target/9633: i386 SSE intrinsics generate wrong code when spilling to stack

[felix-gcc@fefe.de]

>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: