| Issue |
172266
|
| Summary |
16% compile-time slowdown after clang #161671
|
| Labels |
clang:frontend
|
| Assignees |
|
| Reporter |
zmodem
|
Filing as a proper bug so we don't lose track of this.
Chromium reported a 16% build time slowdown after https://github.com/llvm/llvm-project/pull/161671 That includes linking and other build actions, so the average compiler slowdown is probably a little higher.
When bootstrapping Clang with `-DCMAKE_CXX_STANDARD=20`, we only measured an 1.5% regression (https://github.com/llvm/llvm-project/pull/161671#issuecomment-3442833336), so projects are probably differently affected depending on their use of c++ features.
Code that's especially affected by this is *badly* affected however. For example, https://github.com/llvm/llvm-project/pull/161671#issuecomment-3533372315 shows a 140% slowdown, and there is lots more like it.
It would be great if we could fix or at least mitigate this before Clang 22 -- or if that's not possible, give some guidance on source mitigations to avoid the slowdown.
@zyn0217 @cor3ntin @AaronBallman
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