Better organization, indexing, for MIPS-dep section.
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Roland Pesch
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f2cdeec493
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03d2167461
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@ -7112,48 +7112,110 @@ set addr(rd),imm4 subl rrd,addr(rs)
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@node Machine Dependencies
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@chapter MIPS Dependent Features
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@end ifclear
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The MIPS @value{AS} supports the MIPS R2000 and R3000 processors.
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It ignores the @samp{-nocpp} option.
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@cindex MIPS R2000
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@cindex MIPS R3000
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@sc{gnu} @code{@value{AS}} for @sc{mips} architectures supports the @sc{mips}
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@sc{r2000} and @sc{r3000} processors. For information about the @sc{mips}
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instruction set, see @cite{MIPS RISC Architecture}, by Kane and Heindrich
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(Prentice-Hall).
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Not all traditional MIPS macro instructions are currently supported.
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Specifically, @code{li.d} and @code{li.s} are not currently supported.
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@menu
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* MIPS Opts:: Assembler options
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* MIPS Object:: ECOFF object code
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* MIPS Stabs:: Directives for debugging information
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* MIPS Missing:: Missing instructions
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@end menu
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Assembling for a MIPS ECOFF target supports some additional sections
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@node MIPS Opts
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@section Assembler options
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The @sc{mips} configurations of @sc{gnu} @code{@value{AS}} support three
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special options, and accept one other for command-line compatibility.
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@table @code
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@cindex @code{-G} option (MIPS)
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@item -G @var{num}
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This option sets the largest size of an object that can be referenced
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implicitly with the @code{gp} register. It is only accepted for targets
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that use @sc{ecoff} format. The default value is 8.
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@cindex @code{-EB} option (MIPS)
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@cindex @code{-EL} option (MIPS)
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@cindex MIPS big-endian output
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@cindex MIPS little-endian output
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@cindex big-endian output, MIPS
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@cindex little-endian output, MIPS
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@item -EB
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@itemx -EL
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Any @sc{mips} configuration of @code{@value{AS}} can select big-endian or
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little-endian output at run time (unlike the other @sc{gnu} development
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tools, which must be configured for one or the other). Use @samp{-EB}
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to select big-endian output, and @samp{-EL} for little-endian.
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@cindex @code{-nocpp} ignored (MIPS)
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@item -nocpp
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This option is ignored. It is accepted for command-line compatibility with
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other assemblers, which use it to turn off C style preprocessing. With
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@sc{gnu} @code{@value{AS}}, there is no need for @samp{-nocpp}, because the
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@sc{gnu} assembler itself never runs the C preprocessor.
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@end table
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@node MIPS Object
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@section MIPS ECOFF object code
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@cindex ECOFF sections
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@cindex MIPS ECOFF sections
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Assembling for a @sc{mips} @sc{ecoff} target supports some additional sections
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besides the usual @code{.text}, @code{.data} and @code{.bss}. The
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additional sections are @code{.rdata}, used for read-only data,
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@code{.sdata}, used for small data, and @code{.sbss}, used for small
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common objects.
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When assembling for ECOFF, the assembler automatically uses the @code{$gp}
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(@code{$28}) register when forming the address of a small object. Any object
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in the @code{.sdata} or @code{.sbss} sections is considered ``small''. For
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external objects or objects in the @code{.bss} section, you may use the
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@samp{-G} option to control the size of objects for which the @code{$gp}
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register is used; the default value is 8, meaning that a reference to any
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object eight bytes or smaller uses @code{$gp}. Passing @samp{-G 0} to
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@value{AS} prevents it from using the @code{$gp} register at all. The size of
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an object in the @code{.bss} section is set by the @code{.comm} or
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@code{.lcomm} directive that defines it. The size of an external object may be
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set using the @code{.extern} directive. For example, @samp{.extern sym,4}
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declares that the object at @code{sym} is 4 bytes in length, while leaving
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@code{sym} otherwise undefined.
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@cindex small objects, MIPS ECOFF
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@cindex @code{gp} register, MIPS
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When assembling for @sc{ecoff}, the assembler uses the @code{$gp} (@code{$28})
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register to form the address of a ``small object''. Any object in the
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@code{.sdata} or @code{.sbss} sections is considered ``small'' in this sense.
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For external objects, or for objects in the @code{.bss} section, you can use
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the @sc{gcc} @samp{-G} option to control the size of objects addressed via
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@code{$gp}; the default value is 8, meaning that a reference to any object
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eight bytes or smaller uses @code{$gp}. Passing @samp{-G 0} to
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@code{@value{AS}} prevents it from using the @code{$gp} register on the basis
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of object size (but the assembler uses @code{$gp} for objects in @code{.sdata}
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or @code{sbss} in any case). The size of an object in the @code{.bss} section
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is set by the @code{.comm} or @code{.lcomm} directive that defines it. The
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size of an external object may be set with the @code{.extern} directive. For
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example, @samp{.extern sym,4} declares that the object at @code{sym} is 4 bytes
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in length, whie leaving @code{sym} otherwise undefined.
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Using small ECOFF objects requires linker support, and assumes that the
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@code{$gp} register was initialized correctly (normally done automatically
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by the startup code). MIPS ECOFF assembly code must avoid modifying the
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Using small @sc{ecoff} objects requires linker support, and assumes that the
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@code{$gp} register is correctly initialized (normally done automatically by
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the startup code). @sc{mips} @sc{ecoff} assembly code must not modify the
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@code{$gp} register.
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MIPS ECOFF @code{@value{AS}} supports several directives used for generating
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debugging information which are not support by traditional MIPS
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assemblers. These are @code{.def}, @code{.endef}, @code{.dim},
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@code{.file}, @code{.scl}, @code{.size}, @code{.tag}, @code{.type},
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@code{.val}, @code{.stabd}, @code{.stabn}, and @code{.stabs}. The
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debugging information generated by the three @code{.stab} directives can
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only be read by GDB, not by traditional MIPS debuggers (this enhancement
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is required to fully support C++ debugging). These directives are
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primarily used by compilers, not assembly language programmers, and are
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described elsewhere in this manual.
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@node MIPS Stabs
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@section Directives for debugging information
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@cindex MIPS debugging directives
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@sc{mips} @sc{ecoff} @code{@value{AS}} supports several directives used for
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generating debugging information which are not support by traditional @sc{mips}
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assemblers. These are @code{.def}, @code{.endef}, @code{.dim}, @code{.file},
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@code{.scl}, @code{.size}, @code{.tag}, @code{.type}, @code{.val},
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@code{.stabd}, @code{.stabn}, and @code{.stabs}. The debugging information
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generated by the three @code{.stab} directives can only be read by @sc{gdb},
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not by traditional @sc{mips} debuggers (this enhancement is required to fully
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support C++ debugging). These directives are primarily used by compilers, not
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assembly language programmers!
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@node MIPS Missing
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@section Missing instructions
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@cindex MIPS missing instructions
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@cindex missing instructions, MIPS
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Not all traditional @sc{mips} instructions are currently supported.
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Specifically, @code{li.d} and @code{li.s} are not currently supported.
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@end ifset
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@ifset GENERIC
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