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From: felix-gcc@fefe.de
To: gcc-gnats@gcc.gnu.org
Subject: target/9633: i386 SSE intrinsics generate wrong code when spilling to stack
Date: Sun, 09 Feb 2003 03:16:00 -0000 [thread overview]
Message-ID: <20030209030913.GA25258@codeblau.de> (raw)
>Number: 9633
>Category: target
>Synopsis: i386 SSE intrinsics generate wrong code when spilling xmm registers to stack
>Confidential: no
>Severity: critical
>Priority: medium
>Responsible: unassigned
>State: open
>Class: wrong-code
>Submitter-Id: net
>Arrival-Date: Sun Feb 09 03:16:00 UTC 2003
>Closed-Date:
>Last-Modified:
>Originator: Fefe
>Release: 3.4 20030129 (experimental)
>Organization:
>Environment:
System: Linux hellhound 2.4.20-wolk4.0s-pre7 #2 Wed Jan 22 13:14:55 CET 2003 i686 AMD Athlon(tm) XP 2000+ AuthenticAMD GNU/Linux
Architecture: i686
host: i686-pc-linux-gnu
build: i686-pc-linux-gnu
target: i686-pc-linux-gnu
configured with: ./configure --program-transform-name=s/^/e/ --prefix=/opt/gcc --with-local-prefix=/usr/local --disable-nls : (reconfigured) ./configure --program-transform-name=s/^/e/ --prefix=/opt/gcc --with-local-prefix=/usr/local --disable-nls --enable-__cxa_atexit
>Description:
When compiling SSE code without optimization (or when using it
in a way that makes gcc think it needs to spill xmm registers to
the stack), gcc will not make sure the stack is 16-byte aligned.
That causes the SSE store instruction to generate a segmentation
fault. This behavior is in 3.1.1 (earliest I have) up to the
current 3.4 CVS.
>How-To-Repeat:
$ cat ssebug.c
#include <xmmintrin.h>
main() {
static float scale=32768.f;
__m128 Scale=_mm_load1_ps(&scale);
}
$ gcc -o ssebug ssebug.c -msse
$ ./ssebug
[segfault]
>Fix:
align the stack variables.
Since spilling to the stack in most cases negates the
performance gain the programmer hopes for with SSE, I also
suggest a compiler warning in this case.
>Release-Note:
>Audit-Trail:
>Unformatted:
reply other threads:[~2003-02-09 3:16 UTC|newest]
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