Only compute vtable information during codegen

[compiler-errors]

This PR removes vtable information from the Object and TraitUpcasting candidate sources in the trait solvers, and defers the computation of relevant information to Instance::resolve. This is because vtables really aren't a thing in the trait world -- they're an implementation detail in codegen.

Previously it was just easiest to tangle this information together since we were already doing the work of looking at all the supertraits in the trait solver, and specifically because we use traits to represent when it's possible to call a method via a vtable (Object candidate) and do upcasting (Unsize candidate). but I am somewhat suspicious we're doing a lot of extra work, especially in polymorphic contexts, so let's see what perf says.

[rustbot]

Some changes occurred to the core trait solver

cc @rust-lang/initiative-trait-system-refactor

Some changes occurred in compiler/rustc_codegen_cranelift

cc @bjorn3

[compiler-errors]

@bors try @rust-timer queue

[bors]

⌛ Trying commit 343e079 with merge 19ca3c6...

[bors]

☀️ Try build successful - checks-actions
Build commit: 19ca3c6 (19ca3c6af7d6d1786b7aea51899fed72fcf48b6a)

[compiler-errors]

@bors try @rust-timer queue

[bors]

⌛ Trying commit 3b9adbe with merge ad3edf4...

[bors]

☀️ Try build successful - checks-actions
Build commit: ad3edf4 (ad3edf4cdc6b8cfa2e6e2e609234936e5b39bcaf)

[rust-timer]

Finished benchmarking commit (ad3edf4): 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 3.4%)

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)	3.4%	[3.4%, 3.4%]	1
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	3.4%	[3.4%, 3.4%]	1

Cycles

Results (secondary 3.8%)

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)	3.8%	[3.8%, 3.8%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

Binary size

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

Bootstrap: 671.602s -> 672.019s (0.06%)
Artifact size: 320.43 MiB -> 319.77 MiB (-0.21%)

[compiler-errors]

Ok perfect. Even if this isn't a major perf improvement, I'd still like to do this since it removes a dependency on vtable information from the new trait solver.

r? compiler

[lcnr]

@bors r+ rollup=never

[bors]

📌 Commit 3b9adbe has been approved by lcnr

It is now in the queue for this repository.

[bors]

⌛ Testing commit 3b9adbe with merge 5639c21...

[bors]

☀️ Test successful - checks-actions
Approved by: lcnr
Pushing 5639c21 to master...

[rust-timer]

Finished benchmarking commit (5639c21): comparison URL.

Overall result: ❌✅ regressions and 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)	0.3%	[0.3%, 0.3%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.2%	[-0.2%, -0.2%]	1
All ❌✅ (primary)	-	-	0

Max RSS (memory usage)

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

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: 671.288s -> 671.71s (0.06%)
Artifact size: 320.38 MiB -> 320.54 MiB (0.05%)