---------------------------------
cat >bug.c<<EOF
#include <stdlib.h>

typedef int di __attribute__ ((mode(DI)));

double x;
di mm;

double f ()
{
	return 1.0;
}

void f2 ()
{
	x = f ();
	mm = __builtin_ia32_pxor (mm, mm);
	
	/* clear MMX state after using MMX unit */
	__builtin_ia32_emms ();
}

int main ()
{
	f2 ();
	if (x != 1.0)
		abort ();
	return 0;
}
EOF
gcc -O2 -mmmx bug.c -o bug
./bug
---------------------------------

I get 'Aborted' with 3.3.4, 3.4.0, 3.5.0, and do not get it if I compile this
with -O1.

Below is an assembly code for f2 (), compiled with today's 3.4.0:
f2:
	pushl	%ebp	#
	movl	%esp, %ebp	#,
	call	f	#
	movq	mm, %mm0	# mm, mm
	fstpl	x	# x
	pxor	%mm0, %mm0	#, mm
	movq	%mm0, mm	# mm, mm
	emms
	leave
	ret

FPU insns should not be mixed with MMX ones, or they will fail.