optimization/3480: gcc-3.0, bad code generated with -O3 -fomit-frame-pointer on intel x86

[Juergen Keil]

> Synopsis: gcc-3.0, bad code generated with -O3 -fomit-frame-pointer on intel 
x86
> 
> State-Changed-From-To: open->feedback
> State-Changed-By: rodrigc
> State-Changed-When: Sat Dec  1 22:49:12 2001
> State-Changed-Why:
>     I think this has been fixed by:
>     http://gcc.gnu.org/ml/gcc-patches/2001-11/msg00698.html
>     
>     Can you try a gcc 3.0.3 snapshot and verify this?
> 
> 
http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&pr=3480&database=g
cc


Yes, the problem seems to be fixed.


I've downloaded and installed snapshot gcc-20011126 and the code
generated for the problematic function 'acmStreamOpen' looks much better
now:

        .type   acmStreamOpen,@function
acmStreamOpen:
        pushl   %ebp
        pushl   %edi
        pushl   %esi
        pushl   %ebx
        subl    $16, %esp
        movl    44(%esp), %esi  <-- third parameter is now accessed via %esp 
with correct offset
        movzwl  16(%esi), %ecx
        movl    48(%esp), %ebx



In the released versions of gcc-3.0.x, the following buggy code is generated
(from my bug report)

	.globl acmStreamOpen
	.type acmStreamOpen,@function
	acmStreamOpen:
	pushl %ebp
	pushl %edi
	pushl %esi
	pushl %ebx
	subl $96, %esp
	movl 12(%ebp), %esi <--- accesses pwfxSrc as offset(%ebp), no
			    <--- valid %ebp setup yet!
	movzwl 16(%esi), %edx
	movl 16(%ebp), %ebx


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Jürgen Keil          		jk@tools.de
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