[PATCH, v3] ARM: Integrate Cortex-A15 optimized memcpy using NEON/VFP.

[Schwarz, Konrad]

> -----Original Message-----
> From: newlib-owner@sourceware.org [mailto:newlib-owner@sourceware.org]
> On Behalf Of Will Newton
> Sent: Thursday, April 11, 2013 10:14 PM
> To: Ramana Radhakrishnan
> Cc: newlib@sourceware.org
> Subject: Re: [PATCH, v3] ARM: Integrate Cortex-A15 optimized memcpy
> using NEON/VFP.

My apologies if this has all been answered before, but the floating-point
units I am familiar with usually allow lazy context switching.
A common operating system optimization is give threads a floating point
context only after they actually start executing floating point operations.
(The initial floating point instruction causes a trap; the OS can
initializes the thread's floating point context before restarting
the instruction.)
Threads start off as integer (register) context only.

Won't an implementation of a nominally non-floating point function
such as memcpy break this optimization, and perhaps be harmful from
a system standpoint?

In bare-metal systems, the OS/Executive/whatever may not even have
have floating point support and would be in for a rude surprise
when they call memcpy().

Konrad Schwarz