From: Richard Henderson <richard.henderson@linaro.org>
To: Qi Hu <huqi@loongson.cn>, Song Gao <gaosong@loongson.cn>,
Xiaojuan Yang <yangxiaojuan@loongson.cn>
Cc: qemu-devel@nongnu.org, Feiyang Chen <chenfeiyang@loongson.cn>
Subject: Re: [PATCH] target/loongarch: Fix "movfcsr2gr" gets wrong value
Date: Sat, 6 Aug 2022 09:15:34 -0700 [thread overview]
Message-ID: <26f5be99-e9be-df9d-be50-1a2f2cd64986@linaro.org> (raw)
In-Reply-To: <20220806133426.542314-1-huqi@loongson.cn>
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~
next prev parent reply other threads:[~2022-08-06 16:18 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-08-06 13:34 [PATCH] target/loongarch: Fix "movfcsr2gr" gets wrong value Qi Hu
2022-08-06 16:15 ` Richard Henderson [this message]
2022-08-07 3:22 ` huqi
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