* aarch32 acquire/release vs mttcg
@ 2018-11-06 11:55 ` Peter Maydell
0 siblings, 0 replies; 4+ messages in thread
From: Peter Maydell @ 2018-11-06 11:55 UTC (permalink / raw)
To: QEMU Developers; +Cc: qemu-arm, Richard Henderson, Alex Bennée
Looking through code I noticed that in target/arm/translate.c there
is the following comment in the decode for the load-acquire/store-release
instructions:
/* Since the emulation does not have barriers,
the acquire/release semantics need no special
handling */
This is out of date now we have MTTCG, isn't it?
The equivalent code in translate-a64.c has some calls to tcg_gen_mb()
to emit barriers...presumably we need to fix the a32 code to do
the same.
(We haven't noticed this because I think in practice nobody
much is compiling Armv8-specific AArch32 code.)
thanks
-- PMM
^ permalink raw reply [flat|nested] 4+ messages in thread* [Qemu-devel] aarch32 acquire/release vs mttcg
@ 2018-11-06 11:55 ` Peter Maydell
0 siblings, 0 replies; 4+ messages in thread
From: Peter Maydell @ 2018-11-06 11:55 UTC (permalink / raw)
To: QEMU Developers; +Cc: qemu-arm, Richard Henderson, Alex Bennée
Looking through code I noticed that in target/arm/translate.c there
is the following comment in the decode for the load-acquire/store-release
instructions:
/* Since the emulation does not have barriers,
the acquire/release semantics need no special
handling */
This is out of date now we have MTTCG, isn't it?
The equivalent code in translate-a64.c has some calls to tcg_gen_mb()
to emit barriers...presumably we need to fix the a32 code to do
the same.
(We haven't noticed this because I think in practice nobody
much is compiling Armv8-specific AArch32 code.)
thanks
-- PMM
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: aarch32 acquire/release vs mttcg
2018-11-06 11:55 ` [Qemu-devel] " Peter Maydell
@ 2018-11-06 14:23 ` Alex Bennée
-1 siblings, 0 replies; 4+ messages in thread
From: Alex Bennée @ 2018-11-06 14:23 UTC (permalink / raw)
To: Peter Maydell; +Cc: QEMU Developers, qemu-arm, Richard Henderson
Peter Maydell <peter.maydell@linaro.org> writes:
> Looking through code I noticed that in target/arm/translate.c there
> is the following comment in the decode for the load-acquire/store-release
> instructions:
>
> /* Since the emulation does not have barriers,
> the acquire/release semantics need no special
> handling */
>
> This is out of date now we have MTTCG, isn't it?
Yes
> The equivalent code in translate-a64.c has some calls to tcg_gen_mb()
> to emit barriers...presumably we need to fix the a32 code to do
> the same.
Sounds right. Are they the same semantics as their bigger 64 bit
cousins?
>
> (We haven't noticed this because I think in practice nobody
> much is compiling Armv8-specific AArch32 code.)
>
> thanks
> -- PMM
--
Alex Bennée
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [Qemu-devel] aarch32 acquire/release vs mttcg
@ 2018-11-06 14:23 ` Alex Bennée
0 siblings, 0 replies; 4+ messages in thread
From: Alex Bennée @ 2018-11-06 14:23 UTC (permalink / raw)
To: Peter Maydell; +Cc: QEMU Developers, qemu-arm, Richard Henderson
Peter Maydell <peter.maydell@linaro.org> writes:
> Looking through code I noticed that in target/arm/translate.c there
> is the following comment in the decode for the load-acquire/store-release
> instructions:
>
> /* Since the emulation does not have barriers,
> the acquire/release semantics need no special
> handling */
>
> This is out of date now we have MTTCG, isn't it?
Yes
> The equivalent code in translate-a64.c has some calls to tcg_gen_mb()
> to emit barriers...presumably we need to fix the a32 code to do
> the same.
Sounds right. Are they the same semantics as their bigger 64 bit
cousins?
>
> (We haven't noticed this because I think in practice nobody
> much is compiling Armv8-specific AArch32 code.)
>
> thanks
> -- PMM
--
Alex Bennée
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2018-11-06 14:23 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz follow: Atom feed
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2018-11-06 11:55 aarch32 acquire/release vs mttcg Peter Maydell
2018-11-06 11:55 ` [Qemu-devel] " Peter Maydell
2018-11-06 14:23 ` Alex Bennée
2018-11-06 14:23 ` [Qemu-devel] " Alex Bennée
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