bfd/

[deliverable/binutils-gdb.git] / gas / doc / c-mips.texi

diff --git a/gas/doc/c-mips.texi b/gas/doc/c-mips.texi
index 523dda3799f1730dcdde0d7a3aaf4ed9ed7aed59..974a3f097de133d62f0e98e3842318bfc016d0fd 100644 (file)
--- a/gas/doc/c-mips.texi
+++ b/gas/doc/c-mips.texi
@@ -1,4 +1,6 @@
-@c Copyright (C) 1991, 92, 93, 94, 95, 1997 Free Software Foundation, Inc.
+@c Copyright 1991, 1992, 1993, 1994, 1995, 1997, 1999, 2000, 2001,
+@c 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010
+@c Free Software Foundation, Inc.

 @c This is part of the GAS manual.
 @c For copying conditions, see the file as.texinfo.
 @ifset GENERIC
 @c This is part of the GAS manual.
 @c For copying conditions, see the file as.texinfo.
 @ifset GENERIC


@@ -13,20 +15,24 @@
 
 @cindex MIPS processor
 @sc{gnu} @code{@value{AS}} for @sc{mips} architectures supports several
 
 @cindex MIPS processor
 @sc{gnu} @code{@value{AS}} for @sc{mips} architectures supports several

-different @sc{mips} processors, and MIPS ISA levels I through IV.  For
-information about the @sc{mips} instruction set, see @cite{MIPS RISC
-Architecture}, by Kane and Heindrich (Prentice-Hall).  For an overview
-of @sc{mips} assembly conventions, see ``Appendix D: Assembly Language
-Programming'' in the same work.
+different @sc{mips} processors, and MIPS ISA levels I through V, MIPS32,
+and MIPS64.  For information about the @sc{mips} instruction set, see
+@cite{MIPS RISC Architecture}, by Kane and Heindrich (Prentice-Hall).
+For an overview of @sc{mips} assembly conventions, see ``Appendix D:
+Assembly Language Programming'' in the same work.

 
 @menu
 * MIPS Opts::          Assembler options
 * MIPS Object::        ECOFF object code
 * MIPS Stabs::         Directives for debugging information
 * MIPS ISA::           Directives to override the ISA level
 
 @menu
 * MIPS Opts::          Assembler options
 * MIPS Object::        ECOFF object code
 * MIPS Stabs::         Directives for debugging information
 * MIPS ISA::           Directives to override the ISA level

+* MIPS symbol sizes::   Directives to override the size of symbols

 * MIPS autoextend::    Directives for extending MIPS 16 bit instructions
 * MIPS insn::          Directive to mark data as an instruction
 * MIPS option stack::  Directives to save and restore options
 * MIPS autoextend::    Directives for extending MIPS 16 bit instructions
 * MIPS insn::          Directive to mark data as an instruction
 * MIPS option stack::  Directives to save and restore options

+* MIPS ASE instruction generation overrides:: Directives to control
+                       generation of MIPS ASE instructions
+* MIPS floating-point:: Directives to override floating-point options

 @end menu
 
 @node MIPS Opts
 @end menu
 
 @node MIPS Opts


@@ -55,24 +61,150 @@ little-endian output at run time (unlike the other @sc{gnu} development
 tools, which must be configured for one or the other).  Use @samp{-EB}
 to select big-endian output, and @samp{-EL} for little-endian.
 
 tools, which must be configured for one or the other).  Use @samp{-EB}
 to select big-endian output, and @samp{-EL} for little-endian.
 

