Re: optimization/8878: miscompilation with -O and SSE

[Janis Johnson <janis187@us.ibm.com>]

The following reply was made to PR optimization/8878; it has been noted by GNATS.

From: Janis Johnson <janis187@us.ibm.com>
To: Volker Reichelt <reichelt@igpm.rwth-aachen.de>
Cc: janis187@us.ibm.com, gcc-gnats@gcc.gnu.org, gcc-bugs@gcc.gnu.org,
   kronoz@tiscali.it
Subject: Re: optimization/8878: miscompilation with -O and SSE
Date: Wed, 2 Apr 2003 11:44:27 -0800

 On Wed, Apr 02, 2003 at 09:17:49PM +0200, Volker Reichelt wrote:
 > Hi Janis,
 > 
 > PR 8878 got fixed on mainline in the last couple of days (somewhere
 > between 2003-03-29 and 2003-04-02).
 > Since the bug is in the category "wrong-code" it would be nice
 > if the patch could be backported to 3.3 (and maybe even 3.2) to
 > prevent silent miscompilations.
 > 
 > Could you please identify the patch that fixed the problem?
 > Maybe the following testcase is more convenient for the hunt,
 > since you can check the return value instead of the output:
 > 
 > ------------------------snip here----------------------------
 > typedef int v4sf __attribute__((mode(V4SF)));
 > 
 > int main(void)
 > {
 >     v4sf v = {1.0, 2.0, 3.0, 4.0};
 >     union { v4sf v; float f[4]; } u;
 > 
 >     u.v = __builtin_ia32_mulps(v,v);
 > 
 >     return u.f[0];
 > }
 > ------------------------snip here----------------------------
 > 
 > Just compile with "gcc -march=i686 -msse -O".
 
 I don't know much about x86 architectures and what's
 supposed to work where, but on my Pentium III this gets
 "Illegal instruction" when run, using a mainline compiler
 from sources updated yesterday.
 
 Janis