Folder experiment: Account for type flags in fold_predicate in Canonicalizer

[compiler-errors]

NOTE: This is one of a series of perf experiments that I've come up with while sick in bed. I'm assigning them to lqd b/c you're a good reviewer and you'll hopefully be awake when these experiments finish, lol.

r? lqd

The canonicalizer is used a lot in borrowck and in the eval-flavor of the trait solver. Let's avoid doing unnecessary work when folding predicates, which I would assume are a very important input to the canonicalizer as the main "type" of all goals and such.

[compiler-errors]

Ok this is the last one.

@bors try @rust-timer queue

[bors]

⌛ Trying commit 7d2c08f with merge 1dc5c24...

[bors]

☀️ Try build successful - checks-actions
Build commit: 1dc5c24 (1dc5c24334b79a1ee3da56390616d5c2c55c119f)

[rust-timer]

Finished benchmarking commit (1dc5c24): 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 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
Improvements ✅ (primary)	-0.3%	[-0.3%, -0.3%]	2
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-0.3%	[-0.3%, -0.3%]	2

Max RSS (memory usage)

Results (primary 1.4%, secondary -1.3%)

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)	1.4%	[0.9%, 2.1%]	3
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-1.3%	[-1.3%, -1.3%]	1
All ❌✅ (primary)	1.4%	[0.9%, 2.1%]	3

Cycles

Results (secondary 3.0%)

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)	3.0%	[3.0%, 3.0%]	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: 777.539s -> 775.128s (-0.31%)
Artifact size: 365.91 MiB -> 365.95 MiB (0.01%)

[compiler-errors]

Minor improvements at best, probably noise.