+@item -KPIC
+@cindex PIC selection, MIPS
+@cindex @option{-KPIC} option, MIPS
+Generate SVR4-style PIC.  This option tells the assembler to generate
+SVR4-style position-independent macro expansions.  It also tells the
+assembler to mark the output file as PIC.
+
+@item -mvxworks-pic
+@cindex @option{-mvxworks-pic} option, MIPS
+Generate VxWorks PIC.  This option tells the assembler to generate
+VxWorks-style position-independent macro expansions.
+

 @cindex MIPS architecture options
 @item -mips1
 @itemx -mips2
 @itemx -mips3
 @itemx -mips4
 @cindex MIPS architecture options
 @item -mips1
 @itemx -mips2
 @itemx -mips3
 @itemx -mips4

+@itemx -mips5xo
+@itemx -mips32
+@itemx -mips32r2
+@itemx -mips64
+@itemx -mips64r2

 Generate code for a particular MIPS Instruction Set Architecture level.
 @samp{-mips1} corresponds to the @sc{r2000} and @sc{r3000} processors,
 @samp{-mips2} to the @sc{r6000} processor, @samp{-mips3} to the
 @sc{r4000} processor, and @samp{-mips4} to the @sc{r8000} and
 Generate code for a particular MIPS Instruction Set Architecture level.
 @samp{-mips1} corresponds to the @sc{r2000} and @sc{r3000} processors,
 @samp{-mips2} to the @sc{r6000} processor, @samp{-mips3} to the
 @sc{r4000} processor, and @samp{-mips4} to the @sc{r8000} and

-@sc{r10000} processors.  You can also switch instruction sets during the
-assembly; see @ref{MIPS ISA,, Directives to override the ISA level}.
+@sc{r10000} processors.  @samp{-mips5}, @samp{-mips32}, @samp{-mips32r2},
+@samp{-mips64}, and @samp{-mips64r2}
+correspond to generic
+@sc{MIPS V}, @sc{MIPS32}, @sc{MIPS32 Release 2}, @sc{MIPS64},
+and @sc{MIPS64 Release 2}
+ISA processors, respectively.  You can also switch
+instruction sets during the assembly; see @ref{MIPS ISA, Directives to
+override the ISA level}.
+
+@item -mgp32
+@itemx -mfp32
+Some macros have different expansions for 32-bit and 64-bit registers.
+The register sizes are normally inferred from the ISA and ABI, but these
+flags force a certain group of registers to be treated as 32 bits wide at
+all times.  @samp{-mgp32} controls the size of general-purpose registers
+and @samp{-mfp32} controls the size of floating-point registers.
+
+The @code{.set gp=32} and @code{.set fp=32} directives allow the size
+of registers to be changed for parts of an object. The default value is
+restored by @code{.set gp=default} and @code{.set fp=default}.
+
+On some MIPS variants there is a 32-bit mode flag; when this flag is
+set, 64-bit instructions generate a trap.  Also, some 32-bit OSes only
+save the 32-bit registers on a context switch, so it is essential never
+to use the 64-bit registers.
+
+@item -mgp64
+@itemx -mfp64
+Assume that 64-bit registers are available.  This is provided in the
+interests of symmetry with @samp{-mgp32} and @samp{-mfp32}.
+
+The @code{.set gp=64} and @code{.set fp=64} directives allow the size
+of registers to be changed for parts of an object. The default value is
+restored by @code{.set gp=default} and @code{.set fp=default}.

 
 @item -mips16
 @itemx -no-mips16
 Generate code for the MIPS 16 processor.  This is equivalent to putting
 
 @item -mips16
 @itemx -no-mips16
 Generate code for the MIPS 16 processor.  This is equivalent to putting

-@samp{.set mips16} at the start of the assembly file.  @samp{-no-mips16}
+@code{.set mips16} at the start of the assembly file.  @samp{-no-mips16}

 turns off this option.
 
 turns off this option.
 

