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authorDylan DPC <dylan.dpc@gmail.com>2021-03-08 13:13:18 +0100
committerGitHub <noreply@github.com>2021-03-08 13:13:18 +0100
commitda74a77622b29c056fa5a18f6e6033d9579a0e90 (patch)
treefe0f4554add4289d953078631bf8d6909facc44a /compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp
parent27885a94c6a6c98a0d49af3962f1218adcd6efd2 (diff)
parent6a679ffc8125419123e416fbeb14a4e118e9f366 (diff)
downloadrust-da74a77622b29c056fa5a18f6e6033d9579a0e90.tar.gz
rust-da74a77622b29c056fa5a18f6e6033d9579a0e90.zip
Rollup merge of #82047 - the8472:fast-rename, r=davidtwco
bypass auto_da_alloc for metadata files

This saves about 0.7% when rerunning the UI test suite. I.e. when the metadata files exist and will be overwritten. No improvements expected for a clean build. So it might show up in incr-patched perf results.
```
regular rename:

Benchmark #1: touch src/tools/compiletest/src/main.rs ; RUSTC_WRAPPER="" schedtool -B -e ./x.py test src/test/ui
  Time (mean ± σ):     47.305 s ±  0.170 s    [User: 1631.540 s, System: 412.648 s]
  Range (min … max):   47.125 s … 47.856 s    20 runs

non-durable rename:

Benchmark #1: touch src/tools/compiletest/src/main.rs ; RUSTC_WRAPPER="" schedtool -B -e ./x.py test src/test/ui
  Time (mean ± σ):     46.930 s ±  0.064 s    [User: 1634.344 s, System: 396.038 s]
  Range (min … max):   46.759 s … 47.043 s    20 runs
```

There are more places that trigger auto_da_alloc behavior by overwriting existing files with O_TRUNC, but those are much harder to locate because `O_TRUNC` is set on `open()` but the writeback is triggered on `close()`. The latter is the part which shows up in profiles.
Diffstat (limited to 'compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp')
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