[RFC/PATCH 0/3] ARM: Use udiv/sdiv for __aeabi_{u}idiv library functions

Måns Rullgård
2015-11-24T12:10:02Z

Russell King - ARM Linux <linux@arm.linux.org.uk> writes:

> On Tue, Nov 24, 2015 at 11:38:53AM +0100, Arnd Bergmann wrote:
>> I suggested using -mcpu=cortex-a15 because there are old gcc versions
>> that don't know about -march=armv7ve or -march=armv7-a+idiv yet, but
>> that do understand -mcpu=cortex-a15.
>
> That's not all. The bigger problem is that there are toolchains out
> there which accept these options, but do _not_ support IDIV in either
> ARM or Thumb mode. I'm afraid that makes it impossible to add this
> feature to the mainline kernel in this form: we need to run a test
> build to check that -march=armv7ve or what-not really does work
> through both GCC and GAS.

If the compiler accepts the option but doesn't actually emit any div
instructions, is there any real harm?

--
M?ns Rullg?rd
mans at mansr.com