+@item -msmartmips
+@itemx -mno-smartmips
+Enables the SmartMIPS extensions to the MIPS32 instruction set, which
+provides a number of new instructions which target smartcard and
+cryptographic applications.  This is equivalent to putting
+@code{.set smartmips} at the start of the assembly file.
+@samp{-mno-smartmips} turns off this option.
+
+@item -mips3d
+@itemx -no-mips3d
+Generate code for the MIPS-3D Application Specific Extension.
+This tells the assembler to accept MIPS-3D instructions.
+@samp{-no-mips3d} turns off this option.
+
+@item -mdmx
+@itemx -no-mdmx
+Generate code for the MDMX Application Specific Extension.
+This tells the assembler to accept MDMX instructions.
+@samp{-no-mdmx} turns off this option.
+
+@item -mdsp
+@itemx -mno-dsp
+Generate code for the DSP Release 1 Application Specific Extension.
+This tells the assembler to accept DSP Release 1 instructions.
+@samp{-mno-dsp} turns off this option.
+
+@item -mdspr2
+@itemx -mno-dspr2
+Generate code for the DSP Release 2 Application Specific Extension.
+This option implies -mdsp.
+This tells the assembler to accept DSP Release 2 instructions.
+@samp{-mno-dspr2} turns off this option.
+
+@item -mmt
+@itemx -mno-mt
+Generate code for the MT Application Specific Extension.
+This tells the assembler to accept MT instructions.
+@samp{-mno-mt} turns off this option.
+
+@item -mfix7000
+@itemx -mno-fix7000
+Cause nops to be inserted if the read of the destination register
+of an mfhi or mflo instruction occurs in the following two instructions.
+
+@item -mfix-loongson2f-jump
+@itemx -mno-fix-loongson2f-jump
+Eliminate instruction fetch from outside 256M region to work around the
+Loongson2F @samp{jump} instructions.  Without it, under extreme cases,
+the kernel may crash.  The issue has been solved in latest processor
+batches, but this fix has no side effect to them.
+
+@item -mfix-loongson2f-nop
+@itemx -mno-fix-loongson2f-nop
+Replace nops by @code{or at,at,zero} to work around the Loongson2F
+@samp{nop} errata.  Without it, under extreme cases, cpu might
+deadlock.  The issue has been solved in latest loongson2f batches, but
+this fix has no side effect to them.
+
+@item -mfix-vr4120
+@itemx -mno-fix-vr4120
+Insert nops to work around certain VR4120 errata.  This option is
+intended to be used on GCC-generated code: it is not designed to catch
+all problems in hand-written assembler code.
+
+@item -mfix-vr4130
+@itemx -mno-fix-vr4130
+Insert nops to work around the VR4130 @samp{mflo}/@samp{mfhi} errata.
+
+@item -mfix-24k
+@itemx -no-mfix-24k
+Insert nops to work around the 24K @samp{eret}/@samp{deret} errata.
+
+@item -mfix-cn63xxp1
+@itemx -mno-fix-cn63xxp1
+Replace @code{pref} hints 0 - 4 and 6 - 24 with hint 28 to work around
+certain CN63XXP1 errata.
+

 @item -m4010
 @itemx -no-m4010
 Generate code for the LSI @sc{r4010} chip.  This tells the assembler to
 @item -m4010
 @itemx -no-m4010
 Generate code for the LSI @sc{r4010} chip.  This tells the assembler to


@@ -96,7 +228,7 @@ For each option @samp{-m@var{nnnn}}, generate code for the MIPS
 @sc{r@var{nnnn}} chip.  This tells the assembler to accept instructions
 specific to that chip, and to schedule for that chip's hazards.
 
 @sc{r@var{nnnn}} chip.  This tells the assembler to accept instructions
 specific to that chip, and to schedule for that chip's hazards.
 

-@item -mcpu=@var{cpu}
+@item -march=@var{cpu}

 Generate code for a particular MIPS cpu.  It is exactly equivalent to
 @samp{-m@var{cpu}}, except that there are more value of @var{cpu}
 understood.  Valid @var{cpu} value are:
 Generate code for a particular MIPS cpu.  It is exactly equivalent to
 @samp{-m@var{cpu}}, except that there are more value of @var{cpu}
 understood.  Valid @var{cpu} value are:


@@ -109,16 +241,91 @@ understood.  Valid @var{cpu} value are:
 4010,
 4100,
 4111,
 4010,
 4100,
 4111,

