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| author | bors <bors@rust-lang.org> | 2020-09-22 00:22:24 +0000 |
|---|---|---|
| committer | bors <bors@rust-lang.org> | 2020-09-22 00:22:24 +0000 |
| commit | 45198456be60a6906d24abdc3c67a31b9206188e (patch) | |
| tree | ab3f0e63d941c5d2f205312d195ccf696d1a4731 /compiler/rustc_mir/src/transform/coverage/debug.rs | |
| parent | f47df31ae5d7d9795399dca3a0003c1856900361 (diff) | |
| parent | ab83d372ed5b1799d418afe83c468e4c5973cc34 (diff) | |
| download | rust-45198456be60a6906d24abdc3c67a31b9206188e.tar.gz rust-45198456be60a6906d24abdc3c67a31b9206188e.zip | |
Auto merge of #76913 - vandenheuvel:performance_debug, r=lcnr
Fixing the performance regression of #76244 Issue https://github.com/rust-lang/rust/issues/74865 suggested that removing the `def_id` field from `ParamEnv` would improve performance. PR https://github.com/rust-lang/rust/pull/76244 implemented this change. Generally, [results](https://perf.rust-lang.org/compare.html?start=80fc9b0ecb29050d45b17c64af004200afd3cfc2&end=5ef250dd2ad618ee339f165e9b711a1b4746887d) were as expected: an instruction count decrease of about a percent. The instruction count for the unicode crates increased by about 3%, which `@nnethercote` speculated to be caused by a quirk of inlining or codegen. As the results were generally positive, and for chalk integration, this was also a step in the right direction, the PR was r+'d regardless. However, [wall-time performance results](https://perf.rust-lang.org/compare.html?start=a055c5a1bd95e029e9b31891db63b6dc8258b472&end=7402a394471a6738a40fea7d4f1891666e5a80c5&stat=task-clock) show a much larger performance degradation: 25%, as [mentioned](https://github.com/rust-lang/rust/pull/76244#issuecomment-694459840) by `@Mark-Simulacrum.` This PR, for now, reverts #76244 and attempts to find out, which change caused the regression.
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