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Re: [Minios-devel] [PATCH v3 21/43] arm64: define the CALLEE_SAVED_REGISTERS





On 25/04/2018 18:33, Julien Grall wrote:
Hi,

Hi,


On 16/04/18 07:32, Huang Shijie wrote:
In the arm64, the callee-saved registers are x19 ~ x29.

s/In the/On/.

I think it would be good to mention where that convention comes from as this is not very obvious for non-arm expert :). This convention is from AAPCS64 [1].

Also, you want to explain why x19-x29. At first this is not obvious because the table call x29 "fp" and x19-x28 "callee-saved registers". It took me a bit to find in the spec the line saying "A subroutine invocation must preserve the contents of the registers r19-r29 and SP."

Cheers,

--
Julien Grall

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