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Date: Wed, 28 Apr 2004 14:30:47 -0500
From: Brian Ford <ford AT vss DOT fsi DOT com>
Reply-To: cygwin AT cygwin DOT com
To: cygwin AT cygwin DOT com
cc: tbp <gcc AT ompf DOT org>
Subject: Re: g++ 3.4.0 cygwin, codegen SSE & alignement issues
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On Wed, 28 Apr 2004, Christopher Faylor wrote:

> On Wed, Apr 28, 2004 at 12:41:51PM -0500, Brian Ford wrote:
> This patch would only affect non-main threads.  It would not affect the
> main thread.  Wouldn't you need to do the same thing for the main thread?
> I don't understand why it would be different.

Something already does.  I didn't try and track down the what/why.

00401060 <_main>:
   401060:       55                      push   %ebp
   401061:       b8 10 00 00 00          mov    $0x10,%eax
   401066:       89 e5                   mov    %esp,%ebp
   401068:       83 ec 08                sub    $0x8,%esp
   40106b:       83 e4 f0                and    $0xfffffff0,%esp <-- SEE

This problem doesn't happen for the main thread.  I'll try to pin the who
down if you like.

> >2004-04-28  DJ Delorie  <dj AT redhat DOT com>
> >
> >        * init.cc (threadfunc_fe): Hack to make thread stacks always 16
> >	byte aligned.
> >
> >Index: init.cc
> >===================================================================
> >RCS file: /cvs/src/src/winsup/cygwin/init.cc,v
> >retrieving revision 1.32
> >diff -u -p -r1.32 init.cc
> >--- init.cc     22 Mar 2004 18:30:38 -0000      1.32
> >+++ init.cc     28 Apr 2004 17:38:03 -0000
> >@@ -27,6 +27,8 @@ HANDLE sync_startup;
> > static void WINAPI
> > threadfunc_fe (VOID *arg)
> > {
> >+  (void)__builtin_return_address(1);
> >+  asm volatile ("andl $-16,%%esp" ::: "%esp");
> >   _cygtls::call ((DWORD (*)  (void *, void *)) (((char **)
> >_tlsbase)[OLDFUNC_OFFSET]), arg);
> > }

-- 
Brian Ford
Senior Realtime Software Engineer
VITAL - Visual Simulation Systems
FlightSafety International
the best safety device in any aircraft is a well-trained pilot...

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