didn't provide a constant for one of them (non-IEEE denormal trap),
in an attempt to not support it probably, it's not we are left with
the lower 5 bits.
o Properly mask the passed or returned fp_except_t. Not doing so
causes instant core dumps by trying to write an invalid value to
ar.fpsr. Now that we're masking, stop using exclusive-or to invert
bits.
This fixes the illegal instruction fault encountered when building
mozilla.
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