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Avoid allocating when parsing \u{...} literals. - #50052

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Apr 20, 2018
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Avoid allocating when parsing \u{...} literals.#50052
bors merged 1 commit into
rust-lang:masterfrom
nnethercote:char_lit

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@nnethercotennethercote commented Apr 18, 2018•
edited by kennytm
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char_lit uses an allocation in order to ignore '_' chars in \u{...}
literals. This patch changes it to not do that by processing the chars
more directly.

This improves various rustc-perf benchmark measurements by up to 6%,
particularly regex, futures, clap, coercions, hyper, and encoding.

rustc-perf results, on a stage 2 build with jemalloc disabled:

Details
regex-check
avg: -5.4%	min: -6.5%	max: -2.7%
futures-check
avg: -3.5%	min: -5.3%	max: -1.7%
regex-opt
avg: -2.0%	min: -5.1%	max: -0.2%
regex
avg: -2.3%	min: -5.0%	max: -0.6%
futures-opt
avg: -3.0%	min: -4.8%	max: -1.1%
futures
avg: -3.1%	min: -4.8%	max: -1.3%
clap-rs-check
avg: -1.8%	min: -3.5%	max: -0.9%
coercions-check
avg: -2.0%	min: -3.3%	max: -1.0%
hyper-check
avg: -2.2%	min: -3.1%	max: -1.3%
hyper
avg: -1.3%	min: -2.4%	max: -0.3%
hyper-opt
avg: -0.9%	min: -2.3%	max: -0.1%
coercions
avg: -1.1%	min: -2.2%	max: -0.4%
encoding-check
avg: -1.7%	min: -2.2%	max: -0.9%
clap-rs-opt
avg: -0.7%	min: -2.2%	max: 0.0%
coercions-opt
avg: -1.2%	min: -2.1%	max: -0.3%
clap-rs
avg: -0.8%	min: -1.9%	max: -0.4%
encoding-opt
avg: -1.0%	min: -1.9%	max: -0.3%
encoding
avg: -1.1%	min: -1.9%	max: -0.4%
piston-image-check
avg: -0.7%	min: -1.3%	max: -0.3%
inflate-opt
avg: -0.3%	min: -0.9%	max: -0.0%
piston-image
avg: -0.3%	min: -0.8%	max: -0.1%
piston-image-opt
avg: -0.3%	min: -0.7%	max: -0.1%
syn-check
avg: -0.3%	min: -0.6%	max: -0.1%
deep-vector
avg: 0.1%	min: -0.1%	max: 0.5%
syn-opt
avg: -0.1%	min: -0.4%	max: 0.0%
html5ever
avg: -0.2%	min: -0.4%	max: -0.0%
deep-vector-check
avg: 0.0%	min: -0.3%	max: 0.3%
syn
avg: -0.2%	min: -0.3%	max: -0.1%
html5ever-check
avg: -0.3%	min: -0.3%	max: -0.2%
issue-46449-check
avg: -0.1%	min: -0.2%	max: 0.2%
html5ever-opt
avg: -0.0%	min: -0.2%	max: 0.1%
deep-vector-opt
avg: -0.0%	min: -0.2%	max: 0.1%
issue-46449-opt
avg: -0.0%	min: -0.2%	max: 0.1%
unify-linearly-check
avg: -0.0%	min: -0.2%	max: 0.1%
helloworld-check
avg: 0.0%	min: -0.0%	max: 0.2%
parser-check
avg: -0.0%	min: -0.2%	max: 0.0%
inflate
avg: 0.0%	min: -0.0%	max: 0.1%
tokio-webpush-simple-check
avg: -0.1%	min: -0.1%	max: -0.0%
regression-31157-check
avg: 0.0%	min: -0.1%	max: 0.1%
issue-46449
avg: 0.0%	min: -0.1%	max: 0.1%
tuple-stress-opt
avg: 0.0%	min: -0.0%	max: 0.1%
tuple-stress-check
avg: -0.0%	min: -0.1%	max: 0.1%
tuple-stress
avg: 0.0%	min: -0.0%	max: 0.1%
deeply-nested-check
avg: 0.0%	min: -0.0%	max: 0.1%
regression-31157
avg: -0.0%	min: -0.1%	max: 0.1%
deeply-nested-opt
avg: -0.0%	min: -0.1%	max: 0.1%
parser-opt
avg: -0.0%	min: -0.1%	max: 0.0%
parser
avg: 0.1%	min: 0.0%	max: 0.1%
tokio-webpush-simple
avg: -0.0%	min: -0.1%	max: 0.1%
regression-31157-opt
avg: -0.0%	min: -0.1%	max: 0.1%
helloworld-opt
avg: 0.0%	min: -0.0%	max: 0.1%
unify-linearly-opt
avg: 0.0%	min: -0.0%	max: 0.1%
unused-warnings-check
avg: 0.0%	min: 0.0%	max: 0.1%
tokio-webpush-simple-opt
avg: -0.0%	min: -0.1%	max: 0.0%
helloworld
avg: -0.0%	min: -0.0%	max: 0.1%
unused-warnings
avg: 0.0%	min: -0.0%	max: 0.0%
deeply-nested
avg: -0.0%	min: -0.0%	max: -0.0%
unused-warnings-opt
avg: 0.0%	min: -0.0%	max: 0.0%
unify-linearly
avg: 0.0%	min: -0.0%	max: 0.0%
inflate-check
avg: 0.0%	min: -0.0%	max: 0.0%

