Drop array patterns using subslices

[clubby789]

Fixes #109004
Drops contiguous subslices of an array when moving elements out with a pattern, which improves perf for large arrays
r? @compiler-errors

[compiler-errors]

@bors try @rust-timer queue

[bors]

⌛ Trying commit fb7275c5f1fd470a7bb97cbac0a71224b280fad7 with merge f6318045f80c3b6b7cee0b1c420dd1a84ce61091...

[compiler-errors]

Also this will eventually need a UI test :)

[bors]

💔 Test failed - checks-actions

[compiler-errors]

@bors try @rust-timer queue

[bors]

⌛ Trying commit f9e457ff59cdd3daef958fcac7e0dfefb3eb3051 with merge 8633c7b8d24f7723cc99e11b7a9707871935a2b6...

[bors]

☀️ Try build successful - checks-actions
Build commit: 8633c7b8d24f7723cc99e11b7a9707871935a2b6 (8633c7b8d24f7723cc99e11b7a9707871935a2b6)

[rust-timer]

Finished benchmarking commit (8633c7b8d24f7723cc99e11b7a9707871935a2b6): 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 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
Improvements ✅ (primary)	-0.4%	[-0.4%, -0.4%]	2
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-0.4%	[-0.4%, -0.4%]	2

Max RSS (memory usage)

Results

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)	-	-	0
Improvements ✅ (secondary)	-1.0%	[-1.2%, -0.9%]	2
All ❌✅ (primary)	-	-	0

Cycles

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

[clubby789]

This now fixes the case from the example, but still blows up memory when the huge array is partially moved from.

[compiler-errors]

I'm happy to r+ this with a detailed comment, both explaining what the double iteration is doing and where it falls short, and a UI test.

[clubby789]

Added a test and explanation, but I'll try and investigate a better solution for this

[clubby789]

Found a new approach that seems to work, passing relevant drop tests locally and fixes both dropping large arrays and moving out of them.

1. Iterate over array_subpath for each index, recording contiguous ranges where array_subpath is None
2. For any indexes which are Some, push the current range, then path and then start a new range
3. Iterate backward over the ranges - for a Drop, make a place for the subslice and for a Keep make a place for the index
4. Pass these places and paths to the drop ladder as before

I'll squash + update PR desc if this looks good

@rustbot ready

[bors]

📌 Commit ce2d528 has been approved by davidtwco

It is now in the queue for this repository.

[bors]

⌛ Testing commit ce2d528 with merge f71b58d5b418fbf1b5156d833b464bb60470d38b...

[rust-log-analyzer]

The job mingw-check failed! Check out the build log: (web) (plain)

Click to see the possible cause of the failure (guessed by this bot)

    Finished release [optimized] target(s) in 12.39s
[TIMING] check::CodegenBackend { target: i686-pc-windows-gnu, backend: "cranelift" } -- 12.403
Checking stage0 gcc library (x86_64-unknown-linux-gnu -> i686-pc-windows-gnu)
    Updating git repository `https://github.com/antoyo/gccjit.rs`
warning: spurious network error (2 tries remaining): failed to connect to github.com: Connection refused; class=Os (2)
warning: spurious network error (1 tries remaining): failed to connect to github.com: Connection refused; class=Os (2)
error: failed to get `gccjit` as a dependency of package `rustc_codegen_gcc v0.1.0 (/checkout/compiler/rustc_codegen_gcc)`
Caused by:
Caused by:
  failed to load source for dependency `gccjit`
Caused by:
  Unable to update https://github.com/antoyo/gccjit.rs#fe242b7e

Caused by:
Caused by:
  failed to clone into: /cargo/git/db/gccjit.rs-13c2e290f2fb9e4d
Caused by:
  failed to connect to github.com: Connection refused; class=Os (2)
Build completed unsuccessfully in 0:01:39

[bors]

💔 Test failed - checks-actions

[cjgillot]

@bors retry failed to connect to github.com

[bors]

⌛ Testing commit ce2d528 with merge 9482c66f424c8c22af3c6dab3afa7af5fd870e44...

[rust-log-analyzer]

A job failed! Check out the build log: (web) (plain)

Click to see the possible cause of the failure (guessed by this bot)

[bors]

💔 Test failed - checks-actions

[cjgillot]

@bors retry failed during checkout

[bors]

⌛ Testing commit ce2d528 with merge a5a690c...

[bors]

☀️ Test successful - checks-actions
Approved by: davidtwco
Pushing a5a690c to master...

[bors]

☀️ Test successful - checks-actions
Approved by: davidtwco
Pushing a5a690c to master...

[rust-timer]

Finished benchmarking commit (a5a690c): comparison URL.

Overall result: ✅ 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
Improvements ✅ (primary)	-0.4%	[-0.4%, -0.4%]	2
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-0.4%	[-0.4%, -0.4%]	2

Max RSS (memory usage)

Results

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)	-	-	0
Improvements ✅ (secondary)	-2.5%	[-2.5%, -2.4%]	2
All ❌✅ (primary)	-	-	0

Cycles

Results

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