Re: [Sbcl-devel] [PATCH] NetBSD/ppc (not fully working yet)

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

Richard M Kreuter <kr...@pr...> writes:

> (1) I can't get %alien-funcall to work properly for a C function that
>     takes a 64-bit argument and returns a 64-bit value.  Here's what
>     happens when I tried compiling unix-lseek (off_t is a 64-bit
>     quantity on NetBSD):

I think I know what's going on.  See below, for interspersed comments.

> --- sbcl/src/code/unix.lisp	2005-10-12 11:12:17.000000000 -0400
> +++ sbcl-netbsd-ppc/src/code/unix.lisp	2005-12-10 20:49:56.000000000 -0500
> @@ -237,9 +237,17 @@ SYSCALL-FORM. Repeat evaluation of SYSCA
>    "
>    (declare (type unix-fd fd)
>             (type (integer 0 2) whence))
> -  (let ((result (alien-funcall (extern-alien "lseek" (function off-t int off-t int))
> +  (let ((result (alien-funcall (extern-alien "lseek"
> +					     ;; I (RMK) can't make
> +					     ;; %alien-funcall like
> +					     ;; this alien function on
> +					     ;; netbsd/ppc
> +					     #!-(and netbsd ppc)
> +					     (function off-t int off-t int)
> +			                     #!+(and netbsd ppc)
> +					     (function int int off-t int))
>                   fd offset whence)))
> -    (if (minusp result )
> +    (if (minusp result)
>          (values nil (get-errno))
>        (values result 0))))

I think here you've possibly been tripped up by the notation: I had to
read this a number of times before I realised what was happening.

You've patched the type of lseek from (function off-t int off-t int)
to (function int int off-t int); at first, I thought that this was to
avoid your "hackaround" from being triggered, but in fact it's nothing
of the kind.  The first INT there is the return value, not an
argument; you've changed the return value size, which explains the
error message you're getting in warm init.  So...

> diff -purN -xCVS -x'*.d' -xcustomize-target-features.lisp sbcl/src/compiler/ppc/c-call.lisp sbcl-netbsd-ppc/src/compiler/ppc/c-call.lisp
> --- sbcl/src/compiler/ppc/c-call.lisp	2005-11-06 08:25:50.000000000 -0500
> +++ sbcl-netbsd-ppc/src/compiler/ppc/c-call.lisp	2005-12-10 19:12:35.000000000 -0500
> @@ -238,7 +238,7 @@
>                 (alien-fun-type-result-type type)
>                 #!+darwin (make-result-state))))))
>  
> -#!+darwin
> +#!+(or darwin netbsd)
>  (deftransform %alien-funcall ((function type &rest args))
>    (aver (sb!c::constant-lvar-p type))
>    (let* ((type (sb!c::lvar-value type))
> @@ -262,6 +262,15 @@
>                              ;; 64-bit long long types are stored in
>                              ;; consecutive locations, most significant word
>                              ;; first (big-endian).
> +			    ;; On NetBSD, 64-bit quantities seem to
> +			    ;; need start in registers NLx, where x is
> +			    ;; even. -- RMK 20051129
> +			    #!+netbsd
> +			    (when (oddp (length (new-args)))
> +			      (new-args 0)
> +			      (new-arg-types
> +			       (parse-alien-type '(unsigned 32)
> +						 (sb!kernel:make-null-lexenv))))
>                              (new-args `(ash ,arg -32))
>                              (new-args `(logand ,arg #xffffffff))
>                              (if (alien-integer-type-signed type)

... this hackaround for 64-bit arguments is probably correct; however,
you need to do a little bit more work: you also need to teach the
compiler how to deal with two integer return values.  This is done in
!DEF-VM-SUPPORT-ROUTINE MAKE-CALL-OUT-TNS and in
DEFINE-ALIEN-TYPE-METHOD INTEGER :RESULT-TN, both in c-call.lisp just
above the %alien-funcall deftransform.  I suspect that basically
copying the #!+darwin clauses will make it work.

Cheers,

Christophe