@c Copyright (C) 2001-2026 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 PDP-11-Dependent
@chapter PDP-11 Dependent Features
@end ifset
@ifclear GENERIC
@node Machine Dependencies
@chapter PDP-11 Dependent Features
@end ifclear

@cindex PDP-11 support

@menu
* PDP-11-Options::		Options
* PDP-11-Pseudos::		Assembler Directives
* PDP-11-Syntax::		DEC Syntax versus BSD Syntax
* PDP-11-Mnemonics::		Instruction Naming
* PDP-11-Synthetic::		Synthetic Instructions
@end menu

@node PDP-11-Options
@section Options

@cindex options for PDP-11

The PDP-11 version of @code{@value{AS}} has a rich set of machine
dependent options.

@subsection Code Generation Options

@table @code
@cindex -mpic
@cindex -mno-pic
@item -mpic | -mno-pic
Generate position-independent (or position-dependent) code.

The default is to generate position-independent code.
@end table

@subsection Instruction Set Extension Options

These options enables or disables the use of extensions over the base
line instruction set as introduced by the first PDP-11 CPU: the KA11.
Most options come in two variants: a @code{-m}@var{extension} that
enables @var{extension}, and a @code{-mno-}@var{extension} that disables
@var{extension}.

The default is to enable all extensions.

@table @code
@cindex -mall
@cindex -mall-extensions
@item -mall | -mall-extensions
Enable all instruction set extensions.

@cindex -mno-extensions
@item -mno-extensions
Disable all instruction set extensions.

@cindex -mcis
@cindex -mno-cis
@item -mcis | -mno-cis
Enable (or disable) the use of the commercial instruction set, which
consists of these instructions: @code{ADDNI}, @code{ADDN}, @code{ADDPI},
@code{ADDP}, @code{ASHNI}, @code{ASHN}, @code{ASHPI}, @code{ASHP},
@code{CMPCI}, @code{CMPC}, @code{CMPNI}, @code{CMPN}, @code{CMPPI},
@code{CMPP}, @code{CVTLNI}, @code{CVTLN}, @code{CVTLPI}, @code{CVTLP},
@code{CVTNLI}, @code{CVTNL}, @code{CVTNPI}, @code{CVTNP}, @code{CVTPLI},
@code{CVTPL}, @code{CVTPNI}, @code{CVTPN}, @code{DIVPI}, @code{DIVP},
@code{L2DR}, @code{L3DR}, @code{LOCCI}, @code{LOCC}, @code{MATCI},
@code{MATC}, @code{MOVCI}, @code{MOVC}, @code{MOVRCI}, @code{MOVRC},
@code{MOVTCI}, @code{MOVTC}, @code{MULPI}, @code{MULP}, @code{SCANCI},
@code{SCANC}, @code{SKPCI}, @code{SKPC}, @code{SPANCI}, @code{SPANC},
@code{SUBNI}, @code{SUBN}, @code{SUBPI}, and @code{SUBP}.

@cindex -mcsm
@cindex -mno-csm
@item -mcsm | -mno-csm
Enable (or disable) the use of the @code{CSM} instruction.

@cindex -meis
@cindex -mno-eis
@item -meis | -mno-eis
Enable (or disable) the use of the extended instruction set, which
consists of these instructions: @code{ASHC}, @code{ASH}, @code{DIV},
@code{MARK}, @code{MUL}, @code{RTT}, @code{SOB} @code{SXT}, and
@code{XOR}.

@cindex -mfis
@cindex -mno-fis
@cindex -mkev11
@cindex -mkev11
@cindex -mno-kev11
@item -mfis | -mkev11
@itemx -mno-fis | -mno-kev11
Enable (or disable) the use of the KEV11 floating-point instructions:
@code{FADD}, @code{FDIV}, @code{FMUL}, and @code{FSUB}.

