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[Gcl-devel] Re: 2.7.0 nqthm compile times


From: Camm Maguire
Subject: [Gcl-devel] Re: 2.7.0 nqthm compile times
Date: 22 Jun 2007 17:41:25 -0400
User-agent: Gnus/5.09 (Gnus v5.9.0) Emacs/21.2

Greetings!

[ cc'ed to the maxima and axiom lists, as I would greatly appreciate
any user feedback on what they would like (that is practical) in the
forthcoming gcl release.  If this is unwelcome traffic, please let me
know.]

Robert Boyer <address@hidden> writes:

> Fantastic.  Thanks so much!
> 

The above is most appreciated, but I was hoping for a bit more of an
opinion as to where GCL should be heading in this direction, to wit:

Code calling compiled functions of known signature can be rendered
incorrect if the callee is subsequently compiled to produce a
different signature:

=============================================================================
COMPILER>(defun foo (x y z) (list x y z))

FOO

COMPILER>(compile 'foo)

;; Compiling /tmp/gazonk_13883_1.lsp.
;; End of Pass 1.  
;; End of Pass 2.  
;; OPTIMIZE levels: Safety=0 (No runtime error checking), Space=0, Speed=3, 
(Debug quality ignored)
;; Finished compiling /tmp/gazonk_13883_1.o.
;; Loading /tmp/gazonk_13883_1.o
 ;; start address -T 0xaa2f80 ;; Finished loading /tmp/gazonk_13883_1.o
#<compiled-function FOO>
NIL
NIL

COMPILER>(defun bar (x y z zz) (remove zz (foo x y z)))

BAR

COMPILER>(compile 'bar)

;; Compiling /tmp/gazonk_13883_1.lsp.
;; End of Pass 1.  
;; End of Pass 2.  
;; OPTIMIZE levels: Safety=0 (No runtime error checking), Space=0, Speed=3, 
(Debug quality ignored)
;; Finished compiling /tmp/gazonk_13883_1.o.
;; Loading /tmp/gazonk_13883_1.o
;; start address -T 0x87b2b0 ;; Finished loading /tmp/gazonk_13883_1.o
#<compiled-function BAR>
NIL
NIL

COMPILER>(bar 1 2 3 1)

(2 3)

COMPILER>(setq si::*disable-recompile* t)

T

COMPILER>(defun foo (x y z) (coerce (list x y z) 'vector))

FOO

COMPILER>(compile 'foo)

;; Compiling /tmp/gazonk_13883_1.lsp.
; (DEFUN FOO ...) is being compiled.
;; Warning: ret type mismatch in auto-proclamation (CONS T
                                                    (CONS T
                                                     (CONS T NULL)))(NIL) -> *

;; End of Pass 1.  
;; End of Pass 2.  
;; OPTIMIZE levels: Safety=0 (No runtime error checking), Space=0, Speed=3, 
(Debug quality ignored)
;; Finished compiling /tmp/gazonk_13883_1.o.
;; Loading /tmp/gazonk_13883_1.o
 ;; start address -T 0x87b540 ;; Finished loading /tmp/gazonk_13883_1.o
#<compiled-function FOO>
NIL
NIL

COMPILER>(bar 1 2 3 1)
Segmentation violation: c stack ok:signalling error
Error: ERROR "Caught fatal error [memory may be damaged]: Segmentation 
violation."
Fast links are on: do (si::use-fast-links nil) for debugging
Signalled by BAR.
ERROR "Caught fatal error [memory may be damaged]: Segmentation violation."

Broken at BAR.  Type :H for Help.
COMPILER>>:q

Top level.
COMPILER>(setq si::*disable-recompile* nil)

NIL

COMPILER>(si::do-recompile)
Pass1 signature discovery on 1 functions ...
Compiling and loading new source in #<output stream 
"/tmp/gazonk_13883_jvaAQ9.lsp">
;; Compiling /tmp/gazonk_13883_jvaAQ9.lsp.
;; End of Pass 1.  
;; End of Pass 2.  
;; OPTIMIZE levels: Safety=0 (No runtime error checking), Space=0, Speed=3, 
(Debug quality ignored)
;; Finished compiling /tmp/gazonk_13883_jvaAQ9.o.
;; Loading /tmp/gazonk_13883_jvaAQ9.o
 ;; start address -T 0x87ff40 ;; Finished loading /tmp/gazonk_13883_jvaAQ9.o
done
NIL