+vr4120,
+vr4130,
+vr4181,

 4300,
 4400,
 4600,
 4650,
 5000,
 4300,
 4400,
 4600,
 4650,
 5000,

+rm5200,
+rm5230,
+rm5231,
+rm5261,
+rm5721,
+vr5400,
+vr5500,

 6000,
 6000,

+rm7000,

 8000,
 8000,

-10000
+rm9000,
+10000,
+12000,
+14000,
+16000,
+4kc,
+4km,
+4kp,
+4ksc,
+4kec,
+4kem,
+4kep,
+4ksd,
+m4k,
+m4kp,
+24kc,
+24kf2_1,
+24kf,
+24kf1_1,
+24kec,
+24kef2_1,
+24kef,
+24kef1_1,
+34kc,
+34kf2_1,
+34kf,
+34kf1_1,
+74kc,
+74kf2_1,
+74kf,
+74kf1_1,
+74kf3_2,
+1004kc,
+1004kf2_1,
+1004kf,
+1004kf1_1,
+5kc,
+5kf,
+20kc,
+25kf,
+sb1,
+sb1a,
+loongson2e,
+loongson2f,
+loongson3a,
+octeon,
+xlr

 @end quotation
 
 @end quotation
 

+For compatibility reasons, @samp{@var{n}x} and @samp{@var{b}fx} are
+accepted as synonyms for @samp{@var{n}f1_1}.  These values are
+deprecated.
+
+@item -mtune=@var{cpu}
+Schedule and tune for a particular MIPS cpu.  Valid @var{cpu} values are
+identical to @samp{-march=@var{cpu}}.
+
+@item -mabi=@var{abi}
+Record which ABI the source code uses.  The recognized arguments
+are: @samp{32}, @samp{n32}, @samp{o64}, @samp{64} and @samp{eabi}.
+
+@item -msym32
+@itemx -mno-sym32
+@cindex -msym32
+@cindex -mno-sym32
+Equivalent to adding @code{.set sym32} or @code{.set nosym32} to
+the beginning of the assembler input.  @xref{MIPS symbol sizes}.

 
 @cindex @code{-nocpp} ignored (MIPS)
 @item -nocpp
 
 @cindex @code{-nocpp} ignored (MIPS)
 @item -nocpp


@@ -127,6 +334,32 @@ other assemblers, which use it to turn off C style preprocessing.  With
 @sc{gnu} @code{@value{AS}}, there is no need for @samp{-nocpp}, because the
 @sc{gnu} assembler itself never runs the C preprocessor.
 
 @sc{gnu} @code{@value{AS}}, there is no need for @samp{-nocpp}, because the
 @sc{gnu} assembler itself never runs the C preprocessor.
 

+@item -msoft-float
+@itemx -mhard-float
+Disable or enable floating-point instructions.  Note that by default
+floating-point instructions are always allowed even with CPU targets
+that don't have support for these instructions.
+
+@item -msingle-float
+@itemx -mdouble-float
+Disable or enable double-precision floating-point operations.  Note
+that by default double-precision floating-point operations are always
+allowed even with CPU targets that don't have support for these
+operations.
+
+@item --construct-floats
+@itemx --no-construct-floats
+The @code{--no-construct-floats} option disables the construction of
+double width floating point constants by loading the two halves of the
+value into the two single width floating point registers that make up
+the double width register.  This feature is useful if the processor
+support the FR bit in its status  register, and this bit is known (by
+the programmer) to be set.  This bit prevents the aliasing of the double
+width register by the single width registers.
+
+By default @code{--construct-floats} is selected, allowing construction
+of these floating point constants.
+

 @item --trap
 @itemx --no-break
 @c FIXME!  (1) reflect these options (next item too) in option summaries;
 @item --trap
 @itemx --no-break
 @c FIXME!  (1) reflect these options (next item too) in option summaries;


@@ -141,6 +374,21 @@ are only supported at Instruction Set Architecture level 2 and higher.
 @itemx --no-trap
 Generate code to take a break exception rather than a trap exception when an
 error is detected.  This is the default.
 @itemx --no-trap
 Generate code to take a break exception rather than a trap exception when an
 error is detected.  This is the default.

