Re: [Sbcl-devel] Re: [Sbcl-commits] CVS: sbcl/src/compiler srctran.lisp,1.139,1.140

[Nathan F. <fr...@cs...>]

On Thu, May 18, 2006 at 01:02:49PM +0200, G=E1bor Melis wrote:
> There is a similar patch (at the end of this mail:=20
> http://article.gmane.org/gmane.lisp.steel-bank.devel/6045 ) that I=20
> haven't committed because it produces slightly worse code in some cases=
=20
> (at least on the x86, also in the mail). And it was a slight net loss=20
> on cl-bench.

Interesting, thanks for pointing this out.  I understand very little of
that email thread because the mechanics of typing in IR1 are quite
opaque to me. :)

I did try your example:

(defun xxx (x)
  (if (eq :something x)
      x ; modified as per Alexey's email
      0))

on something that roughly corresponds to CVS HEAD and noticed that
:SOMETHING was being loaded twice:

; 116065CD:       39056C656011     CMP [#x1160656C], EAX      ; :SOMETHIN=
G
                                                              ; no-arg-pa=
rsing entry point
;       D3:       7510             JNE L1
;       D5:       8B156C656011     MOV EDX, [#x1160656C]      ; :SOMETHIN=
G
;       DB: L0:   8D65F8           LEA ESP, [EBP-8]
;       DE:       F8               CLC
;       DF:       8B6DFC           MOV EBP, [EBP-4]
;       E2:       C20400           RET 4
;       E5: L1:   31D2             XOR EDX, EDX
;       E7:       EBF2             JMP L0

Curious, I tried the same thing on 0.9.10.41:

; 121E8395:       390534831E12     CMP [#x121E8334], EAX      ; :SOMETHIN=
G
                                                              ; no-arg-pa=
rsing entry point
;       9B:       750C             JNE L1
;       9D:       8BD0             MOV EDX, EAX
;       9F: L0:   8D65F8           LEA ESP, [EBP-8]
;       A2:       F8               CLC
;       A3:       8B6DFC           MOV EBP, [EBP-4]
;       A6:       C20400           RET 4
;       A9: L1:   31D2             XOR EDX, EDX
;       AB:       EBF2             JMP L0

And to see whether or not my changes caused this, 0.9.11.5:

; 115C4EED:       39058C4E5C11     CMP [#x115C4E8C], EAX      ; :SOMETHIN=
G
                                                              ; no-arg-pa=
rsing entry point
;      EF3:       740C             JEQ L1
;      EF5:       31D2             XOR EDX, EDX
;      EF7: L0:   8D65F8           LEA ESP, [EBP-8]
;      EFA:       F8               CLC
;      EFB:       8B6DFC           MOV EBP, [EBP-4]
;      EFE:       C20400           RET 4
;      F01: L1:   8B158C4E5C11     MOV EDX, [#x115C4E8C]      ; :SOMETHIN=
G
;      F07:       EBEE             JMP L0

FWIW, interesting.
--=20
Nathan | From Man's effeminate slackness it begins.  --Paradise Lost

The last good thing written in C was Franz Schubert's Symphony Number 9.
                                               --Erwin Dieterich