perf: Avoid creating a SmallVec if nothing changes during a fold #68031

Marwes · 2020-01-08T22:26:37Z

Not sure if this helps but in theory it should be less work than what
the current micro optimization does for ty::Predicate lists.

(It would explain the overhead I am seeing from perf.)

Not sure if this helps but in theory it should be less work than what the current micro optimization does for `ty::Predicate` lists. (It would explain the overhead I am seeing from `perf`.)

rust-highfive · 2020-01-08T22:26:41Z

r? @estebank

(rust_highfive has picked a reviewer for you, use r? to override)

jonas-schievink · 2020-01-08T22:29:47Z

@bors try @rust-timer queue

rust-timer · 2020-01-08T22:29:48Z

Awaiting bors try build completion

bors · 2020-01-08T22:29:57Z

⌛ Trying commit a5657db with merge 5193414...

perf: Avoid creating a SmallVec if nothing changes during a fold Not sure if this helps but in theory it should be less work than what the current micro optimization does for `ty::Predicate` lists. (It would explain the overhead I am seeing from `perf`.)

jonas-schievink · 2020-01-08T22:30:36Z

src/librustc/ty/structural_impls.rs

@@ -1073,3 +1060,29 @@ impl<'tcx> TypeFoldable<'tcx> for InferConst<'tcx> {
        false
    }
 }
+
+fn fold_list<'tcx, F, T>(


Might be worth adding a comment here that explain that this is an optimization over .iter().map(...).collect()

Done in a1586f1

rust-highfive · 2020-01-08T22:54:21Z

The job x86_64-gnu-llvm-7 of your PR failed (pretty log, raw log). Through arcane magic we have determined that the following fragments from the build log may contain information about the problem.

Click to expand the log.

2020-01-08T22:27:12.9716594Z ##[command]git remote add origin https://github.com/rust-lang/rust
2020-01-08T22:27:12.9731229Z ##[command]git config gc.auto 0
2020-01-08T22:27:12.9734455Z ##[command]git config --get-all http.https://github.com/rust-lang/rust.extraheader
2020-01-08T22:27:12.9781187Z ##[command]git config --get-all http.proxy
2020-01-08T22:27:12.9786975Z ##[command]git -c http.extraheader="AUTHORIZATION: basic ***" fetch --force --tags --prune --progress --no-recurse-submodules --depth=2 origin +refs/heads/*:refs/remotes/origin/* +refs/pull/68031/merge:refs/remotes/pull/68031/merge
---
2020-01-08T22:53:50.1390775Z    Compiling cc v1.0.49
2020-01-08T22:53:50.1391190Z    Compiling core v0.0.0 (/checkout/src/libcore)
2020-01-08T22:53:55.4406678Z thread 'rustc' panicked at 'assertion failed: `(left == right)`
2020-01-08T22:53:55.4406906Z   left: `0`,
2020-01-08T22:53:55.4408055Z  right: `1`: destination and source slices have different lengths', /checkout/src/libcore/macros/mod.rs:18:13
2020-01-08T22:53:55.4408233Z 
2020-01-08T22:53:55.4408279Z error: internal compiler error: unexpected panic
2020-01-08T22:53:55.4408553Z 
2020-01-08T22:53:55.4424215Z note: the compiler unexpectedly panicked. this is a bug.
2020-01-08T22:53:55.4424215Z note: the compiler unexpectedly panicked. this is a bug.
2020-01-08T22:53:55.4424268Z 
2020-01-08T22:53:55.4425036Z note: we would appreciate a bug report: ***/blob/master/CONTRIBUTING.md#bug-reports
2020-01-08T22:53:55.4425093Z 
2020-01-08T22:53:55.4425453Z note: rustc 1.42.0-nightly (0ea29ce3e 2020-01-08) running on x86_64-unknown-linux-gnu
2020-01-08T22:53:55.4428839Z 
2020-01-08T22:53:55.4430932Z note: compiler flags: -Z external-macro-backtrace -Z binary-dep-depinfo -Z force-unstable-if-unmarked -C opt-level=2 -C codegen-units=1 -C debuginfo=0 -C link-args=-Wl,-rpath,$ORIGIN/../lib -C prefer-dynamic -C llvm-args=-import-instr-limit=10 -C debug-assertions=n --crate-type lib
2020-01-08T22:53:55.4434880Z note: some of the compiler flags provided by cargo are hidden
2020-01-08T22:53:55.4436013Z 
2020-01-08T22:53:55.4951605Z error: could not compile `core`.
2020-01-08T22:53:55.4970798Z warning: build failed, waiting for other jobs to finish...
---
2020-01-08T22:53:56.4329272Z   local time: Wed Jan  8 22:53:56 UTC 2020
2020-01-08T22:53:56.5279467Z   network time: Wed, 08 Jan 2020 22:53:56 GMT
2020-01-08T22:53:56.5283287Z == end clock drift check ==
2020-01-08T22:53:57.7401012Z 
2020-01-08T22:53:57.7528531Z ##[error]Bash exited with code '1'.
2020-01-08T22:53:57.7572343Z ##[section]Starting: Checkout
2020-01-08T22:53:57.7574427Z ==============================================================================
2020-01-08T22:53:57.7574508Z Task         : Get sources
2020-01-08T22:53:57.7574562Z Description  : Get sources from a repository. Supports Git, TfsVC, and SVN repositories.

