[gentoo-embedded] creating a new aarch64 keyword

[gentoo-embedded] creating a new aarch64 keyword

[Mike Frysinger]

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originally i was going to reuse ARCH=arm for aarch64 (and that's what the code 
in the tree is doing now).  however, after playing with things and debating it 
in my head, i think we should create a new ARCH=aarch64.

reasons:
 - aarch64 is not a simple extension over arm at the ISA level like x86_64 is 
over i686.  it's a new ISA.
 - hand written assembly language cannot be shared at all -- with x86_64, you 
could sometimes write code that the assembler would automatically turn into 
the right output (64bit/x32/32bit).
 - the aarch64 gcc port itself does not support arm -- you need a complete 
second toolchain
 - the way the hardware is being designed, it is possible to have a CPU that 
only supports aarch64 (no arm at all)

it does mean we'll have to re-seed ebuilds with KEYWORDS=aarch64, but that's 
just how it goes.
-mike

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Re: [gentoo-embedded] creating a new aarch64 keyword

[Jason Cooper]

Mike,

On Thu, Jan 09, 2014 at 12:03:52PM -0500, Mike Frysinger wrote:
> originally i was going to reuse ARCH=arm for aarch64 (and that's what the code 
> in the tree is doing now).  however, after playing with things and debating it 
> in my head, i think we should create a new ARCH=aarch64.
> 
> reasons:
>  - aarch64 is not a simple extension over arm at the ISA level like x86_64 is 
> over i686.  it's a new ISA.
>  - hand written assembly language cannot be shared at all -- with x86_64, you 
> could sometimes write code that the assembler would automatically turn into 
> the right output (64bit/x32/32bit).
>  - the aarch64 gcc port itself does not support arm -- you need a complete 
> second toolchain
>  - the way the hardware is being designed, it is possible to have a CPU that 
> only supports aarch64 (no arm at all)

Agreed.  What platform (if any) are you developing/testing on?

thx,

Jason.

Re: [gentoo-embedded] creating a new aarch64 keyword

[Mike Frysinger]

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On Thursday 09 January 2014 12:03:52 Mike Frysinger wrote:
> originally i was going to reuse ARCH=arm for aarch64 (and that's what the
> code in the tree is doing now).  however, after playing with things and
> debating it in my head, i think we should create a new ARCH=aarch64.
> 
> reasons:
>  - aarch64 is not a simple extension over arm at the ISA level like x86_64
> is over i686.  it's a new ISA.
>  - hand written assembly language cannot be shared at all -- with x86_64,
> you could sometimes write code that the assembler would automatically turn
> into the right output (64bit/x32/32bit).
>  - the aarch64 gcc port itself does not support arm -- you need a complete
> second toolchain
>  - the way the hardware is being designed, it is possible to have a CPU
> that only supports aarch64 (no arm at all)
> 
> it does mean we'll have to re-seed ebuilds with KEYWORDS=aarch64, but
> that's just how it goes.

i ended up renaming to KEYWORDS=arm64:
	- it's the name Debian has picked
	- it's the name the kernel uses
	- the CrOS guys have a preference for that over aarch64
	- when you sort KEYWORDS, these will end up next to each other

since it really doesn't matter to us (it's bikeshedding either way), i just 
went with it
-mike

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Re: [gentoo-embedded] creating a new aarch64 keyword

[Mike Frysinger]

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On Friday 10 January 2014 17:02:17 Jason Cooper wrote:
> Agreed.  What platform (if any) are you developing/testing on?

personally i am just cross-compiling / using the reference sim right now
-mike

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