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Re: [PATCH-v4] [SPARC] Add a workaround for the LEON3FT store-store errata
- From: Daniel Cederman <cederman at gaisler dot com>
- To: Eric Botcazou <ebotcazou at adacore dot com>
- Cc: gcc-patches at gcc dot gnu dot org, sebastian dot huber at embedded-brains dot de, davem at davemloft dot net, daniel at gaisler dot com
- Date: Tue, 11 Jul 2017 10:13:16 +0200
- Subject: Re: [PATCH-v4] [SPARC] Add a workaround for the LEON3FT store-store errata
- Authentication-results: sourceware.org; auth=none
- References: <20170707114255.14273-1-cederman@gaisler.com> <1822257.v460k5UjUX@polaris>
On 2017-07-11 09:21, Eric Botcazou wrote:
Applied without the undocumented tweaks to the divdf3_fix and sqrtdf2_fix
patterns. Why are 2 nops necessary here? The stored value doesn't matter.
And the length attribute should be adjusted if nops are added to the pattern.
The first nop was added to prevent sequence A from appearing (store ->
fdivd -> std). But as you say, it is not needed as we do not read the
value written by the std. The second nop was added to prevent sequence B
(std -> store) and this one seems necessary as the value written by the
store might be used later. OK to submit a new patch with only the second
nop and a correct length attribute?
--
Daniel Cederman
Cobham Gaisler