I'm a bot! I can only do what humans tell me to, so if this was not helpful or you have suggestions for improvements, please ping or otherwise contact @TimNN. (Feature Requests)

rust-highfive · 2020-01-08T23:34:53Z

The job dist-x86_64-linux-alt of your PR failed (pretty log, raw log). Through arcane magic we have determined that the following fragments from the build log may contain information about the problem.

Click to expand the log.

2020-01-08T23:34:31.9457483Z    Compiling unwind v0.0.0 (/checkout/src/libunwind)
2020-01-08T23:34:33.6038547Z    Compiling backtrace-sys v0.1.32
2020-01-08T23:34:33.6724638Z thread 'rustc' panicked at 'assertion failed: `(left == right)`
2020-01-08T23:34:33.6732133Z   left: `0`,
2020-01-08T23:34:33.6732674Z  right: `1`: destination and source slices have different lengths', /rustc/5193414545ba1db55e954d1a68f1943cf4f258df/src/libcore/macros/mod.rs:18:13
2020-01-08T23:34:33.6732867Z 
2020-01-08T23:34:33.6732962Z error: internal compiler error: unexpected panic
2020-01-08T23:34:33.6733005Z 
2020-01-08T23:34:33.6733242Z note: the compiler unexpectedly panicked. this is a bug.
2020-01-08T23:34:33.6733242Z note: the compiler unexpectedly panicked. this is a bug.
2020-01-08T23:34:33.6733284Z 
2020-01-08T23:34:33.6734120Z note: we would appreciate a bug report: https://github.com/rust-lang/rust/blob/master/CONTRIBUTING.md#bug-reports
2020-01-08T23:34:33.6734180Z 
2020-01-08T23:34:33.6734420Z note: rustc 1.42.0-nightly (519341454 2020-01-08) running on x86_64-unknown-linux-gnu
2020-01-08T23:34:33.6734672Z 
2020-01-08T23:34:33.6735660Z note: compiler flags: -Z external-macro-backtrace -Z save-analysis -Z binary-dep-depinfo -Z force-unstable-if-unmarked -C opt-level=2 -C codegen-units=1 -C debuginfo=1 -C linker=clang -C link-args=-Wl,-rpath,$ORIGIN/../lib -C prefer-dynamic -C debug-assertions=n --crate-type lib
2020-01-08T23:34:33.6735893Z note: some of the compiler flags provided by cargo are hidden
2020-01-08T23:34:33.6735966Z 
2020-01-08T23:34:33.7603833Z    Compiling rustc_msan v0.0.0 (/checkout/src/librustc_msan)
2020-01-08T23:34:33.8232166Z    Compiling profiler_builtins v0.0.0 (/checkout/src/libprofiler_builtins)
---
2020-01-08T23:34:42.9178281Z   local time: Wed Jan  8 23:34:42 UTC 2020
2020-01-08T23:34:43.2460208Z   network time: Wed, 08 Jan 2020 23:34:43 GMT
2020-01-08T23:34:43.2461324Z == end clock drift check ==
2020-01-08T23:34:47.3871449Z 
2020-01-08T23:34:47.3989400Z ##[error]Bash exited with code '1'.
2020-01-08T23:34:47.4032290Z ##[section]Starting: Checkout
2020-01-08T23:34:47.4053823Z ==============================================================================
2020-01-08T23:34:47.4053930Z Task         : Get sources
2020-01-08T23:34:47.4054037Z Description  : Get sources from a repository. Supports Git, TfsVC, and SVN repositories.