+
+@item -mpdr
+@itemx -mno-pdr
+Control generation of @code{.pdr} sections.  Off by default on IRIX, on
+elsewhere.
+
+@item -mshared
+@itemx -mno-shared
+When generating code using the Unix calling conventions (selected by
+@samp{-KPIC} or @samp{-mcall_shared}), gas will normally generate code
+which can go into a shared library.  The @samp{-mno-shared} option
+tells gas to generate code which uses the calling convention, but can
+not go into a shared library.  The resulting code is slightly more
+efficient.  This option only affects the handling of the
+@samp{.cpload} and @samp{.cpsetup} pseudo-ops.

 @end table
 
 @node MIPS Object
 @end table
 
 @node MIPS Object


@@ -190,6 +438,61 @@ not by traditional @sc{mips} debuggers (this enhancement is required to fully
 support C++ debugging).  These directives are primarily used by compilers, not
 assembly language programmers!
 
 support C++ debugging).  These directives are primarily used by compilers, not
 assembly language programmers!
 

+@node MIPS symbol sizes
+@section Directives to override the size of symbols
+
+@cindex @code{.set sym32}
+@cindex @code{.set nosym32}
+The n64 ABI allows symbols to have any 64-bit value.  Although this
+provides a great deal of flexibility, it means that some macros have
+much longer expansions than their 32-bit counterparts.  For example,
+the non-PIC expansion of @samp{dla $4,sym} is usually:
+
+@smallexample
+lui     $4,%highest(sym)
+lui     $1,%hi(sym)
+daddiu  $4,$4,%higher(sym)
+daddiu  $1,$1,%lo(sym)
+dsll32  $4,$4,0
+daddu   $4,$4,$1
+@end smallexample
+
+whereas the 32-bit expansion is simply:
+
+@smallexample
+lui     $4,%hi(sym)
+daddiu  $4,$4,%lo(sym)
+@end smallexample
+
+n64 code is sometimes constructed in such a way that all symbolic
+constants are known to have 32-bit values, and in such cases, it's
+preferable to use the 32-bit expansion instead of the 64-bit
+expansion.
+
+You can use the @code{.set sym32} directive to tell the assembler
+that, from this point on, all expressions of the form
+@samp{@var{symbol}} or @samp{@var{symbol} + @var{offset}}
+have 32-bit values.  For example:
+
+@smallexample
+.set sym32
+dla     $4,sym
+lw      $4,sym+16
+sw      $4,sym+0x8000($4)
+@end smallexample
+
+will cause the assembler to treat @samp{sym}, @code{sym+16} and
+@code{sym+0x8000} as 32-bit values.  The handling of non-symbolic
+addresses is not affected.
+
+The directive @code{.set nosym32} ends a @code{.set sym32} block and
+reverts to the normal behavior.  It is also possible to change the
+symbol size using the command-line options @option{-msym32} and
+@option{-mno-sym32}.
+
+These options and directives are always accepted, but at present,
+they have no effect for anything other than n64.
+

 @node MIPS ISA
 @section Directives to override the ISA level
 
 @node MIPS ISA
 @section Directives to override the ISA level
 


@@ -197,21 +500,31 @@ assembly language programmers!
 @kindex @code{.set mips@var{n}}
 @sc{gnu} @code{@value{AS}} supports an additional directive to change
 the @sc{mips} Instruction Set Architecture level on the fly: @code{.set
 @kindex @code{.set mips@var{n}}
 @sc{gnu} @code{@value{AS}} supports an additional directive to change
 the @sc{mips} Instruction Set Architecture level on the fly: @code{.set

