[PATCH] D45571: [ELF] - Speedup MergeInputSection::splitStrings

[George Rimar via Phabricator via llvm-commits]

grimar added a comment.

In https://reviews.llvm.org/D45571#1081681, @espindola wrote:

> The test results are interesting
>
> The geometric mean for seconds-elapsed improves by 0.5%. Scylla is just 0.3% faster.


Strange, because I am observing stable major boost. Restested today just in case.
Total CPU time, 3 runs, MSVS profiler, RelWithDebInfo configuration, linking `\lld-speed-test\scylla`.
Windows 8, i7-4970K @ 4.00Ghz, 32gb ram.

Numbers:

1. LLD (r331097): 4057ms, 4076ms, 4028ms
2. This patch: 3537ms, 3511ms, 3531ms.

> Part of the reason is a 12% regression on the number of instructions for scylla. Maybe that is because xxhash64 hashes 8 bytes at a time? Have you experimented with reading 8 bytes at a time?

It was slower for me. But I think it worth to retest. I am going to address the rest comments
so that it would be easy to switch between 4 and 8 bytes reading at a time and then will retest the difference between these 2.


https://reviews.llvm.org/D45571