I'm a bot! I can only do what humans tell me to, so if this was not helpful or you have suggestions for improvements, please ping or otherwise contact @TimNN. (Feature Requests)

bors · 2020-01-08T23:35:08Z

💔 Test failed - checks-azure

Marwes · 2020-01-15T10:07:02Z

This could use a perf run now.

estebank · 2020-01-16T23:23:06Z

@bors try @rust-timer queue

rust-timer · 2020-01-16T23:23:08Z

Awaiting bors try build completion

bors · 2020-01-16T23:23:19Z

⌛ Trying commit a1586f1 with merge 64c086d...

perf: Avoid creating a SmallVec if nothing changes during a fold Not sure if this helps but in theory it should be less work than what the current micro optimization does for `ty::Predicate` lists. (It would explain the overhead I am seeing from `perf`.)

bors · 2020-01-17T02:23:51Z

☀️ Try build successful - checks-azure
Build commit: 64c086d (64c086d8ce1317f2d12547b9ea04989363c0cae6)

rust-timer · 2020-01-17T02:23:53Z

Queued 64c086d with parent 4884061, future comparison URL.

rust-timer · 2020-01-17T06:58:16Z

Finished benchmarking try commit 64c086d, comparison URL.

Marwes · 2020-01-22T14:09:12Z

Perf results look good. Should be good to merge?

estebank · 2020-01-26T00:41:46Z

@bors r+

bors · 2020-01-26T00:41:47Z

📌 Commit a1586f1 has been approved by estebank

bors · 2020-01-26T01:51:57Z

⌛ Testing commit a1586f1 with merge 086b2a4...

perf: Avoid creating a SmallVec if nothing changes during a fold Not sure if this helps but in theory it should be less work than what the current micro optimization does for `ty::Predicate` lists. (It would explain the overhead I am seeing from `perf`.)

bors · 2020-01-26T05:13:08Z

☀️ Test successful - checks-azure
Approved by: estebank
Pushing 086b2a4 to master...

perf: Avoid creating a SmallVec if nothing changes during a fold

a5657db

Not sure if this helps but in theory it should be less work than what the current micro optimization does for `ty::Predicate` lists. (It would explain the overhead I am seeing from `perf`.)

rust-highfive assigned estebank Jan 8, 2020

rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Jan 8, 2020

jonas-schievink reviewed Jan 8, 2020

View reviewed changes

bors added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Jan 8, 2020

Marwes added 2 commits January 9, 2020 07:45

Fix copy_from_slice which should be extend_from_slice

898ed63

Explain fold_list

a1586f1

bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Jan 26, 2020

bors added the merged-by-bors This PR was explicitly merged by bors. label Jan 26, 2020

bors merged commit a1586f1 into rust-lang:master Jan 26, 2020

Marwes deleted the fold_list branch January 26, 2020 08:36

perf: Avoid creating a SmallVec if nothing changes during a fold #68031

perf: Avoid creating a SmallVec if nothing changes during a fold #68031

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