[all-commits] [llvm/llvm-project] 8fd56e: [clang][deps] NFC: Speed up canonical context hash...

[Jan Svoboda via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 8fd56ea11256f220502fe9819b496b15582f8d1e
      https://github.com/llvm/llvm-project/commit/8fd56ea11256f220502fe9819b496b15582f8d1e
  Author: Jan Svoboda <jan_svoboda at apple.com>
  Date:   2023-08-03 (Thu, 03 Aug 2023)

  Changed paths:
    M clang/lib/Tooling/DependencyScanning/ModuleDepCollector.cpp

  Log Message:
  -----------
  [clang][deps] NFC: Speed up canonical context hash computation

This patch makes use of the infrastructure established in D157046 to speed up computation of the canonical context hash in the dependency scanner. This is somewhat hot code, since it's ran for all modules in the dependency graph of every TU.

I also tried an alternative approach that tried to avoid allocations as much as possible (essentially doing `HashBuilder.add(Arg.toStringRef(ArgVec))`), but that turned out to be slower than approach in this patch.

Note that this is not problematic in the same way command-line hashing used to be prior D143027. The lambda is now being called even for constant strings.

Depends on D157046.

Reviewed By: benlangmuir

Differential Revision: https://reviews.llvm.org/D157052