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Update documentation

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* doc/body.texi: Correct wrong/outdated information for
	hton*, pusharg* and ret*, and add missing documentation
	for rsb*, qmul*, qdvi* and putarg*.
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pcpa 2015-01-17 13:09:08 -02:00
parent 361caf2854
commit 3695a2e99c
2 changed files with 51 additions and 10 deletions
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6
ChangeLog
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@ -1,3 +1,9 @@
2015-01-17 Paulo Andrade <pcpa@gnu.org>
* doc/body.texi: Correct wrong/outdated information for
hton*, pusharg* and ret*, and add missing documentation
for rsb*, qmul*, qdvi* and putarg*.
2015-01-15 Paulo Andrade <pcpa@gnu.org>
* configure.ac, lib/jit_disasm.c: Rewrite workaround

55
doc/body.texi
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@ -224,6 +224,8 @@ subxr O1 = O2 - (O3 + carry)
subxi O1 = O2 - (O3 + carry)
subcr O1 = O2 - O3, set carry
subci O1 = O2 - O3, set carry
rsbr _f _d O1 = O3 - O1
rsbi _f _d O1 = O3 - O1
mulr _f _d O1 = O2 * O3
muli _f _d O1 = O2 * O3
divr _u _f _d O1 = O2 / O3
@ -242,6 +244,27 @@ rshr _u O1 = O2 >> O3@footnote{The sign bit is propagated unless us
rshi _u O1 = O2 >> O3@footnote{The sign bit is propagated unless using the @code{_u} modifier.}
@end example
@item Four operand binary ALU operations
These accept two result registers, and two operands; the last one can
be an immediate. The first two arguments cannot be the same register.
@code{qmul} stores the low word of the result in @code{O1} and the
high word in @code{O2}. For unsigned multiplication, @code{O2} zero
means there was no overflow. For signed multiplication, no overflow
check is based on sign, and can be detected if @code{O2} is zero or
minus one.
@code{qdiv} stores the quotient in @code{O1} and the remainder in
@code{O2}. It can be used as quick way to check if a division is
exact, in which case the remainder is zero.
@example
qmulr _u O1 O2 = O3 * O4
qmuli _u O1 O2 = O3 * O4
qdivr _u O1 O2 = O3 / O4
qdivi _u O1 O2 = O3 / O4
@end example
@item Unary ALU operations
These accept two operands, both of which must be registers.
@example
@ -249,7 +272,7 @@ negr _f _d O1 = -O2
comr O1 = ~O2
@end example
There unary ALU operations are only defined for float operands.
These unary ALU operations are only defined for float operands.
@example
absr _f _d O1 = fabs(O2)
sqrtr O1 = sqrt(O2)
@ -335,9 +358,10 @@ two instructions actually perform the same task, yet they are
assigned to two mnemonics for the sake of convenience and
completeness. As usual, the first operand is the destination and
the second is the source.
The @code{_ul} variant is only available in 64-bit architectures.
@example
htonr @r{Host-to-network (big endian) order}
ntohr @r{Network-to-host order }
htonr _us _ui _ul @r{Host-to-network (big endian) order}
ntohr _us _ui _ul @r{Network-to-host order }
@end example
@item Load operations
@ -375,13 +399,15 @@ that uses the appropriate wordsize call.
These are:
@example
prepare (not specified)
pushargr _c _uc _s _us _i _ui _l _f _d
pushargi _c _uc _s _us _i _ui _l _f _d
pushargr _f _d
pushargi _f _d
arg _c _uc _s _us _i _ui _l _f _d
getarg _c _uc _s _us _i _ui _l _f _d
putargr _f _d
putargi _f _d
ret (not specified)
retr _c _uc _s _us _i _ui _l _f _d
reti _c _uc _s _us _i _ui _l _f _d
retr _f _d
reti _f _d
retval _c _uc _s _us _i _ui _l _f _d
epilog (not specified)
@end example
@ -398,11 +424,11 @@ the @code{pushargr} or @code{pushargi} to push the arguments @strong{in
left to right order}; and use @code{finish} or @code{call} (explained below)
to perform the actual call.
@code{arg} and @code{getarg} are used by the callee.
@code{arg}, @code{getarg} and @code{putarg} are used by the callee.
@code{arg} is different from other instruction in that it does not
actually generate any code: instead, it is a function which returns
a value to be passed to @code{getarg}.@footnote{``Return a
value'' means that @lightning{} code that compile these
a value to be passed to @code{getarg} or @code{putarg}. @footnote{``Return
a value'' means that @lightning{} code that compile these
instructions return a value when expanded.} You should call
@code{arg} as soon as possible, before any function call or, more
easily, right after the @code{prolog} instructions
@ -417,6 +443,15 @@ that generates other code, so they will be treated more
specifically in @ref{GNU lightning examples, , Generating code at
run-time}.
@code{putarg} is a mix of @code{getarg} and @code{pusharg} in that
it accepts as first argument a register or immediate, and as
second argument a value returned by @code{arg}. It allows changing,
or restoring an argument to the current function, and is a
construct required to implement tail call optimization. Note that
arguments in registers are very cheap, but will be overwritten
at any moment, including on some operations, for example division,
that on several ports is implemented as a function call.
Finally, the @code{retval} instruction fetches the return value of a
called function in a register. The @code{retval} instruction takes a
register argument and copies the return value of the previously called