-mips@var{n}}.  @var{n} should be a number from 0 to 4.  A value from 1
-to 4 makes the assembler accept instructions for the corresponding
-@sc{isa} level, from that point on in the assembly.  @code{.set
-mips@var{n}} affects not only which instructions are permitted, but also
-how certain macros are expanded.  @code{.set mips0} restores the
-@sc{isa} level to its original level: either the level you selected with
-command line options, or the default for your configuration.  You can
-use this feature to permit specific @sc{r4000} instructions while
-assembling in 32 bit mode.  Use this directive with care!
-
-The directive @samp{.set mips16} puts the assembler into MIPS 16 mode,
+mips@var{n}}.  @var{n} should be a number from 0 to 5, or 32, 32r2, 64
+or 64r2.
+The values other than 0 make the assembler accept instructions
+for the corresponding @sc{isa} level, from that point on in the
+assembly.  @code{.set mips@var{n}} affects not only which instructions
+are permitted, but also how certain macros are expanded.  @code{.set
+mips0} restores the @sc{isa} level to its original level: either the
+level you selected with command line options, or the default for your
+configuration.  You can use this feature to permit specific @sc{mips3}
+instructions while assembling in 32 bit mode.  Use this directive with
+care!
+
+@cindex MIPS CPU override
+@kindex @code{.set arch=@var{cpu}}
+The @code{.set arch=@var{cpu}} directive provides even finer control.
+It changes the effective CPU target and allows the assembler to use
+instructions specific to a particular CPU.  All CPUs supported by the
+@samp{-march} command line option are also selectable by this directive.
+The original value is restored by @code{.set arch=default}.
+
+The directive @code{.set mips16} puts the assembler into MIPS 16 mode,

 in which it will assemble instructions for the MIPS 16 processor.  Use
 in which it will assemble instructions for the MIPS 16 processor.  Use

-@samp{.set nomips16} to return to normal 32 bit mode.
+@code{.set nomips16} to return to normal 32 bit mode.

 
 

-Traditional @sc{mips} assemblers do not support this directive.  
+Traditional @sc{mips} assemblers do not support this directive.

 
 @node MIPS autoextend
 @section Directives for extending MIPS 16 bit instructions
 
 @node MIPS autoextend
 @section Directives for extending MIPS 16 bit instructions


@@ -219,10 +532,10 @@ Traditional @sc{mips} assemblers do not support this directive.
 @kindex @code{.set autoextend}
 @kindex @code{.set noautoextend}
 By default, MIPS 16 instructions are automatically extended to 32 bits
 @kindex @code{.set autoextend}
 @kindex @code{.set noautoextend}
 By default, MIPS 16 instructions are automatically extended to 32 bits

-when necessary.  The directive @samp{.set noautoextend} will turn this
-off.  When @samp{.set noautoextend} is in effect, any 32 bit instruction
-must be explicitly extended with the @samp{.e} modifier (e.g.,
-@samp{li.e $4,1000}).  The directive @samp{.set autoextend} may be used
+when necessary.  The directive @code{.set noautoextend} will turn this
+off.  When @code{.set noautoextend} is in effect, any 32 bit instruction
+must be explicitly extended with the @code{.e} modifier (e.g.,
+@code{li.e $4,1000}).  The directive @code{.set autoextend} may be used

 to once again automatically extend instructions when necessary.
 
 This directive is only meaningful when in MIPS 16 mode.  Traditional
 to once again automatically extend instructions when necessary.
 
 This directive is only meaningful when in MIPS 16 mode.  Traditional


@@ -238,6 +551,32 @@ when loading the address of a label which precedes instructions,
 @code{@value{AS}} automatically adds 1 to the value, so that jumping to
 the loaded address will do the right thing.
 
 @code{@value{AS}} automatically adds 1 to the value, so that jumping to
 the loaded address will do the right thing.
 

+@kindex @code{.global}
+The @code{.global} and @code{.globl} directives supported by
+@code{@value{AS}} will by default mark the symbol as pointing to a
+region of data not code.  This means that, for example, any
+instructions following such a symbol will not be disassembled by
+@code{objdump} as it will regard them as data.  To change this
+behaviour an optional section name can be placed after the symbol name
+in the @code{.global} directive.  If this section exists and is known
+to be a code section, then the symbol will be marked as poiting at
+code not data.  Ie the syntax for the directive is:
+
+  @code{.global @var{symbol}[ @var{section}][, @var{symbol}[ @var{section}]] ...},
+
+Here is a short example:
+
+@example
+        .global foo .text, bar, baz .data
+foo:
+        nop
+bar:
+        .word 0x0
+baz:
+        .word 0x1
+        
+@end example
+

 @node MIPS option stack
 @section Directives to save and restore options
 
 @node MIPS option stack
 @section Directives to save and restore options
 


@@ -255,3 +594,81 @@ option such as the ISA level or instruction reordering but does not want
 to change the state of the code which invoked the macro.
 
