Do not use LEB128 for encoding u16 and i16

[Kobzol]

An experiment to try out the suggestion from #68779.

Closes: #68779

[rust-highfive]

r? @michaelwoerister

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[camelid]

@bors try @rust-timer queue

[rust-timer]

Awaiting bors try build completion.

@rustbot label: +S-waiting-on-perf

[bors]

⌛ Trying commit b11dc2108beb5dda9b6249d76fae83bfeb8f5249 with merge 12ca1781010a9ea74d60a1feba203098b7102bd9...

[bors]

☀️ Try build successful - checks-actions
Build commit: 12ca1781010a9ea74d60a1feba203098b7102bd9 (12ca1781010a9ea74d60a1feba203098b7102bd9)

[rust-timer]

Queued 12ca1781010a9ea74d60a1feba203098b7102bd9 with parent f8abed9, future comparison URL.

[rust-timer]

Finished benchmarking commit (12ca1781010a9ea74d60a1feba203098b7102bd9): comparison url.

Summary: This change led to moderate relevant improvements 🎉 in compiler performance.

• Moderate improvement in instruction counts (up to -2.1% on incr-unchanged builds of helloworld)

If you disagree with this performance assessment, please file an issue in rust-lang/rustc-perf.

Benchmarking this pull request likely means that it is perf-sensitive, so we're automatically marking it as not fit for rolling up. While you can manually mark this PR as fit for rollup, we strongly recommend not doing so since this PR led to changes in compiler perf.

@bors rollup=never
@rustbot label: +S-waiting-on-review -S-waiting-on-perf -perf-regression

[camelid]

Looks like artifact sizes increased a bit, though not much, as expected. E.g. https://perf.rust-lang.org/detailed-query.html?commit=12ca1781010a9ea74d60a1feba203098b7102bd9&base_commit=f8abed9ed48bace6be0087bcd44ed534e239b8d8&benchmark=ripgrep-check&scenario=incr-unchanged

[Kobzol]

I refactored the code to remove unsafe.

[michaelwoerister]

Looks good to me, thanks @Kobzol!

@bors r+

[bors]

📌 Commit 6c9ffe4 has been approved by michaelwoerister

[bors]

⌛ Testing commit 6c9ffe4 with merge 8618053cebad3af83f6ef781d14db198c5e053a7...

[rust-log-analyzer]

A job failed! Check out the build log: (web) (plain)

Click to see the possible cause of the failure (guessed by this bot)

[bors]

💔 Test failed - checks-actions

[Aaron1011]

@bors retry

[bors]

⌛ Testing commit 6c9ffe4 with merge 399ba6b...

[bors]

☀️ Test successful - checks-actions
Approved by: michaelwoerister
Pushing 399ba6b to master...

[rust-timer]

Finished benchmarking commit (399ba6b): comparison url.

Summary: This benchmark run did not return any relevant changes.

If you disagree with this performance assessment, please file an issue in rust-lang/rustc-perf.

@rustbot label: -perf-regression