[-Wunsafe-buffer-usage] Reland '[Clang] Optimize -Wunsafe-buffer-usage (#125492)' #10340
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llvm#125492)' [Clang] Optimize -Wunsafe-buffer-usage. (llvm#125492) The Clang disgnostic `-Wunsafe-buffer-usage` was adding up to +15% compilation time when used. Profiling showed that most of the overhead comes from the use of ASTMatchers. This change replaces the ASTMatcher infrastructure with simple matching functions and keeps the functionality unchanged. It reduces the overhead added by `-Wunsafe-buffer-usage` by 87.8%, leaving a negligible additional compilation time of 1.7% when the diagnostic is used. **Old version without -Wunsafe-buffer-usage:** ``` $ hyperfine -i -w 1 --runs 5 '/tmp/old_clang -c -std=c++20 /tmp/preprocessed.cc -ferror-limit=20' Benchmark 1: /tmp/old_clang -c -std=c++20 /tmp/preprocessed.cc -ferror-limit=20 Time (mean ± σ): 231.035 s ± 3.210 s [User: 229.134 s, System: 1.704 s] Range (min … max): 228.751 s … 236.682 s 5 runs ``` **Old version with -Wunsafe-buffer-usage:** ``` $ hyperfine -i -w 1 --runs 10 '/tmp/old_clang -c -std=c++20 /tmp/preprocessed.cc -ferror-limit=20 -Wunsafe-buffer-usage' Benchmark 1: /tmp/old_clang -c -std=c++20 /tmp/preprocessed.cc -ferror-limit=20 -Wunsafe-buffer-usage Time (mean ± σ): 263.840 s ± 0.854 s [User: 262.043 s, System: 1.575 s] Range (min … max): 262.442 s … 265.142 s 10 runs ``` **New version with -Wunsafe-buffer-usage:** ``` $ hyperfine -i -w 1 --runs 10 '/tmp/new_clang -c -std=c++20 /tmp/preprocessed.cc -ferror-limit=20 -Wunsafe-buffer-usage' Benchmark 1: /tmp/new_clang -c -std=c++20 /tmp/preprocessed.cc -ferror-limit=20 -Wunsafe-buffer-usage Time (mean ± σ): 235.169 s ± 1.408 s [User: 233.406 s, System: 1.561 s] Range (min … max): 232.221 s … 236.792 s 10 runs ``` Conflicts: clang/lib/Analysis/UnsafeBufferUsage.cpp [-Wunsafe-buffer-usage] Correctly merge "[Clang] Optimize -Wunsafe-buffer-usage" The upstream commit 18a0bd4fc387e16c4bd342c6d3a83366e2ec2bc1 replaces ASTMatchers in `UnsafeBufferUsage.cpp` with plain AST matching. It improves the performance and makes the code easier to debug and optimize. This commit resolves massive conflicts introduced in 18a0bd4fc387e16c4bd342c6d3a83366e2ec2bc1. (rdar://147529568)
ziqingluo-90
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Mar 25, 2025
#10340 introduces a build issue on Linux: https://ci.swift.org/job/pr-apple-llvm-project-llvm-linux/666/consoleFull This commit fixes it.
ziqingluo-90
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Mar 25, 2025
#10340 introduces a build issue on Linux: https://ci.swift.org/job/pr-apple-llvm-project-llvm-linux/666/consoleFull This commit fixes it.
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Manually merge '[Clang] Optimize -Wunsafe-buffer-usage. (llvm#125492)'
(rdar://147529568)