@kennytm

kennytm commented Apr 18, 2018

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Could we do the same for the integer_lit function too 🤔

@kennytmkennytm added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Apr 18, 2018
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Mark-Simulacrum commented Apr 18, 2018

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@bors try

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bors commented Apr 18, 2018

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⌛ Trying commit ca47fdc00059278c920df9743d84758dac533a32 with merge 1d4dcc78c0dfae72827cd04a442c6bd9e9c89ce2...

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☀️ Test successful - status-travis
State: approved= try=True

leonardo-m
leonardo-m reviewed Apr 18, 2018
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Comment threadsrc/libsyntax/parse/mod.rs Outdated

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Why not just lit[3..idx].bytes() {

@nnethercotennethercoteApr 18, 2018

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Ok.

leonardo-m
leonardo-m reviewed Apr 18, 2018
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Comment threadsrc/libsyntax/parse/mod.rs Outdated

@leonardo-mleonardo-mApr 18, 2018•
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Why don't you replace that hard cast "as" with:

let c = char::from(c);

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Ok.

@nnethercote

nnethercote commented Apr 18, 2018

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Could we do the same for the integer_lit function too thinking

char_lit is much hotter, but I see in my profiles that integer_lit is moderately hot for a couple of benchmarks. So I'll do that too.

@nnethercote

nnethercote commented Apr 18, 2018

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Actually,integer_lit is a bit harder, so I'd prefer to do that in a follow-up.

@nnethercote
Avoid allocating when parsing \u{...} literals.
9f14502
`char_lit` uses an allocation in order to ignore '_' chars in \u{...}
literals. This patch changes it to not do that by processing the chars
more directly.
This improves various rustc-perf benchmark measurements by up to 6%,
particularly regex, futures, clap, coercions, hyper, and encoding.
@nnethercote

nnethercote commented Apr 18, 2018

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The new patch addresses @leonardo-m's comments.

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Mark-Simulacrum commented Apr 18, 2018

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@bors r+

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bors commented Apr 18, 2018

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📌 Commit 9f14502 has been approved by Mark-Simulacrum

@borsbors 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-review Status: Awaiting review from the assignee but also interested parties. labels Apr 18, 2018
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⌛ Testing commit 9f14502 with merge f6e532b8b41298b6adb04d6254e660cd7a5abb38...

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💔 Test failed - status-travis

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@nnethercote

nnethercote commented Apr 20, 2018

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Could this be an infrastructure issue? I don't see anything else obviously wrong...

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kennytm commented Apr 20, 2018

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@bors retry

[00:01:44] Compiling syn v0.13.1
No output has been received in the last 30m0s, this potentially indicates a stalled build or something wrong with the build itself.

@borsbors 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-review Status: Awaiting review from the assignee but also interested parties. labels Apr 20, 2018
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⌛ Testing commit 9f14502 with merge 85f5dd4...

