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Re: [PATCH 1/2] target/ppc: Fixed call to deferred exception
From: |
Lucas Mateus Martins Araujo e Castro |
Subject: |
Re: [PATCH 1/2] target/ppc: Fixed call to deferred exception |
Date: |
Wed, 10 Nov 2021 14:29:01 -0300 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.13.0 |
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)