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diff --git a/gas/doc/c-vax.texi b/gas/doc/c-vax.texi new file mode 100644 index 0000000000..b13d7e5a49 --- /dev/null +++ b/gas/doc/c-vax.texi @@ -0,0 +1,357 @@ +@c Copyright (C) 1991, 92, 93, 94, 95, 96, 1998 Free Software Foundation, Inc. +@c This is part of the GAS manual. +@c For copying conditions, see the file as.texinfo. +@c VAX/VMS description exhanced and corrected by Klaus K"aempf, kkaempf@progis.de +@ifset GENERIC +@node Vax-Dependent +@chapter VAX Dependent Features +@cindex VAX support + +@end ifset +@ifclear GENERIC +@node Machine Dependencies +@chapter VAX Dependent Features +@cindex VAX support + +@end ifclear + +@menu +* VAX-Opts:: VAX Command-Line Options +* VAX-float:: VAX Floating Point +* VAX-directives:: Vax Machine Directives +* VAX-opcodes:: VAX Opcodes +* VAX-branch:: VAX Branch Improvement +* VAX-operands:: VAX Operands +* VAX-no:: Not Supported on VAX +@end menu + + +@node VAX-Opts +@section VAX Command-Line Options + +@cindex command-line options ignored, VAX +@cindex VAX command-line options ignored +The Vax version of @code{@value{AS}} accepts any of the following options, +gives a warning message that the option was ignored and proceeds. +These options are for compatibility with scripts designed for other +people's assemblers. + +@table @code +@cindex @code{-D}, ignored on VAX +@cindex @code{-S}, ignored on VAX +@cindex @code{-T}, ignored on VAX +@item @code{-D} (Debug) +@itemx @code{-S} (Symbol Table) +@itemx @code{-T} (Token Trace) +These are obsolete options used to debug old assemblers. + +@cindex @code{-d}, VAX option +@item @code{-d} (Displacement size for JUMPs) +This option expects a number following the @samp{-d}. Like options +that expect filenames, the number may immediately follow the +@samp{-d} (old standard) or constitute the whole of the command line +argument that follows @samp{-d} (@sc{gnu} standard). + +@cindex @code{-V}, redundant on VAX +@item @code{-V} (Virtualize Interpass Temporary File) +Some other assemblers use a temporary file. This option +commanded them to keep the information in active memory rather +than in a disk file. @code{@value{AS}} always does this, so this +option is redundant. + +@cindex @code{-J}, ignored on VAX +@item @code{-J} (JUMPify Longer Branches) +Many 32-bit computers permit a variety of branch instructions +to do the same job. Some of these instructions are short (and +fast) but have a limited range; others are long (and slow) but +can branch anywhere in virtual memory. Often there are 3 +flavors of branch: short, medium and long. Some other +assemblers would emit short and medium branches, unless told by +this option to emit short and long branches. + +@cindex @code{-t}, ignored on VAX +@item @code{-t} (Temporary File Directory) +Some other assemblers may use a temporary file, and this option +takes a filename being the directory to site the temporary +file. Since @code{@value{AS}} does not use a temporary disk file, this +option makes no difference. @samp{-t} needs exactly one +filename. +@end table + +@cindex VMS (VAX) options +@cindex options for VAX/VMS +@cindex VAX/VMS options +@cindex Vax-11 C compatibility +@cindex symbols with uppercase, VAX/VMS +The Vax version of the assembler accepts additional options when +compiled for VMS: + +@table @samp +@cindex @samp{-h} option, VAX/VMS +@item -h @var{n} +External symbol or section (used for global variables) names are not +case sensitive on VAX/VMS and always mapped to upper case. This is +contrary to the C language definition which explicitly distinguishes +upper and lower case. To implement a standard conforming C compiler, +names must be changed (mapped) to preserve the case information. The +default mapping is to convert all lower case characters to uppercase and +adding an underscore followed by a 6 digit hex value, representing a 24 +digit binary value. The one digits in the binary value represent which +characters are uppercase in the original