Projet_SETI_RISC-V/riscv-gnu-toolchain/gdb/gas/doc/c-rx.texi

@c Copyright (C) 2008-2022 Free Software Foundation, Inc.
@c This is part of the GAS manual.
@c For copying conditions, see the file as.texinfo.
@ifset GENERIC
@page
@node RX-Dependent
@chapter RX Dependent Features
@end ifset
@ifclear GENERIC
@node Machine Dependencies
@chapter RX Dependent Features
@end ifclear

@cindex RX support
@menu
* RX-Opts::                   RX Assembler Command-line Options
* RX-Modifiers::              Symbolic Operand Modifiers
* RX-Directives::             Assembler Directives
* RX-Float::                  Floating Point
* RX-Syntax::                 Syntax
@end menu

@node RX-Opts
@section RX Options
@cindex options, RX
@cindex RX options

The Renesas RX port of @code{@value{AS}} has a few target specific
command-line options:

@table @code

@cindex @samp{-m32bit-doubles}
@item -m32bit-doubles
This option controls the ABI and indicates to use a 32-bit float ABI.
It has no effect on the assembled instructions, but it does influence
the behaviour of the @samp{.double} pseudo-op.
This is the default.

@cindex @samp{-m64bit-doubles}
@item -m64bit-doubles
This option controls the ABI and indicates to use a 64-bit float ABI.
It has no effect on the assembled instructions, but it does influence
the behaviour of the @samp{.double} pseudo-op.

@cindex @samp{-mbig-endian}
@item -mbig-endian
This option controls the ABI and indicates to use a big-endian data
ABI.  It has no effect on the assembled instructions, but it does
influence the behaviour of the @samp{.short}, @samp{.hword}, @samp{.int},
@samp{.word}, @samp{.long}, @samp{.quad} and @samp{.octa} pseudo-ops.

@cindex @samp{-mlittle-endian}
@item -mlittle-endian
This option controls the ABI and indicates to use a little-endian data
ABI.  It has no effect on the assembled instructions, but it does
influence the behaviour of the @samp{.short}, @samp{.hword}, @samp{.int},
@samp{.word}, @samp{.long}, @samp{.quad} and @samp{.octa} pseudo-ops.
This is the default.

@cindex @samp{-muse-conventional-section-names}
@item -muse-conventional-section-names
This option controls the default names given to the code (.text),
initialised data (.data) and uninitialised data sections (.bss).

@cindex @samp{-muse-renesas-section-names}
@item -muse-renesas-section-names
This option controls the default names given to the code (P),
initialised data (D_1) and uninitialised data sections (B_1).
This is the default.

@cindex @samp{-msmall-data-limit}
@item -msmall-data-limit
This option tells the assembler that the small data limit feature of
the RX port of GCC is being used.  This results in the assembler
generating an undefined reference to a symbol called @code{__gp} for
use by the relocations that are needed to support the small data limit
feature.   This option is not enabled by default as it would otherwise
pollute the symbol table.

@cindex @samp{-mpid}
@item -mpid
This option tells the assembler that the position independent data of the
RX port of GCC is being used.  This results in the assembler
generating an undefined reference to a symbol called @code{__pid_base},
and also setting the RX_PID flag bit in the e_flags field of the ELF
header of the object file.

@cindex @samp{-mint-register}
@item -mint-register=@var{num}
This option tells the assembler how many registers have been reserved
for use by interrupt handlers.  This is needed in order to compute the
correct values for the @code{%gpreg} and @code{%pidreg} meta registers.

@cindex @samp{-mgcc-abi}
@item -mgcc-abi
This option tells the assembler that the old GCC ABI is being used by
the assembled code.  With this version of the ABI function arguments
that are passed on the stack are aligned to a 32-bit boundary.

@cindex @samp{-mrx-abi}
@item -mrx-abi
This option tells the assembler that the official RX ABI is being used
by the assembled code.  With this version of the ABI function
arguments that are passed on the stack are aligned to their natural
alignments.  This option is the default.