@cindex -mfpp
@cindex -mno-fpp
@cindex -mfpu
@cindex -mno-fpu
@cindex -mfp-11
@cindex -mno-fp-11
@item -mfpp | -mfpu | -mfp-11
@itemx -mno-fpp | -mno-fpu | -mno-fp-11
Enable (or disable) the use of FP-11 floating-point instructions:
@code{ABSF}, @code{ADDF}, @code{CFCC}, @code{CLRF}, @code{CMPF},
@code{DIVF}, @code{LDCFF}, @code{LDCIF}, @code{LDEXP}, @code{LDF},
@code{LDFPS}, @code{MODF}, @code{MULF}, @code{NEGF}, @code{SETD},
@code{SETF}, @code{SETI}, @code{SETL}, @code{STCFF}, @code{STCFI},
@code{STEXP}, @code{STF}, @code{STFPS}, @code{STST}, @code{SUBF}, and
@code{TSTF}.

@cindex -mlimited-eis
@cindex -mno-limited-eis
@item -mlimited-eis | -mno-limited-eis
Enable (or disable) the use of the limited extended instruction set:
@code{MARK}, @code{RTT}, @code{SOB}, @code{SXT}, and @code{XOR}.

The -mno-limited-eis options also implies -mno-eis.

@cindex -mmfpt
@cindex -mno-mfpt
@item -mmfpt | -mno-mfpt
Enable (or disable) the use of the @code{MFPT} instruction.

@cindex -mmutiproc
@cindex -mno-mutiproc
@item -mmultiproc | -mno-multiproc
Enable (or disable) the use of multiprocessor instructions: @code{TSTSET} and
@code{WRTLCK}.

@cindex -mmxps
@cindex -mno-mxps
@item -mmxps | -mno-mxps
Enable (or disable) the use of the @code{MFPS} and @code{MTPS} instructions.

@cindex -mspl
@cindex -mno-spl
@item -mspl | -mno-spl
Enable (or disable) the use of the @code{SPL} instruction.

@cindex -mmicrocode
@cindex -mno-microcode
Enable (or disable) the use of the microcode instructions: @code{LDUB},
@code{MED}, and @code{XFC}.
@end table

@subsection CPU Model Options

These options enable the instruction set extensions supported by a
particular CPU, and disables all other extensions.

@table @code
@cindex -mka11
@item -mka11
KA11 CPU.  Base line instruction set only.

@cindex -mkb11
@item -mkb11
KB11 CPU.  Enable extended instruction set and @code{SPL}.

@cindex -mkd11a
@item -mkd11a
KD11-A CPU.  Enable limited extended instruction set.

@cindex -mkd11b
@item -mkd11b
KD11-B CPU.  Base line instruction set only.

@cindex -mkd11d
@item -mkd11d
KD11-D CPU.  Base line instruction set only.

@cindex -mkd11e
@item -mkd11e
KD11-E CPU.  Enable extended instruction set, @code{MFPS}, and @code{MTPS}.

@cindex -mkd11f
@cindex -mkd11h
@cindex -mkd11q
@item -mkd11f | -mkd11h | -mkd11q
KD11-F, KD11-H, or KD11-Q CPU.  Enable limited extended instruction set,
@code{MFPS}, and @code{MTPS}.

@cindex -mkd11k
@item -mkd11k
KD11-K CPU.  Enable extended instruction set, @code{LDUB}, @code{MED},
@code{MFPS}, @code{MFPT}, @code{MTPS}, and @code{XFC}.

@cindex -mkd11z
@item -mkd11z
KD11-Z CPU.  Enable extended instruction set, @code{CSM}, @code{MFPS},
@code{MFPT}, @code{MTPS}, and @code{SPL}.

@cindex -mf11
@item -mf11
F11 CPU.  Enable extended instruction set, @code{MFPS}, @code{MFPT}, and
@code{MTPS}.

