Use fewer intermediate functions for short backtraces in queries

[Zalathar]

If we make sure that compute_fn in the query's vtable is actually named __rust_begin_short_backtrace, we can avoid the need for some additional intermediate functions and stack frames.

This is similar to how the get_query_incr and get_query_non_incr functions are actually named __rust_end_short_backtrace.

---

• Earlier draft of this PR: [EXPERIMENT] Reduce short-backtrace overhead in some query plumbing call stacks #151719
• Introduction of this backtrace-trimming: Shorten backtraces for queries in ICEs #108938

[rustbot]

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[Zalathar]

Let's have another perf run for the non-draft PR:

@bors try @rust-timer queue

[rust-bors]

☀️ Try build successful (CI)
Build commit: 21dc8d7 (21dc8d7b26dfebb8e4647a138974547b9b201161, parent: 78df2f92de1da3601d967dc8beb9f9cea267e45f)

[rust-timer]

Finished benchmarking commit (21dc8d7): comparison URL.

Overall result: ❌✅ regressions and improvements - no action needed

Benchmarking this pull request means it may be perf-sensitive – we'll automatically label it not fit for rolling up. You can override this, but we strongly advise not to, due to possible changes in compiler perf.

@bors rollup=never
@rustbot label: -S-waiting-on-perf -perf-regression

Instruction count

Our most reliable metric. Used to determine the overall result above. However, even this metric can be noisy.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	0.0%	[0.0%, 0.1%]	3
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.1%	[-0.2%, -0.0%]	4
All ❌✅ (primary)	-	-	0

Max RSS (memory usage)

Results (primary -1.6%, secondary -2.2%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-1.6%	[-1.9%, -1.3%]	2
Improvements ✅ (secondary)	-2.2%	[-3.3%, -1.7%]	3
All ❌✅ (primary)	-1.6%	[-1.9%, -1.3%]	2

Cycles

Results (secondary 1.2%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	4.7%	[2.7%, 6.4%]	4
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-3.6%	[-3.8%, -3.4%]	3
All ❌✅ (primary)	-	-	0

Binary size

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

Bootstrap: 472.873s -> 474.195s (0.28%)
Artifact size: 385.68 MiB -> 383.56 MiB (-0.55%)