void
os_restore_fp_control(os_context_t *context)
{
- unsigned long control;
+ /* KLUDGE: mtfsf has to be run against a float register, so we
+ * construct the float we need to use as an integer, then cast
+ * a pointer to its storage to a double and load that. For
+ * this to work, control must be the same width as a double,
+ * 64 bits. And why aren't we using a union here, anyway? */
+ unsigned long long control;
double d;
+ /* FIXME: We are only preserving enabled traps and rounding
+ * mode here. Do we also want to preserve "fast mode"? */
control = os_context_fp_control(context) &
- /* FIXME: Should we preserve the user's requested rounding mode?
-
- Note that doing
-
- ~(FLOAT_STICKY_BITS_MASK | FLOAT_EXCEPTIONS_BYTE_MASK)
-
- here leads to infinite SIGFPE for invalid operations, as
- there are bits in the control register that need to be
- cleared that are let through by that mask. -- CSR, 2002-07-16 */
-
- FLOAT_TRAPS_BYTE_MASK;
+ (FLOAT_TRAPS_BYTE_MASK | FLOAT_ROUNDING_MODE_MASK);
d = *((double *) &control);
- /* Hmp. Apparently the following doesn't work either:
-
asm volatile ("mtfsf 0xff,%0" : : "f" (d));
-
- causing segfaults at the first GC.
- */
}
void