[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, 8:21:50 PM, you wrote:
> 
> []
> 
>>>> 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?
> 
>   Well common Thumb intros usually have something like "Using Thumb
> can usually reduce code size 1.5 times, while reducing performance by
> 20% because of longer instruction sequences for some operations.".

Yeah, that's what you'd usually see. When I was attending a talk about DSPs[1] at SPS, the
speaker declared "[..] using thumb for better performance." which amused me and other
attendees :)

It's all about which kool-aid you drink.

regards,

Koen

[1] http://acivs.org/sps2006/AbstractList.php?type=regular#159
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