Re: optimization/8049: SSE unaligned vector stores crash with -O0

[Tim Prince <tprince@computer.org>]

The following reply was made to PR optimization/8049; it has been noted by GNATS.

From: Tim Prince <tprince@computer.org>
To: iano@cco.caltech.edu, gcc-gnats@gcc.gnu.org
Cc:  
Subject: Re: optimization/8049: SSE unaligned vector stores crash with -O0
Date: Wed, 25 Sep 2002 20:13:05 -0700

 On Wednesday 25 September 2002 15:58, iano@cco.caltech.edu wrote:
 > >Number:         8049
 > >Category:       optimization
 > >Synopsis:       SSE unaligned vector stores crash with -O0
 > >Confidential:   no
 > >Severity:       critical
 > >Priority:       medium
 > >Responsible:    unassigned
 > >State:          open
 > >Class:          sw-bug
 > >Submitter-Id:   net
 > >Arrival-Date:   Wed Sep 25 16:06:00 PDT 2002
 > >Closed-Date:
 > >Last-Modified:
 > >Originator:     Ian Ollmann
 > >Release:        gcc 3.3 20020925 (experimental)
 > >Organization:
 > >Environment:
 >
 > Red Hat Linux 7.3 (P4/2530)
 >
 > >Description:
 >
 > I have encountered several cases at optimization level zero (-O0) wherein
 > the app seg faults on a movaps instruction just prior to calling
 > _mm_store_ps().
 >
 > gcc -O0 -msse -g main.c
 >
 > main.c:
 > -------
 > #include <xmmintrin.h>
 > #include <stdlib.h>
 >
 > void MatrixMultiply( float A[16], float B[16], float C[16] );
 >
 > int main( void )
 > {
 >     float 	A[16] __attribute__ ((aligned (16) ) );
 >     float	B[16] __attribute__ ((aligned (16) ) );
 >     float	C[16] __attribute__ ((aligned (16) ) );
 >     int i;
 >
 I've seen several discussions indicating why gcc is unable to support these 
 alignments in main().  In a search of gcc info, I don't find this point 
 explained adequately.  Ideally, the compiler would diagnose this as an error. 
 Also, somewhere, the measures required to get alignments on Windows targets 
 should be documented.
 
 -- 
 Tim Prince