freebsd-dev/gas/doc/c-i860.texi

@c Copyright 2000, 2003 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 i860-Dependent
@chapter Intel i860 Dependent Features
@end ifset
@ifclear GENERIC
@node Machine Dependencies
@chapter Intel i860 Dependent Features
@end ifclear

@ignore
@c FIXME: This is basically a stub for i860. There is tons more information
that I will add later (jle@cygnus.com).
@end ignore

@cindex i860 support
@menu
* Notes-i860::                  i860 Notes
* Options-i860::                i860 Command-line Options
* Directives-i860::             i860 Machine Directives
* Opcodes for i860::            i860 Opcodes
@end menu

@node Notes-i860
@section i860 Notes 
This is a fairly complete i860 assembler which is compatible with the
UNIX System V/860 Release 4 assembler. However, it does not currently
support SVR4 PIC (i.e., @code{@@GOT, @@GOTOFF, @@PLT}).

Like the SVR4/860 assembler, the output object format is ELF32. Currently,
this is the only supported object format. If there is sufficient interest,
other formats such as COFF may be implemented.

Both the Intel and AT&T/SVR4 syntaxes are supported, with the latter
being the default.  One difference is that AT&T syntax requires the '%'
prefix on register names while Intel syntax does not.  Another difference
is in the specification of relocatable expressions.  The Intel syntax
is @code{ha%expression} whereas the SVR4 syntax is @code{[expression]@@ha}
(and similarly for the "l" and "h" selectors).
@node Options-i860
@section i860 Command-line Options
@subsection SVR4 compatibility options 
@table @code
@item -V
Print assembler version.
@item -Qy
Ignored.
@item -Qn
Ignored.
@end table
@subsection Other options 
@table @code
@item -EL
Select little endian output (this is the default).
@item -EB
Select big endian output. Note that the i860 always reads instructions
as little endian data, so this option only effects data and not
instructions.
@item -mwarn-expand
Emit a warning message if any pseudo-instruction expansions occurred.
For example, a @code{or} instruction with an immediate larger than 16-bits
will be expanded into two instructions. This is a very undesirable feature to
rely on, so this flag can help detect any code where it happens. One
use of it, for instance, has been to find and eliminate any place
where @code{gcc} may emit these pseudo-instructions.
@item -mxp
Enable support for the i860XP instructions and control registers.  By default,
this option is disabled so that only the base instruction set (i.e., i860XR)
is supported.
@item -mintel-syntax
The i860 assembler defaults to AT&T/SVR4 syntax.  This option enables the
Intel syntax.
@end table

@node Directives-i860
@section i860 Machine Directives

@cindex machine directives, i860
@cindex i860 machine directives

@table @code
@cindex @code{dual} directive, i860
@item .dual
Enter dual instruction mode. While this directive is supported, the
preferred way to use dual instruction mode is to explicitly code
the dual bit with the @code{d.} prefix.
@end table

@table @code
@cindex @code{enddual} directive, i860
@item .enddual
Exit dual instruction mode. While this directive is supported, the
preferred way to use dual instruction mode is to explicitly code
the dual bit with the @code{d.} prefix.
@end table

@table @code
@cindex @code{atmp} directive, i860
@item .atmp
Change the temporary register used when expanding pseudo operations. The
default register is @code{r31}.
@end table

The @code{.dual}, @code{.enddual}, and @code{.atmp} directives are available only in the Intel syntax mode.

Both syntaxes allow for the standard @code{.align} directive.  However,
the Intel syntax additionally allows keywords for the alignment
parameter: "@code{.align type}", where `type' is one of @code{.short}, @code{.long},
@code{.quad}, @code{.single}, @code{.double} representing alignments of 2, 4,
16, 4, and 8, respectively.

@node Opcodes for i860
@section i860 Opcodes

@cindex opcodes, i860
@cindex i860 opcodes
All of the Intel i860XR and i860XP machine instructions are supported. Please see
either @emph{i860 Microprocessor Programmer's Reference Manual} or @emph{i860 Microprocessor Architecture} for more information.
@subsection Other instruction support (pseudo-instructions)
For compatibility with some other i860 assemblers, a number of
pseudo-instructions are supported. While these are supported, they are
a very undesirable feature that should be avoided -- in particular, when
they result in an expansion to multiple actual i860 instructions. Below
are the pseudo-instructions that result in expansions.
@itemize @bullet
@item Load large immediate into general register:

The pseudo-instruction @code{mov imm,%rn} (where the immediate does
not fit within a signed 16-bit field) will be expanded into:
@smallexample
orh large_imm@@h,%r0,%rn
or large_imm@@l,%rn,%rn
@end smallexample
@item Load/store with relocatable address expression:

For example, the pseudo-instruction @code{ld.b addr_exp(%rx),%rn} 
will be expanded into:
@smallexample
orh addr_exp@@ha,%rx,%r31
ld.l addr_exp@@l(%r31),%rn
@end smallexample

The analogous expansions apply to @code{ld.x, st.x, fld.x, pfld.x, fst.x}, and @code{pst.x} as well.
@item Signed large immediate with add/subtract:

If any of the arithmetic operations @code{adds, addu, subs, subu} are used
with an immediate larger than 16-bits (signed), then they will be expanded.
For instance, the pseudo-instruction @code{adds large_imm,%rx,%rn} expands to:
@smallexample 
orh large_imm@@h,%r0,%r31
or large_imm@@l,%r31,%r31
adds %r31,%rx,%rn
@end smallexample
@item Unsigned large immediate with logical operations:

Logical operations (@code{or, andnot, or, xor}) also result in expansions.
The pseudo-instruction @code{or large_imm,%rx,%rn} results in:
@smallexample
orh large_imm@@h,%rx,%r31
or large_imm@@l,%r31,%rn
@end smallexample

Similarly for the others, except for @code{and} which expands to:
@smallexample
andnot (-1 - large_imm)@@h,%rx,%r31
andnot (-1 - large_imm)@@l,%r31,%rn
@end smallexample
@end itemize