Foundations of location-sensitive polonius

[lqd]

I'd like to land the prototype I'm describing in the polonius project goal. It still is incomplete and naive and terrible but it's working "well enough" to consider landing.

I'd also like to make review easier by not opening a huge PR, but have a couple small-ish ones (the +/- line change summary of this PR looks big, but >80% is moving datalog to a single place).

This PR starts laying the foundation for that work:

• it refactors and collects 99% of the old datalog fact gen, which was spread around everywhere, into a single dedicated module. It's still present at 3 small places (one of which we should revert anyways) that are kinda deep within localized components and are not as easily extractable into the rest of fact gen, so it's fine for now.
• starts introducing the localized constraints, the building blocks of the naive way of implementing the location-sensitive analysis in-tree, which is roughly sketched out in https://smallcultfollowing.com/babysteps/blog/2023/09/22/polonius-part-1/ and https://smallcultfollowing.com/babysteps/blog/2023/09/29/polonius-part-2/ but with a different vibe than per-point environments described in these posts, just r1@p: r2@q constraints.
• sets up the skeleton of generating these localized constraints: converting NLL typeck constraints, and creating liveness constraints
• introduces the polonius dual to NLL MIR to help development and debugging. It doesn't do much currently but is a way to see these localized constraints: it's an NLL MIR dump + a dumb listing of the constraints, that can be dumped with -Zdump-mir=polonius -Zpolonius=next. Its current state is not intended to be a long-term thing, just for testing purposes -- I will replace its contents in the future with a different approach (an HTML+js file where we can more easily explore/filter/trace these constraints and loan reachability, have mermaid graphs of the usual graphviz dumps, etc).

I've started documenting the approach in this PR, I'll add more in the future. It's quite simple, and should be very clear when more constraints are introduced anyways.

r? @matthewjasper

Best reviewed per commit so that the datalog move is less bothersome to read, but if you'd prefer we separate that into a different PR, I can do that (and michael has offered to review these more mechanical changes if it'd help).

[lqd]

This should all be gated away and deactivatd by default, but let's check: @bors try @rust-timer queue

[bors]

⌛ Trying commit 1331ccb with merge 0b8e535...

[bors]

☀️ Try build successful - checks-actions
Build commit: 0b8e535 (0b8e535a30719ca2ebdd3c9ebb1ea3f99530bd26)

[rust-timer]

Finished benchmarking commit (0b8e535): comparison URL.

Overall result: no relevant changes - 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 benchmark run did not return any relevant results for this metric.

Max RSS (memory usage)

Results (primary 4.6%, secondary 2.7%)

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)	4.6%	[4.6%, 4.6%]	1
Regressions ❌ (secondary)	2.7%	[2.7%, 2.7%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	4.6%	[4.6%, 4.6%]	1

Cycles

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

Binary size

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

Bootstrap: 770.238s -> 768.851s (-0.18%)
Artifact size: 330.40 MiB -> 330.38 MiB (-0.00%)

[jackh726]

Started the review this, but need to step away. Thoughts:

First, do you have a branch with all the changes you've made so far? Could be good to link it if so for context.

Second, this is still a "big" PR, definitely worth splitting into a couple, I think.

That being said, reviewed the first 2 commits and r+ for me on them (if you want to split them out). I'll keep going through the commits as I get time.

[lqd]

First, do you have a branch with all the changes you've made so far? Could be good to link it if so for context.

Yes and no, I have a messy older incomplete one and a bunch of local changes because I'm still working on it, so I'm basically cleaning them up as I go to open PRs.

Second, this is still a "big" PR, definitely worth splitting into a couple, I think.

Ok. I'll split the first 2 commits out now, it should simplify this PR a bit. I can split the rest of the old polonius' fact gen later if you or michael want to look at it.

(I also rebased to fix conflicts)

[jackh726]

Have reviewed first 8 commits (through "improve consistency..."). A small nit, but otherwise r=me if you want to split them out.

[jackh726]

Cursory review of commits 9 onward.

Overall they look fine, but didn't think too deeply so not a full approval.

[jackh726]

I will come back to this for approval of the last few commits once the PR with the first 8 commits lands.

[lqd]

I rebased after #134378 landed.

[jackh726]

r? jackh726

@bors r+

[bors]

📌 Commit aeb3d10 has been approved by jackh726

It is now in the queue for this repository.

[bors]

⌛ Testing commit aeb3d10 with merge 426d173...

[bors]

☀️ Test successful - checks-actions
Approved by: jackh726
Pushing 426d173 to master...

[rust-timer]

Finished benchmarking commit (426d173): comparison URL.

Overall result: ❌ regressions - no action needed

@rustbot label: -perf-regression

Instruction count

This is the most reliable metric that we have; it was used to determine the overall result at the top of this comment. However, even this metric can sometimes exhibit noise.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	0.2%	[0.2%, 0.2%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

Max RSS (memory usage)

Results (primary 2.2%)

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)	2.2%	[2.2%, 2.2%]	1
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	2.2%	[2.2%, 2.2%]	1

Cycles

Results (primary -4.4%)

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)	-4.4%	[-6.7%, -2.0%]	2
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-4.4%	[-6.7%, -2.0%]	2

Binary size

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

Bootstrap: 760.428s -> 762.028s (0.21%)
Artifact size: 330.62 MiB -> 330.62 MiB (0.00%)