The instructions mtfsf, mtfsfi and mtfsb1, when called, fail to set the FI
bit (bit 46 in the FPSCR) and can set to 1 the reserved bit 52 of the
FPSCR, as reported in https://gitlab.com/qemu-project/qemu/-/issues/266
(although the bug report is only for mtfsf, the bug applies to mtfsfi and
mtfsb1 as well).
These instructions also fail to throw an exception when the exception
and enabling bits are set, this can be tested by adding
'prctl(PR_SET_FPEXC, PR_FP_EXC_PRECISE);' before the __builtin_mtfsf
call in the test case of the bug report.
These patches aim to fix these issues.