symbol name. + +The @samp{-h @var{n}} option determines how we map names. This takes +several values. No @samp{-h} switch at all allows case hacking as +described above. A value of zero (@samp{-h0}) implies names should be +upper case, and inhibits the case hack. A value of 2 (@samp{-h2}) +implies names should be all lower case, with no case hack. A value of 3 +(@samp{-h3}) implies that case should be preserved. The value 1 is +unused. The @code{-H} option directs @code{@value{AS}} to display +every mapped symbol during assembly. + +Symbols whose names include a dollar sign @samp{$} are exceptions to the +general name mapping. These symbols are normally only used to reference +VMS library names. Such symbols are always mapped to upper case. + +@cindex @samp{-+} option, VAX/VMS +@item -+ +The @samp{-+} option causes @code{@value{AS}} to truncate any symbol +name larger than 31 characters. The @samp{-+} option also prevents some +code following the @samp{_main} symbol normally added to make the object +file compatible with Vax-11 "C". + +@cindex @samp{-1} option, VAX/VMS +@item -1 +This option is ignored for backward compatibility with @code{@value{AS}} +version 1.x. + +@cindex @samp{-H} option, VAX/VMS +@item -H +The @samp{-H} option causes @code{@value{AS}} to print every symbol +which was changed by case mapping. +@end table + +@node VAX-float +@section VAX Floating Point + +@cindex VAX floating point +@cindex floating point, VAX +Conversion of flonums to floating point is correct, and +compatible with previous assemblers. Rounding is +towards zero if the remainder is exactly half the least significant bit. + +@code{D}, @code{F}, @code{G} and @code{H} floating point formats +are understood. + +Immediate floating literals (@emph{e.g.} @samp{S`$6.9}) +are rendered correctly. Again, rounding is towards zero in the +boundary case. + +@cindex @code{float} directive, VAX +@cindex @code{double} directive, VAX +The @code{.float} directive produces @code{f} format numbers. +The @code{.double} directive produces @code{d} format numbers. + +@node VAX-directives +@section Vax Machine Directives + +@cindex machine directives, VAX +@cindex VAX machine directives +The Vax version of the assembler supports four directives for +generating Vax floating point constants. They are described in the +table below. + +@cindex wide floating point directives, VAX +@table @code +@cindex @code{dfloat} directive, VAX +@item .dfloat +This expects zero or more flonums, separated by commas, and +assembles Vax @code{d} format 64-bit floating point constants. + +@cindex @code{ffloat} directive, VAX +@item .ffloat +This expects zero or more flonums, separated by commas, and +assembles Vax @code{f} format 32-bit floating point constants. + +@cindex @code{gfloat} directive, VAX +@item .gfloat +This expects zero or more flonums, separated by commas, and +assembles Vax @code{g} format 64-bit floating point constants. + +@cindex @code{hfloat} directive, VAX +@item .hfloat +This expects zero or more flonums, separated by commas, and +assembles Vax @code{h} format 128-bit floating point constants. + +@end table + +@node VAX-opcodes +@section VAX Opcodes + +@cindex VAX opcode mnemonics +@cindex opcode mnemonics, VAX +@cindex mnemonics for opcodes, VAX +All DEC mnemonics are supported. Beware that @code{case@dots{}} +instructions have exactly 3 operands. The dispatch table that +follows the @code{case@dots{}} instruction should be made with +@code{.word} statements. This is compatible with all unix +assemblers we know of. + +@node VAX-branch +@section VAX Branch Improvement + +@cindex VAX branch improvement +@cindex branch improvement, VAX +@cindex pseudo-ops for branch, VAX +Certain pseudo opcodes are permitted. They are for branch +instructions. They expand to the shortest branch instruction that +reaches the target. Generally these mnemonics are made by +substituting @samp{j} for @samp{b} at the start of a DEC mnemonic. +This feature is included both for compatibility