[PATCH] D128382: [LLD] Two tweaks to symbol ordering scheme

[YongKang Zhu via Phabricator via llvm-commits]

yozhu added a comment.

In D128382#3611207 <https://reviews.llvm.org/D128382#3611207>, @MaskRay wrote:

> In D128382#3611193 <https://reviews.llvm.org/D128382#3611193>, @yozhu wrote:
>
>> In D128382#3610276 <https://reviews.llvm.org/D128382#3610276>, @MaskRay wrote:
>>
>>> In D128382#3609648 <https://reviews.llvm.org/D128382#3609648>, @lanza wrote:
>>>
>>>> One interesting note Shoaib and I just discovered is that ~16.5% of the libraries in one of our major apps have `.text` sections starting on the first page of the dso. Placing hot sections at the front of the `.text` section would give us a slice of a "free page" that, with the current algorithm, would just be cold code that's less likely to be used. I imagine this isn't a substantial difference but it's probably slightly in favor of placing hot code first here.
>>>
>>> Thanks. This is fine, even if not that large. The patch should use `osec->flags & SHF_EXECINSTR` instead of `executableInputSections` for simplification. Then the complexity/benefit trade-off will look fine.
>>
>> I didn't check output section's attribute but instead check on each input section because:
>>
>> - It could be that the output section contains .text (RX) contributions as well as .rdata (R) contributions, like read-only data is merged into text section.
>
> This implies a linker script placing rodata into an executable output section.
> This is a corner case and the operation here does not matter. Just be simple.

Even if it is a rare or corner case, it is still a valid case.  Counting `executableInputSections` doesn't add many cycles.  Why not just cover all the possible cases?


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