[oe] [RFC] Enable tune-thumb.inc for all armv5t and armv6t machines

[Koen Kooi]

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Paul Sokolovsky schreef:
> Hello Koen,
> 
> Thursday, December 21, 2006, 7:24:54 PM, you wrote:
> 
>> Hi,
> 
>> Today I seperated the thumb bits from
>> conf/machine/include/ipx4xx.conf into
>> conf/machine/include/. I'd like to enable for all >=v5t machines, but I'm unsure about
>> using positive or negative logic.
> 
>   What about armv4t?

The codesourcery people are telling horror stories to everyone about armv4t, but I don't
believe them anymore after
http://www.openembedded.org/repo/org.openembedded.dev/packages/gcc/gcc-4.1.1/unbreak-armv4t.patch
'fixed' EABI on armv4t. I get the distinct feeling csl is trying to strongarm people into
using armv5 and armv6.

>  plus, thumb has known drawback of reduced performance.

I know the 'bx' insn causes a pipeline flush on xscales, any other drawbacks? And more
importantly, any numbers?


> In ideal case, thumb usage would be set per-package

Yes, that's where ARM_INSTRUCTION_SET comes in :), although enabling it is messier as
disabling it.
I wasn't impressed by the numbers[1], but samba lost 0.5MB, so that's a candidate

regards,

Koen

[1] Ångström already uses -Os, so the binaries are already pretty small
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