difference is
that @code{md_pcrel_from} does not take a section argument.

@item tc_frob_label
@cindex tc_frob_label
If you define this macro, GAS will call it each time a label is defined.

@item md_section_align
@cindex md_section_align
GAS will call this function for each section at the end of the assembly, to
permit the CPU backend to adjust the alignment of a section.  The function
must take two arguments, a @code{segT} for the section and a @code{valueT}
for the size of the section, and return a @code{valueT} for the rounded
size.

@item md_macro_start
@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.

@item md_macro_info
@cindex md_macro_info
If defined, GAS will call this macro after the macro expansion has been
included in the input and after parsing the macro arguments.  The single
argument is a pointer to the macro processing's internal representation of the
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.

@item DOUBLEBAR_PARALLEL
@cindex DOUBLEBAR_PARALLEL
Affects the preprocessor so that lines containing '||' don't have their
whitespace stripped following the double bar.  This is useful for targets that
implement parallel instructions.

@item KEEP_WHITE_AROUND_COLON
@cindex KEEP_WHITE_AROUND_COLON
Normally, whitespace is compressed and removed when, in the presence of the
colon, the adjoining tokens can be distinguished.  This option affects the
preprocessor so that whitespace around colons is preserved.  This is useful
when colons might be removed from the input after preprocessing but before
assembling, so that adjoining tokens can still be distinguished if there is
whitespace, or concatentated if there is not.

@item tc_frob_section
@cindex tc_frob_section
If you define this macro, a @code{BFD_ASSEMBLER} GAS will call it for each
section at the end of the assembly.

@item tc_frob_file_before_adjust
@cindex tc_frob_file_before_adjust
If you define this macro, GAS will call it after the symbol values are
resolved, but before the fixups have been changed from local symbols to section
symbols.

@item tc_frob_symbol
@cindex tc_frob_symbol
If you define this macro, GAS will call it for each symbol.  You can indicate
that the symbol should not be included in the object file by definining this
macro to set its second argument to a non-zero value.

@item tc_frob_file
@cindex tc_frob_file
If you define this macro, GAS will call it after the symbol table has been
completed, but before the relocations have been generated.

@item tc_frob_file_after_relocs
If you define this macro, GAS will call it after the relocs have been
generated.