COMPILER>(bar 1 2 3 1)

#(2 3)

COMPILER>(defun foo (x y z) (list x y z))

FOO

COMPILER>(compile 'foo)

;; Compiling /tmp/gazonk_13883_1.lsp.
;; End of Pass 1.  
;; End of Pass 2.  
;; OPTIMIZE levels: Safety=0 (No runtime error checking), Space=0, Speed=3, 
(Debug quality ignored)
;; Finished compiling /tmp/gazonk_13883_1.o.
;; Loading /tmp/gazonk_13883_1.o
Pass1 signature discovery on 1 functions ...
Compiling and loading new source in #<output stream 
"/tmp/gazonk_13883_XL6AKh.lsp">
;; Compiling /tmp/gazonk_13883_XL6AKh.lsp.
;; End of Pass 1.  
;; End of Pass 2.  
;; OPTIMIZE levels: Safety=0 (No runtime error checking), Space=0, Speed=3, 
(Debug quality ignored)
;; Finished compiling /tmp/gazonk_13883_XL6AKh.o.
;; Loading /tmp/gazonk_13883_XL6AKh.o
 ;; start address -T 0x880a20 ;; Finished loading /tmp/gazonk_13883_XL6AKh.o
 ;; start address -T 0x887320 ;; Finished loading /tmp/gazonk_13883_1.o
#<compiled-function FOO>
NIL
NIL

COMPILER>(bar 1 2 3 1)

(2 3)

COMPILER>
=============================================================================

The existing philosophy is therefore not to let the load of the new
foo complete without executing the recompile.  This has the
disadvantage of compiling functions possibly multiple times, and
fragmenting the contiguous memory space.

'si::do-recompile has the following behavior at the moment:

        a) if called without an argument, as is done in every loaded
        .o file, will 1) do a fast pass1-only signature discovery run
        on the out of date functions, 2) will write the necessary
        functions to a temporary file, compile and then load it.  Each
        function passes through gcc once, but possibly multiple times
        only through pass1.  System is left in a safe state, but code
        can be recompiled multiple times on subsequent multiple loads.

        b) if called with a non-nil argument, will do the above, but
        write the new source to the filespec provided in the argument,
        which is compiled but not loaded.  The system is left in an
        unsafe state, and implicitly leaves to the user the job of
        integrating the freshly compiled source.

        c) if called with a nil argument, will do the pass1 signature
        discovery, and collect a list of original source files
        containing the recompiled functions.  These files are then
        probed for and recompiled if found.  The system is left in an
        unsafe state, and implicitly leaves to the user the job of
        integrating the freshly recompiled code.  (These files cannot
        be automatically reloaded, as they may contain other top-level
        forms which are only intended to be executed once.  Given
        this, the load was also skipped for the non-nil argument case
        in b) by way of symmetry.  A third recompile for automatic
        loading purposes (as in a)) is ommitted to save compile time.)

'with-compilation-unit is as follows:

(defmacro with-compilation-unit (opt &rest body)   
  (declare (optimize (safety 1)))
  (declare (ignore opt)) 
  `(progn
     (let ((*disable-recompile* t))
       ,@body)
     (do-recompile nil)))

So at present it leaves the system in an unsafe state to avoid a
second pass through gcc and load for every recompiled function.  If
there are only compile-files and no loads in the unit, no signature
conflict is detected and no recompilation is done.  Only loaded
functions within the unit trigger recompilation at unit end.  This is
somewhat counter to what one might expect from the ansi-doc
definition, given its emphasis on compile-file item deferral.

Here are some alternatives:

1) do another pass through gcc followed by a load when passing the nil
   argument (or a just a load when passing the non-nil argument) to
   leave the system in a safe state at the expense of more compile
   time.

2) Never automatically recompile at load, leaving the safety < 3 user
   to the whims of random segfaults, but provide a safety 3 which
   eliminates all branch elimination depending on known return
   signatures.

3) Defer auto recompiles to a re-entry of top-level, minimizing the
   window of unsafe code execution.

...

Thoughts most appreciated.  Please help me make this serve the needs
of the community.  For those new to this thread, this mechanism
obviates the need for ftype declaims.  A final question remains of
whether or not to actually use ftype declaims if provided.

Take care,

-- 
Camm Maguire                                            address@hidden
==========================================================================
"The earth is but one country, and mankind its citizens."  --  Baha'u'llah




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