Describe lifetime of call argument temporaries passed indirectly

[tmiasko]

Fixes #132014.

[rustbot]

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[rustbot]

Some changes occurred in compiler/rustc_codegen_ssa

cc @WaffleLapkin

[tmiasko]

r? codegen

[workingjubilee]

typo, also slightly confusing wording to me, and often comments like this are written in the imperative, so perhaps this could be more like

Suggested change

	// Keeps track of temporary allocas whose liftime need to be ended after the call.
	// Keep track of temporary allocas with lifetimes that end after this call

[workingjubilee]

The exact phrasing isn't too important tho' and I don't necessarily insist on the imperative, please feel free to revise as you see fit.

[workingjubilee]

also comments should generally prefer to include "why": probably this?

Suggested change

	let mut lifetime_ends_after_call: Vec<(Bx::Value, Size)> = Vec::new();
	// because we want to later emit things like `@llvm.lifetime.end` for them.
	let mut lifetime_ends_after_call: Vec<(Bx::Value, Size)> = Vec::new();

[workingjubilee]

Also one thing we kinda lose here with this rename is that most of the entities in this list are arguments or owned by the effective arguments: that's why we accumulate them through codegen_argument calls, then actually handle emitting llvm.lifetime.end intrinsics and the like in do_call. Without this explicitly being called out in the identifier's name, you have to then go read another few hundred lines of code to extract that. We could probably spare a line of commentary here on that subject.

[workingjubilee]

I wonder
@bors try @rust-timer queue

[bors]

⌛ Trying commit 653bbb9 with merge 9f0b7ad...

[bors]

☀️ Try build successful - checks-actions
Build commit: 9f0b7ad (9f0b7ad5494592153b6b7b686a00930bd3b8cf6d)

[rust-timer]

Finished benchmarking commit (9f0b7ad): 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)

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

Cycles

Results (primary 1.8%)

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)	1.8%	[1.8%, 1.8%]	1
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	1.8%	[1.8%, 1.8%]	1

Binary size

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

Bootstrap: missing data
Artifact size: 365.54 MiB -> 365.55 MiB (0.00%)

[workingjubilee]

Cool. I was just checking for regressions in other cases.