On 10/11/2021 03:56, Cédric Le Goater wrote:
On 11/9/21 17:37, Daniel Henrique Barboza wrote:
On 10/20/21 09:57, Lucas Mateus Castro (alqotel) wrote:
From: "Lucas Mateus Castro (alqotel)" <lucas.castro@eldorado.org.br>
mtfsf, mtfsfi and mtfsb1 instructions call helper_float_check_status
after updating the value of FPSCR, but helper_float_check_status
checks fp_status and fp_status isn't updated based on FPSCR and
since the value of fp_status is reset earlier in the instruction,
it's always 0.
Because of this helper_float_check_status would change the FI bit to 0
as this bit checks if the last operation was inexact and
float_flag_inexact is always 0.
These instructions also don't throw exceptions correctly since
helper_float_check_status throw exceptions based on fp_status.
This commit created a new helper, helper_fpscr_check_status that checks
FPSCR value instead of fp_status and checks for a larger variety of
exceptions than do_float_check_status.
The hardware used to compare QEMU's behavior to, was a Power9.
Do you have a test case for this ? If so, are you collecting them
on some repo ?
Thanks,
C.
Just created a test, currently on the branch
https://github.com/PPC64/qemu/tree/alqotel_bug_mtfsf commit
c8a852bcdf7bdc239711679f00af2450c51d57c6
This test if FI is being set correctly and if the deferred exception is being
called correctly (by enabling VE and VXSOFT bits)