[all-commits] [llvm/llvm-project] 75ea78: [DebugNames] Compare TableEntry names more efficie...

[Felipe de Azevedo Piovezan via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 75ea78ab677f8357aa14fd4c0aff5d551a4ff8aa
      https://github.com/llvm/llvm-project/commit/75ea78ab677f8357aa14fd4c0aff5d551a4ff8aa
  Author: Felipe de Azevedo Piovezan <fpiovezan at apple.com>
  Date:   2024-01-30 (Tue, 30 Jan 2024)

  Changed paths:
    M llvm/include/llvm/DebugInfo/DWARF/DWARFAcceleratorTable.h
    M llvm/lib/DebugInfo/DWARF/DWARFAcceleratorTable.cpp

  Log Message:
  -----------
  [DebugNames] Compare TableEntry names more efficiently (#79759)

TableEntry names are pointers into the string table section, and
accessing their
length requires a search for `\0`. However, 99% of the time we only need
to
compare the name against some other other, and such a comparison will
fail as
early as the first character.

This commit adds a method to the interface of TableEntry so that such a
comparison can be done without extracting the full name. It saves 10% in
the
time (1250ms -> 1100 ms) to evaluate the following expression.

```
lldb \
  --batch \
  -o "b CodeGenFunction::GenerateCode" \
  -o run \
  -o "expr Fn" \
  -- \
  clang++ -c -g test.cpp -o /dev/null &> output
```