 Traditional @sc{mips} assemblers do not support these directives.
 to change the state of the code which invoked the macro.
 
 Traditional @sc{mips} assemblers do not support these directives.

+
+@node MIPS ASE instruction generation overrides
+@section Directives to control generation of MIPS ASE instructions
+
+@cindex MIPS MIPS-3D instruction generation override
+@kindex @code{.set mips3d}
+@kindex @code{.set nomips3d}
+The directive @code{.set mips3d} makes the assembler accept instructions
+from the MIPS-3D Application Specific Extension from that point on
+in the assembly.  The @code{.set nomips3d} directive prevents MIPS-3D
+instructions from being accepted.
+
+@cindex SmartMIPS instruction generation override
+@kindex @code{.set smartmips}
+@kindex @code{.set nosmartmips}
+The directive @code{.set smartmips} makes the assembler accept
+instructions from the SmartMIPS Application Specific Extension to the
+MIPS32 @sc{isa} from that point on in the assembly.  The
+@code{.set nosmartmips} directive prevents SmartMIPS instructions from
+being accepted.
+
+@cindex MIPS MDMX instruction generation override
+@kindex @code{.set mdmx}
+@kindex @code{.set nomdmx}
+The directive @code{.set mdmx} makes the assembler accept instructions
+from the MDMX Application Specific Extension from that point on
+in the assembly.  The @code{.set nomdmx} directive prevents MDMX
+instructions from being accepted.
+
+@cindex MIPS DSP Release 1 instruction generation override
+@kindex @code{.set dsp}
+@kindex @code{.set nodsp}
+The directive @code{.set dsp} makes the assembler accept instructions
+from the DSP Release 1 Application Specific Extension from that point
+on in the assembly.  The @code{.set nodsp} directive prevents DSP
+Release 1 instructions from being accepted.
+
+@cindex MIPS DSP Release 2 instruction generation override
+@kindex @code{.set dspr2}
+@kindex @code{.set nodspr2}
+The directive @code{.set dspr2} makes the assembler accept instructions
+from the DSP Release 2 Application Specific Extension from that point
+on in the assembly.  This dirctive implies @code{.set dsp}.  The
+@code{.set nodspr2} directive prevents DSP Release 2 instructions from
+being accepted.
+
+@cindex MIPS MT instruction generation override
+@kindex @code{.set mt}
+@kindex @code{.set nomt}
+The directive @code{.set mt} makes the assembler accept instructions
+from the MT Application Specific Extension from that point on
+in the assembly.  The @code{.set nomt} directive prevents MT
+instructions from being accepted.
+
+Traditional @sc{mips} assemblers do not support these directives.
+
+@node MIPS floating-point
+@section Directives to override floating-point options
+
+@cindex Disable floating-point instructions
+@kindex @code{.set softfloat}
+@kindex @code{.set hardfloat}
+The directives @code{.set softfloat} and @code{.set hardfloat} provide
+finer control of disabling and enabling float-point instructions.
+These directives always override the default (that hard-float
+instructions are accepted) or the command-line options
+(@samp{-msoft-float} and @samp{-mhard-float}).
+
+@cindex Disable single-precision floating-point operations
+@kindex @code{.set singlefloat}
+@kindex @code{.set doublefloat}
+The directives @code{.set singlefloat} and @code{.set doublefloat}
+provide finer control of disabling and enabling double-precision
+float-point operations.  These directives always override the default
+(that double-precision operations are accepted) or the command-line
+options (@samp{-msingle-float} and @samp{-mdouble-float}).
+
+Traditional @sc{mips} assemblers do not support these directives.