and to help +compilers. If you do not need this feature, avoid these +opcodes. Here are the mnemonics, and the code they can expand into. + +@table @code +@item jbsb +@samp{Jsb} is already an instruction mnemonic, so we chose @samp{jbsb}. +@table @asis +@item (byte displacement) +@kbd{bsbb @dots{}} +@item (word displacement) +@kbd{bsbw @dots{}} +@item (long displacement) +@kbd{jsb @dots{}} +@end table +@item jbr +@itemx jr +Unconditional branch. +@table @asis +@item (byte displacement) +@kbd{brb @dots{}} +@item (word displacement) +@kbd{brw @dots{}} +@item (long displacement) +@kbd{jmp @dots{}} +@end table +@item j@var{COND} +@var{COND} may be any one of the conditional branches +@code{neq}, @code{nequ}, @code{eql}, @code{eqlu}, @code{gtr}, +@code{geq}, @code{lss}, @code{gtru}, @code{lequ}, @code{vc}, @code{vs}, +@code{gequ}, @code{cc}, @code{lssu}, @code{cs}. +@var{COND} may also be one of the bit tests +@code{bs}, @code{bc}, @code{bss}, @code{bcs}, @code{bsc}, @code{bcc}, +@code{bssi}, @code{bcci}, @code{lbs}, @code{lbc}. +@var{NOTCOND} is the opposite condition to @var{COND}. +@table @asis +@item (byte displacement) +@kbd{b@var{COND} @dots{}} +@item (word displacement) +@kbd{b@var{NOTCOND} foo ; brw @dots{} ; foo:} +@item (long displacement) +@kbd{b@var{NOTCOND} foo ; jmp @dots{} ; foo:} +@end table +@item jacb@var{X} +@var{X} may be one of @code{b d f g h l w}. +@table @asis +@item (word displacement) +@kbd{@var{OPCODE} @dots{}} +@item (long displacement) +@example +@var{OPCODE} @dots{}, foo ; +brb bar ; +foo: jmp @dots{} ; +bar: +@end example +@end table +@item jaob@var{YYY} +@var{YYY} may be one of @code{lss leq}. +@item jsob@var{ZZZ} +@var{ZZZ} may be one of @code{geq gtr}. +@table @asis +@item (byte displacement) +@kbd{@var{OPCODE} @dots{}} +@item (word displacement) +@example +@var{OPCODE} @dots{}, foo ; +brb bar ; +foo: brw @var{destination} ; +bar: +@end example +@item (long displacement) +@example +@var{OPCODE} @dots{}, foo ; +brb bar ; +foo: jmp @var{destination} ; +bar: +@end example +@end table +@item aobleq +@itemx aoblss +@itemx sobgeq +@itemx sobgtr +@table @asis +@item (byte displacement) +@kbd{@var{OPCODE} @dots{}} +@item (word displacement) +@example +@var{OPCODE} @dots{}, foo ; +brb bar ; +foo: brw @var{destination} ; +bar: +@end example +@item (long displacement) +@example +@var{OPCODE} @dots{}, foo ; +brb bar ; +foo: jmp @var{destination} ; +bar: +@end example +@end table +@end table + +@node VAX-operands +@section VAX Operands + +@cindex VAX operand notation +@cindex operand notation, VAX +@cindex immediate character, VAX +@cindex VAX immediate character +The immediate character is @samp{$} for Unix compatibility, not +@samp{#} as DEC writes it. + +@cindex indirect character, VAX +@cindex VAX indirect character +The indirect character is @samp{*} for Unix compatibility, not +@samp{@@} as DEC writes it. + +@cindex displacement sizing character, VAX +@cindex VAX displacement sizing character +The displacement sizing character is @samp{`} (an accent grave) for +Unix compatibility, not @samp{^} as DEC writes it. The letter +preceding @samp{`} may have either case. @samp{G} is not +understood, but all other letters (@code{b i l s w}) are understood. + +@cindex register names, VAX +@cindex VAX register names +Register names understood are @code{r0 r1 r2 @dots{} r15 ap fp sp +pc}. Upper and lower case letters are equivalent. + +For instance +@smallexample +tstb *w`$4(r5) +@end smallexample + +Any expression is permitted in an operand. Operands are comma +separated. + +@c There is some bug to do with recognizing expressions +@c in operands, but I forget what it is. It is +@c a syntax clash because () is used as an address mode +@c and to encapsulate sub-expressions. + +@node VAX-no +@section Not Supported on VAX + +@cindex VAX bitfields not supported +@cindex bitfields, not supported on VAX +Vax bit fields can not be assembled with @code{@value{AS}}. Someone +can add the required code if they really need it. |