Re: [PATCH] target/loongarch: Fix "movfcsr2gr" gets wrong value

[Richard Henderson]

On 8/6/22 06:34, Qi Hu wrote:
> In follow sequence:
>    movgr2fcsr $r0,$r0
>    movgr2fr.d $f0,$r0
>    fdiv.d     $f0,$f0,$f0
>    movfcsr2gr $r12,$r0
>
> The value of $r12 is "0x00000000", but it should be "0x10100000"(V flag).
>
> These fp helpers are definded with wrong flag "TCG_CALL_NO_WG" (but the
> helpers write the globle "fcsr"). This causes the "fdiv" helper updates
> the "fcsr" into mem, but "movfcsr2gr" does not load it from mem.
>
> Reported-by: Feiyang Chen<chenfeiyang@loongson.cn>
> Signed-off-by: Qi Hu<huqi@loongson.cn>
> ---
>   target/loongarch/helper.h | 64 +++++++++++++++++++--------------------
>   1 file changed, 32 insertions(+), 32 deletions(-)

That's one solution, though it may perform less well.

The other is to remove cpu_fcsr0, and instead access that value with explicit loads and 
stores in the two (!) instructions that use that tcg temporary.


r~