rustc_metadata: Encode even less doc comments

[petrochenkov]

The fact that def_id is in the tcx.privacy_access_levels(()) table is not very meaningful, especially after #102026, is_exported (or is_reachable in the worst case) is what you need.

Follow up to #98450.
r? @GuillaumeGomez @lqd

[lqd]

r=me if a perf run comes back clean

The reachability query however, was too much of a pessimization for incremental runs, when it was tried on the previous PR.

[petrochenkov]

@bors try @rust-timer queue

[rust-timer]

Awaiting bors try build completion.

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

[bors]

⌛ Trying commit cd0977e2d8b58f702e1fafc0e794a238263aaf1f with merge 925fac1518f23cd489a35e7f477a78539f1a475c...

[bors]

☀️ Try build successful - checks-actions
Build commit: 925fac1518f23cd489a35e7f477a78539f1a475c (925fac1518f23cd489a35e7f477a78539f1a475c)

[rust-timer]

Queued 925fac1518f23cd489a35e7f477a78539f1a475c with parent c07a6a9, future comparison URL.

[rust-timer]

Finished benchmarking commit (925fac1518f23cd489a35e7f477a78539f1a475c): comparison URL.

Overall result: ❌✅ regressions and improvements - no action needed

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 may lead to changes in compiler perf.

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

Instruction count

This is a highly reliable metric that was used to determine the overall result at the top of this comment.

	mean1	range	count2
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	0.1%	[0.1%, 0.1%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.2%	[-0.2%, -0.2%]	1
All ❌✅ (primary)	-	-	0

Max RSS (memory usage)

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean1	range	count2
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	4.3%	[2.4%, 5.6%]	3
Improvements ✅ (primary)	-1.4%	[-1.6%, -1.3%]	2
Improvements ✅ (secondary)	-2.6%	[-2.6%, -2.6%]	1
All ❌✅ (primary)	-1.4%	[-1.6%, -1.3%]	2

Cycles

This benchmark run did not return any relevant results for this metric.

Footnotes

1. the arithmetic mean of the percent change ↩ ↩²

2. number of relevant changes ↩ ↩²

[petrochenkov]

Consistent improvements in metadata size https://perf.rust-lang.org/compare.html?start=c07a6a9c0c6c571d535de74d7ec28469fba46e37&end=925fac1518f23cd489a35e7f477a78539f1a475c&stat=size%3Acrate_metadata
@bors r=lqd

[bors]

📌 Commit cd0977e2d8b58f702e1fafc0e794a238263aaf1f has been approved by lqd

It is now in the queue for this repository.

[lqd]

Awesome, thanks a bunch @petrochenkov.

What I was particularly interested in the previous work was the impact on libstd/libcore (with the eventual goal of removing more of the unused/unexpected metadata), and on x86_64-unknown-linux-gnu we see from pre-#98450 to this PR:

item	nightly-2022-10-20	nightly with #98450	this PR	total
libstd.rmeta	10652720	10363296	10142392	-4.8%
libcore.rmeta	60157032	59557024	59435328	-1.2%
libstd.rlib	20904980	20614708	20394284	-2.4%
libcore.rlib	64008136	63413340	63286316	-1.1%

Most of libcore's doc comments are surely exported anyways (stdarch's intel intrinsics), but that's another nice improvement on libstd. Getting the rest of the way to the expected >= 15% on libstd, and >= 10% on libcore will require finding a way to have tool-specific metadata either out of band, computed on demand via -Zbuild-std, or a different mechanism (maybe related to miri's custom sysroot build, in case it's not using build-std and/or xargo).

[petrochenkov]

@bors r=lqd

[bors]

📌 Commit d080532 has been approved by lqd

It is now in the queue for this repository.

[bors]

⌛ Testing commit d080532 with merge b3379a02362387aa52e162391500aeaadc04ab80...

[bors]

💥 Test timed out

[lqd]

@bors retry

[bors]

⌛ Testing commit d080532 with merge c2e493e84bd3dbf2f2bab89f23fd40f6520e0d3c...

[bors]

💔 Test failed - checks-actions

[rust-log-analyzer]

The job x86_64-gnu-aux failed! Check out the build log: (web) (plain)

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

error: process exited with code 101 (expected 0)
--- stdout

--- stderr
error: could not execute process `/checkout/obj/build/x86_64-unknown-linux-gnu/stage2-tools/x86_64-unknown-linux-gnu/tmp/cit/t2500/lib/./foo -vV` (never executed)
Caused by:
  Text file busy (os error 26)
', src/tools/cargo/tests/testsuite/workspaces.rs:2176:42

---
test result: FAILED. 2530 passed; 1 failed; 142 ignored; 0 measured; 0 filtered out; finished in 112.03s

error: test failed, to rerun pass `--test testsuite`
Build completed unsuccessfully in 0:26:16
make: *** [Makefile:44: check-aux] Error 1

[cjgillot]

@bors retry

[bors]

⌛ Testing commit d080532 with merge 4c736a2...

[bors]

☀️ Test successful - checks-actions
Approved by: lqd
Pushing 4c736a2 to master...

[rust-timer]

Finished benchmarking commit (4c736a2): comparison URL.

Overall result: ❌ regressions - no action needed

@rustbot label: -perf-regression

Instruction count

This is a highly reliable metric that was used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	1.7%	[1.7%, 1.7%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

Max RSS (memory usage)

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-1.3%	[-1.3%, -1.3%]	1
Improvements ✅ (secondary)	-2.3%	[-2.3%, -2.3%]	1
All ❌✅ (primary)	-1.3%	[-1.3%, -1.3%]	1

Cycles

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	2.7%	[2.7%, 2.7%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0