@cindex @samp{-mcpu=}
@item -mcpu=@var{name}
This option tells the assembler the target CPU type.  Currently the
@code{rx100}, @code{rx200}, @code{rx600}, @code{rx610}, @code{rxv2},
@code{rxv3} and @code{rxv3-dfpu} are recognised as valid cpu names.
Attempting to assemble an instructionnot supported by the indicated
cpu type will result in an error message being generated.

@cindex @samp{-mno-allow-string-insns}
@item -mno-allow-string-insns
This option tells the assembler to mark the object file that it is
building as one that does not use the string instructions
@code{SMOVF}, @code{SCMPU}, @code{SMOVB}, @code{SMOVU}, @code{SUNTIL}
@code{SWHILE} or the @code{RMPA} instruction.  In addition the mark
tells the linker to complain if an attempt is made to link the binary
with another one that does use any of these instructions.

Note - the inverse of this option, @code{-mallow-string-insns}, is
not needed.  The assembler automatically detects the use of the
the instructions in the source code and labels the resulting
object file appropriately.  If no string instructions are detected
then the object file is labelled as being one that can be linked with
either string-using or string-banned object files.
@end table

@node RX-Modifiers
@section Symbolic Operand Modifiers

@cindex RX modifiers
@cindex syntax, RX
@cindex %gp

The assembler supports one modifier when using symbol addresses
in RX instruction operands.  The general syntax is the following:

@smallexample
%gp(symbol)
@end smallexample

The modifier returns the offset from the @var{__gp} symbol to the
specified symbol as a 16-bit value.  The intent is that this offset
should be used in a register+offset move instruction when generating
references to small data.  Ie, like this:

@smallexample
  mov.W	 %gp(_foo)[%gpreg], r1
@end smallexample

The assembler also supports two meta register names which can be used
to refer to registers whose values may not be known to the
programmer.  These meta register names are:

@table @code

@cindex @samp{%gpreg}
@item %gpreg
The small data address register.

@cindex @samp{%pidreg}
@item %pidreg
The PID base address register.

@end table

Both registers normally have the value r13, but this can change if
some registers have been reserved for use by interrupt handlers or if
both the small data limit and position independent data features are
being used at the same time.

@node RX-Directives
@section Assembler Directives

@cindex assembler directives, RX
@cindex RX assembler directives

The RX version of @code{@value{AS}} has the following specific
assembler directives:

@table @code

@item .3byte
@cindex assembler directive .3byte, RX
@cindex RX assembler directive .3byte
Inserts a 3-byte value into the output file at the current location.

@item .fetchalign
@cindex assembler directive .fetchalign, RX
@cindex RX assembler directive .fetchalign
If the next opcode following this directive spans a fetch line
boundary (8 byte boundary), the opcode is aligned to that boundary.
If the next opcode does not span a fetch line, this directive has no
effect.  Note that one or more labels may be between this directive
and the opcode; those labels are aligned as well.  Any inserted bytes
due to alignment will form a NOP opcode.

@end table

@node RX-Float
@section Floating Point

@cindex floating point, RX
@cindex RX floating point

The floating point formats generated by directives are these.

@table @code
@cindex @code{float} directive, RX

@item .float
@code{Single} precision (32-bit) floating point constants.

@cindex @code{double} directive, RX
@item .double
If the @option{-m64bit-doubles} command-line option has been specified
then then @code{double} directive generates @code{double} precision
(64-bit) floating point constants, otherwise it generates
@code{single} precision (32-bit) floating point constants.  To force
the generation of 64-bit floating point constants used the @code{dc.d}
directive instead.

@end table

@node RX-Syntax
@section Syntax for the RX
@menu
* RX-Chars::                Special Characters
@end menu

@node RX-Chars
@subsection Special Characters

@cindex line comment character, RX
@cindex RX line comment character
The presence of a @samp{;} appearing anywhere on a line indicates the
start of a comment that extends to the end of that line.

If a @samp{#} appears as the first character of a line then the whole
line is treated as a comment, but in this case the line can also be a
logical line number directive (@pxref{Comments}) or a preprocessor
control command (@pxref{Preprocessing}).

@cindex line separator, RX
@cindex statement separator, RX
@cindex RX line separator
The @samp{!} character can be used to separate statements on the same
line.