@cindex -mj11
@item -mj11
J11 CPU.  Enable extended instruction set, @code{CSM}, @code{MFPS},
@code{MFPT}, @code{MTPS}, @code{SPL}, @code{TSTSET}, and @code{WRTLCK}.

@cindex -mt11
@item -mt11
T11 CPU.  Enable limited extended instruction set, @code{MFPS}, and
@code{MTPS}.
@end table

@subsection Machine Model Options

These options enable the instruction set extensions supported by a
particular machine model, and disables all other extensions.

@table @code
@cindex -m11/03
@item -m11/03
Same as @code{-mkd11f}.

@cindex -m11/04
@item -m11/04
Same as @code{-mkd11d}.

@cindex -m11/05
@cindex -m11/10
@item -m11/05 | -m11/10
Same as @code{-mkd11b}.

@cindex -m11/15
@cindex -m11/20
@item -m11/15 | -m11/20
Same as @code{-mka11}.

@cindex -m11/21
@item -m11/21
Same as @code{-mt11}.

@cindex -m11/23
@cindex -m11/24
@item -m11/23 | -m11/24
Same as @code{-mf11}.

@cindex -m11/34
@item -m11/34
Same as @code{-mkd11e}.

@cindex -m11/34a
@item -m11/34a
Ame as @code{-mkd11e} @code{-mfpp}.

@cindex -m11/35
@cindex -m11/40
@item -m11/35 | -m11/40
Same as @code{-mkd11a}.

@cindex -m11/44
@item -m11/44
Same as @code{-mkd11z}.

@cindex -m11/45
@cindex -m11/50
@cindex -m11/55
@cindex -m11/70
@item -m11/45 | -m11/50 | -m11/55 | -m11/70
Same as @code{-mkb11}.

@cindex -m11/53
@cindex -m11/73
@cindex -m11/83
@cindex -m11/84
@cindex -m11/93
@cindex -m11/94
@item -m11/53 | -m11/73 | -m11/83 | -m11/84 | -m11/93 | -m11/94
Same as @code{-mj11}.

@cindex -m11/60
@item -m11/60
Same as @code{-mkd11k}.
@end table

@node PDP-11-Pseudos
@section Assembler Directives

The PDP-11 version of @code{@value{AS}} has a few machine
dependent assembler directives.

@table @code
@item .bss
Switch to the @code{bss} section.

@item .even
Align the location counter to an even number.
@end table

@node PDP-11-Syntax
@section PDP-11 Assembly Language Syntax

@cindex PDP-11 syntax

@cindex DEC syntax
@cindex BSD syntax
@code{@value{AS}} supports both DEC syntax and BSD syntax.  The only
difference is that in DEC syntax, a @code{#} character is used to denote
an immediate constants, while in BSD syntax the character for this
purpose is @code{$}.

@cindex PDP-11 general-purpose register syntax
general-purpose registers are named @code{r0} through @code{r7}.
Mnemonic alternatives for @code{r6} and @code{r7} are @code{sp} and
@code{pc}, respectively.

@cindex PDP-11 floating-point register syntax
Floating-point registers are named @code{ac0} through @code{ac3}, or
alternatively @code{fr0} through @code{fr3}.

@cindex PDP-11 comments
Comments are started with a @code{#} or a @code{/} character, and extend
to the end of the line.  (FIXME: clash with immediates?)

@cindex PDP-11 line separator
Multiple statements on the same line can be separated by the @samp{;} character.

@node PDP-11-Mnemonics
@section Instruction Naming

@cindex PDP-11 instruction naming

Some instructions have alternative names.

@table @code
@item BCC
@code{BHIS}

@item BCS
@code{BLO}

@item L2DR
@code{L2D}

@item L3DR
@code{L3D}

@item SYS
@code{TRAP}
@end table

@node PDP-11-Synthetic
@section Synthetic Instructions

The @code{JBR} and @code{J}@var{CC} synthetic instructions are not
supported yet.
