How to understand the comment of macro *compute_indices*?

How to understand the comment of macro *compute_indices*?

[carver]

Hello,

Macro *compute_indices* in arch/arm64/kernel/head.S have a comment
as shown below:
	mov     \istart, \ptrs
	mul     \istart, \istart, \count
	add     \iend, \iend, \istart   // iend += (count - 1) * ptrs

I am wondering whether this comment should be change to 
"iend += count * ptrs".

Or am I misunderstanding this code?

Thanks

-Lio

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Re: How to understand the comment of macro *compute_indices*?

[Valdis Klētnieks]

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On Tue, 14 Jul 2020 07:54:04 +0800, carver said:
> Hello,
>
> Macro *compute_indices* in arch/arm64/kernel/head.S have a comment
> as shown below:
> 	mov     \istart, \ptrs
> 	mul     \istart, \istart, \count
> 	add     \iend, \iend, \istart   // iend += (count - 1) * ptrs
>
> I am wondering whether this comment should be change to
> "iend += count * ptrs".

Examine the uses of the macro, and see where they expect the result
to be pointing if there is exactly one entry. (Hint - what's the address of
the first entry of a C array, and what's the next location after the array,
and how would the corresponding C code for iterating across the array
have as the termination condition?)

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