Re: [Sbcl-devel] [PATCH] Branch relaxation for mips

[Christophe R. <cs...@ca...>]

Thiemo Seufer <th...@ne...> writes:

> Christophe Rhodes wrote:
>> Thiemo Seufer <th...@ne...> writes:
>> 
>> > the appended patch implements branch relaxation in the mips port
>> > for branches >18 bits. It also fixes the dependency declarations
>> > for some branch instructions.
>> 
>> Thank you; merged in sbcl-0.9.1.36.
>
> A small followup patch, whic uses "when" instead of "if".
>
> +	    (when (= opcode bcond-op)
> +		  (when (logand r2 #b10000)
> +			(progn (setf r2 (logand r2 #b01111))
> +			       (setf linked t))))

Ah, but... here the indentation is all wrong :-)

WHEN has the macro lambda list (test &body body), and the Lisp
community over many years has essentially standardized on indenting
body forms just two spaces from their parent form.  So a standard WHEN
expression should be formatted as
  (when (= opcode bcond-op)
    (do-something)
    (do-something else)
    (and so on))

If the test, for some reason, needed to be on its own line, then the
indentation would be
  (when
      (= opcode bcond-op)
    (do-something))
so that the test, which is not a body form, is visually distinguished.

This is a pretty general rule, by the way, so even things like
multiple-value-bind end up looking like
  (multiple-value-bind
        (foo bar)
      (truncate 19 3)
    (frob foo)
    (frob bar)
    (frob baz))
if all the subforms are split onto their own lines.

If you're using emacs, (setq lisp-indent-function
'common-lisp-indent-function) gets you a certain amount of the way
there, though that indent function doesn't do complex loop, or indeed
define-vop, terribly well.

Cheers,

Christophe