tree 138d4ae881be77eb7b03750776fb20e988928804
parent 0625da07ece7b1a374ec0719b6f40ebe3d0950c1
author Philipp Wollermann <philwo@google.com> 1788904689 +0200
committer gn-scoped@luci-project-accounts.iam.gserviceaccount.com <gn-scoped@luci-project-accounts.iam.gserviceaccount.com> 1789122622 -0700

Header check: avoid interning paths during include lookup

Resolving each include against each include directory constructs a
SourceFile, which interns the candidate path even when lookup fails.
This adds allocations and contention on the shared interning lock.

Use a hash map keyed by path string views. Normalize candidate paths
in a reusable buffer, look them up directly, and return the SourceFile
stored in the matching entry.

Chromium `gn gen --check`, medians of five round-robin rounds:
  Mac (M4 Max):    3.91 s -> 3.16 s
  GCE c4d-384:     7.71 s -> 5.96 s
  Intel 13900KS:   4.11 s -> 3.42 s

CPU time (c4d-standard-384):
  User:  43.8 s -> 40.0 s (-9%)
  Sys:  121.1 s -> 53.0 s (-56%)

Heap stats:
  Allocs (count):  64.84 M -> 55.16 M (-15%)
  Heap (total):    26.27 GB -> 25.58 GB (-3%)
  Heap (peak):      5.95 GB ->  5.74 GB (-4%)

Change-Id: Iefb962d72efcba69361bccce430e41d10a63c2a9
Reviewed-on: https://gn-review.googlesource.com/c/gn/+/26320
Reviewed-by: Takuto Ikuta <tikuta@google.com>
Commit-Queue: Philipp Wollermann <philwo@google.com>