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From: "Maciej W. Rozycki" <macro@linux-mips.org>
To: Ralf Baechle <ralf@linux-mips.org>, Paul Burton <paul.burton@mips.com>
Cc: linux-mips@linux-mips.org, linux-kernel@vger.kernel.org
Subject: [PATCH 0/2] MIPS: memset: Fix `noreorder' issues
Date: Tue, 2 Oct 2018 12:50:00 +0100 (BST)	[thread overview]
Message-ID: <alpine.LFD.2.21.1810020209310.20762@eddie.linux-mips.org> (raw)

Hi,

 A recent change broke CPU_DADDI_WORKAROUNDS support in memset.S, due to a 
delay-slot instruction expanding to multiple hardware operations for the 
affected configurations.

 The underlying cause is the excessive use of the `noreorder' assembly 
mode, while it is only needed in couple of places where either there is a 
data dependency between a branch and its delay slot instruction, or there 
is a section switch involved that would prevent automatic delay slot 
scheduling.

 These changes address both problems and for clarity, not to mix multiple 
conceptually separate changes and to make backporting easier I made them a 
small patch series.  See individual change descriptions for details.

 This has been build-time and run-time verified with 32-bit and 64-bit 
DECstation configurations, build-time verified with big-endian and 
little-endian 64-bit SWARM configurations.  Build-time verification was 
made by running `objdump -d arch/mips/lib/memset.o' with a pristine and 
and a patched build to make sure there has been no change in machine code 
generation, except for the delay-slot multiple instruction with the 64-bit 
CPU_DADDI_WORKAROUNDS DECstation configuration.

 Please apply.

  Maciej

             reply	other threads:[~2018-10-02 11:50 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-10-02 11:50 Maciej W. Rozycki [this message]
2018-10-02 11:50 ` [PATCH 1/2] MIPS: memset: Fix CPU_DADDI_WORKAROUNDS `small_fixup' regression Maciej W. Rozycki
2018-10-02 11:50 ` [PATCH 2/2] MIPS: memset: Limit excessive `noreorder' assembly mode use Maciej W. Rozycki
2018-10-11 16:36 ` [PATCH 0/2] MIPS: memset: Fix `noreorder' issues Paul Burton

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