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SubjectRe: [PATCH 0/2] MIPS: memset: Fix `noreorder' issues
Date
Hi Maciej,

On Tue, Oct 02, 2018 at 12:50:00PM +0100, Maciej W. Rozycki wrote:
> 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.

Thanks - I applied patch 1 to mips-fixes & it's already been merged to
master.

Patch 2 applied to mips-next for 4.20.

Paul

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