bors added a commit that referenced this pull request Apr 20, 2018
@bors
Auto merge of#50052- nnethercote:char_lit, r=Mark-Simulacrum
85f5dd4
Avoid allocating when parsing \u{...} literals.
`char_lit` uses an allocation in order to ignore '_' chars in \u{...}
literals. This patch changes it to not do that by processing the chars
more directly.
This improves various rustc-perf benchmark measurements by up to 6%,
particularly regex, futures, clap, coercions, hyper, and encoding.
rustc-perf results, on a stage 2 build with jemalloc disabled:
<details>
```
regex-check
avg: -5.4%	min: -6.5%	max: -2.7%
futures-check
avg: -3.5%	min: -5.3%	max: -1.7%
regex-opt
avg: -2.0%	min: -5.1%	max: -0.2%
regex
avg: -2.3%	min: -5.0%	max: -0.6%
futures-opt
avg: -3.0%	min: -4.8%	max: -1.1%
futures
avg: -3.1%	min: -4.8%	max: -1.3%
clap-rs-check
avg: -1.8%	min: -3.5%	max: -0.9%
coercions-check
avg: -2.0%	min: -3.3%	max: -1.0%
hyper-check
avg: -2.2%	min: -3.1%	max: -1.3%
hyper
avg: -1.3%	min: -2.4%	max: -0.3%
hyper-opt
avg: -0.9%	min: -2.3%	max: -0.1%
coercions
avg: -1.1%	min: -2.2%	max: -0.4%
encoding-check
avg: -1.7%	min: -2.2%	max: -0.9%
clap-rs-opt
avg: -0.7%	min: -2.2%	max: 0.0%
coercions-opt
avg: -1.2%	min: -2.1%	max: -0.3%
clap-rs
avg: -0.8%	min: -1.9%	max: -0.4%
encoding-opt
avg: -1.0%	min: -1.9%	max: -0.3%
encoding
avg: -1.1%	min: -1.9%	max: -0.4%
piston-image-check
avg: -0.7%	min: -1.3%	max: -0.3%
inflate-opt
avg: -0.3%	min: -0.9%	max: -0.0%
piston-image
avg: -0.3%	min: -0.8%	max: -0.1%
piston-image-opt
avg: -0.3%	min: -0.7%	max: -0.1%
syn-check
avg: -0.3%	min: -0.6%	max: -0.1%
deep-vector
avg: 0.1%	min: -0.1%	max: 0.5%
syn-opt
avg: -0.1%	min: -0.4%	max: 0.0%
html5ever
avg: -0.2%	min: -0.4%	max: -0.0%
deep-vector-check
avg: 0.0%	min: -0.3%	max: 0.3%
syn
avg: -0.2%	min: -0.3%	max: -0.1%
html5ever-check
avg: -0.3%	min: -0.3%	max: -0.2%
issue-46449-check
avg: -0.1%	min: -0.2%	max: 0.2%
html5ever-opt
avg: -0.0%	min: -0.2%	max: 0.1%
deep-vector-opt
avg: -0.0%	min: -0.2%	max: 0.1%
issue-46449-opt
avg: -0.0%	min: -0.2%	max: 0.1%
unify-linearly-check
avg: -0.0%	min: -0.2%	max: 0.1%
helloworld-check
avg: 0.0%	min: -0.0%	max: 0.2%
parser-check
avg: -0.0%	min: -0.2%	max: 0.0%
inflate
avg: 0.0%	min: -0.0%	max: 0.1%
tokio-webpush-simple-check
avg: -0.1%	min: -0.1%	max: -0.0%
regression-31157-check
avg: 0.0%	min: -0.1%	max: 0.1%
issue-46449
avg: 0.0%	min: -0.1%	max: 0.1%
tuple-stress-opt
avg: 0.0%	min: -0.0%	max: 0.1%
tuple-stress-check
avg: -0.0%	min: -0.1%	max: 0.1%
tuple-stress
avg: 0.0%	min: -0.0%	max: 0.1%
deeply-nested-check
avg: 0.0%	min: -0.0%	max: 0.1%
regression-31157
avg: -0.0%	min: -0.1%	max: 0.1%
deeply-nested-opt
avg: -0.0%	min: -0.1%	max: 0.1%
parser-opt
avg: -0.0%	min: -0.1%	max: 0.0%
parser
avg: 0.1%	min: 0.0%	max: 0.1%
tokio-webpush-simple
avg: -0.0%	min: -0.1%	max: 0.1%
regression-31157-opt
avg: -0.0%	min: -0.1%	max: 0.1%
helloworld-opt
avg: 0.0%	min: -0.0%	max: 0.1%
unify-linearly-opt
avg: 0.0%	min: -0.0%	max: 0.1%
unused-warnings-check
avg: 0.0%	min: 0.0%	max: 0.1%
tokio-webpush-simple-opt
avg: -0.0%	min: -0.1%	max: 0.0%
helloworld
avg: -0.0%	min: -0.0%	max: 0.1%
unused-warnings
avg: 0.0%	min: -0.0%	max: 0.0%
deeply-nested
avg: -0.0%	min: -0.0%	max: -0.0%
unused-warnings-opt
avg: 0.0%	min: -0.0%	max: 0.0%
unify-linearly
avg: 0.0%	min: -0.0%	max: 0.0%
inflate-check
avg: 0.0%	min: -0.0%	max: 0.0%
```
</details>
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bors commented Apr 20, 2018

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☀️ Test successful - status-appveyor, status-travis
Approved by: Mark-Simulacrum
Pushing 85f5dd4 to master...

@bors
bors merged commit 9f14502 into rust-lang:masterApr 20, 2018
@nnethercote
nnethercote deleted the char_lit branch April 23, 2018 05:10
@nnethercotennethercote mentioned this pull request Aug 20, 2018
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@nnethercote

nnethercote commented Oct 29, 2018

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Actually,integer_lit is a bit harder, so I'd prefer to do that in a follow-up.

I finally did integer_lit (and float_lit) in #55384.

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