Optimize StringTableBuilder.
This is a patch to improve StringTableBuilder's performance. That class'
finalize function is very hot particularly in LLD because the function
does tail-merge strings in string tables or SHF_MERGE sections.
Generic std::sort-style sorter is not efficient for sorting strings.
The function implemented in this patch seems to be more efficient.
Here's a benchmark of LLD to link Clang with or without this patch.
The numbers are medians of 50 runs.
-O0
real 0m0.455s
real 0m0.430s (5.5% faster)
-O3
real 0m0.487s
real 0m0.452s (7.2% faster)
Since that is a benchmark of the whole linker, the speedup of
StringTableBuilder itself is much more than that.
http://reviews.llvm.org/D14053
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@251337
91177308-0d34-0410-b5e6-
96231b3b80d8
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