Stop walking the bodies of statics for reachability, and evaluate them instead

[oli-obk]

cc @saethlin @RalfJung

cc #119214

This reuses the DefIdVisitor from rustc_privacy, because they basically try to do the same thing.

This PR's changes can probably be extended to constants, too, but let's tackle that separately, it's likely more involved.

[rustbot]

r? @fee1-dead

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[oli-obk]

@bors try @rust-timer queue

[rustbot]

These commits modify the Cargo.lock file. Unintentional changes to Cargo.lock can be introduced when switching branches and rebasing PRs.

If this was unintentional then you should revert the changes before this PR is merged.
Otherwise, you can ignore this comment.

[bors]

⌛ Trying commit 7b7b6b5 with merge 1a609b9...

[fee1-dead]

Not familiar with this code, sorry.

r? compiler

[RalfJung]

I can't really comment on this PR, as I know neither the intended semantics of this "reachable" pass nor the way it is used.

It would be good to have some place that documents the intended semantics -- does that exist currently? Does it need updating with this PR?

[bors]

☀️ Try build successful - checks-actions
Build commit: 1a609b9 (1a609b9da1e44fc0d4e3b1a85563596147865afb)

[saethlin]

I'm pretty sure fmease doesn't know this part of the compiler either. I'll take a careful look over this later, but I think @tmiasko is a good reviewer for this based on past conversations.

r? tmiasko

[rust-timer]

Finished benchmarking commit (1a609b9): comparison URL.

Overall result: ✅ 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-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.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-1.3%	[-1.4%, -1.2%]	2
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)	7.0%	[7.0%, 7.0%]	1
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-1.0%	[-1.0%, -1.0%]	1
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	3.0%	[-1.0%, 7.0%]	2

Cycles

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

Binary size

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)	0.0%	[0.0%, 0.0%]	1
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-0.1%	[-0.1%, -0.1%]	6
Improvements ✅ (secondary)	-0.7%	[-3.7%, -0.0%]	6
All ❌✅ (primary)	-0.1%	[-0.1%, 0.0%]	7

Bootstrap: 670.966s -> 671.851s (0.13%)
Artifact size: 310.09 MiB -> 310.02 MiB (-0.02%)

[tmiasko]

Could you also add a negative test case demonstrating that calling a function from an initializer of a reachable static no longer makes the function reachable?

[oli-obk]

Added a test, and showed how it changes in the second commit

[tmiasko]

@bors r+

[bors]

📌 Commit 746e4ef has been approved by tmiasko

It is now in the queue for this repository.

[bors]

⌛ Testing commit 746e4ef with merge c563f2e...

[bors]

☀️ Test successful - checks-actions
Approved by: tmiasko
Pushing c563f2e to master...

[rust-timer]

Finished benchmarking commit (c563f2e): comparison URL.

Overall result: ✅ improvements - 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)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-1.0%	[-1.4%, -0.2%]	3
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)	2.6%	[2.6%, 2.6%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

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)	0.9%	[0.9%, 0.9%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

Binary size

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)	-0.0%	[-0.1%, -0.0%]	6
Improvements ✅ (secondary)	-0.7%	[-3.7%, -0.0%]	6
All ❌✅ (primary)	-0.0%	[-0.1%, -0.0%]	6

Bootstrap: 670.952s -> 670.527s (-0.06%)
Artifact size: 311.63 MiB -> 311.59 MiB (-0.01%)