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Re: [RFC][AARCH64] TARGET_ATOMIC_ASSIGN_EXPAND_FENV hook
- From: Marcus Shawcroft <marcus dot shawcroft at gmail dot com>
- To: Kugan <kugan dot vivekanandarajah at linaro dot org>
- Cc: "gcc-patches at gcc dot gnu dot org" <gcc-patches at gcc dot gnu dot org>
- Date: Fri, 2 May 2014 11:15:44 +0100
- Subject: Re: [RFC][AARCH64] TARGET_ATOMIC_ASSIGN_EXPAND_FENV hook
- Authentication-results: sourceware.org; auth=none
- References: <535B9132 dot 40703 at linaro dot org> <535E3503 dot 3020203 at arm dot com> <535F1061 dot 90908 at linaro dot org> <CAFqB+Pz4iGG3rjdD14GvE-o7F2msdeM_G3ANFNf5NwPtdHtbag at mail dot gmail dot com>
On 2 May 2014 11:06, Marcus Shawcroft <marcus.shawcroft@gmail.com> wrote:
> Kugan, I've not looked at the respin in detail yet, but it has just
> occurred to me that the sequence used here to set FPCR is
> insufficient. The architecture reference manual requires that any
> write to FPCR must be syncrhronized by a context synchronization
> operation so we need to plant an ISB after the write. Both the write
> and ISB are likely to be expensive on some implementations so it would
> be good to ensure that both the write and the isb are scheduled
> independently. IIRC there si
Sorry, incomplete sentence. I had started to write that IIRC the same
issue did not apply to FPSCR in the ARM patch. I have doubled checked
and the FPSCR does not have the issue therefore the ARM patch is fine
in this respect.
/Marcus