[llvm-bugs] [Bug 37029] New: xxhash64 probably not the best choice for SHF_MERGE merging

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=37029

            Bug ID: 37029
           Summary: xxhash64 probably not the best choice for SHF_MERGE
                    merging
           Product: lld
           Version: unspecified
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: ELF
          Assignee: unassignedbugs at nondot.org
          Reporter: rafael at espindo.la
                CC: llvm-bugs at lists.llvm.org

As a quick experiment I replaced the two calls to xxhash64 in splitIntoPieces
with hash_value. This resulted in a 4% speedup when linking scylla.

While xxHash64 was 13.3% of the runtime of master, hash_combine is just 6.6% of
the patch.

We can't just use hash_combine since it produces different results on 32 bit
hosts, but refactoring the algorithm to have the option of a stable result is
probably worth it.

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