Externally implementable items

[jdonszelmann]

Supersedes #140010
Tracking issue: #125418

Getting started:

#![feature(eii)]

#[eii(eii1)]
pub fn decl1(x: u64) 
// body optional (it's the default)
{
    println!("default {x}");
}

// in another crate, maybe
#[eii1]
pub fn decl2(x: u64) {
    println!("explicit {x}");
}

fn main() {
    decl1(4);
}

• tiny perf regression, underlying issue makes multiple things in the compiler slow, not just EII, planning to solve those separately.
• No codegen_gcc support, they don't have bindings for weak symbols yet but could
• No windows support yet for weak definitions

This PR merges the implementation of EII for just llvm + not windows, doesn't yet contain like a new panic handler implementation or alloc handler. With this implementation, it would support implementing the panic handler in terms of EII already since it requires no default implementation so no weak symbols

The PR has been open in various forms for about a year now, but I feel that having some implementation merged to build upon

[jdonszelmann]

@bors2 try @rust-timer queue

[rust-bors]

☀️ Try build successful (CI)
Build commit: d5a6633 (d5a66337e06d3b77a1ab8f6793055535195c3ae9, parent: 364da5d88d772fa40fb20353443595385443ac25)

[rust-timer]

Finished benchmarking commit (d5a6633): comparison URL.

Overall result: ❌ regressions - please read the text below

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.

Next Steps: If you can justify the regressions found in this try perf run, please do so in sufficient writing along with @rustbot label: +perf-regression-triaged. If not, please fix the regressions and do another perf run. If its results are neutral or positive, the label will be automatically removed.

@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)	0.3%	[0.1%, 1.5%]	19
Regressions ❌ (secondary)	0.4%	[0.1%, 1.0%]	44
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.0%	[-0.1%, -0.0%]	4
All ❌✅ (primary)	0.3%	[0.1%, 1.5%]	19

Max RSS (memory usage)

Results (primary 1.7%, secondary 3.9%)

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

	mean	range	count
Regressions ❌ (primary)	1.7%	[0.6%, 2.3%]	6
Regressions ❌ (secondary)	4.7%	[1.1%, 11.2%]	16
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-2.1%	[-2.9%, -1.2%]	2
All ❌✅ (primary)	1.7%	[0.6%, 2.3%]	6

Cycles

Results (primary 3.1%, secondary -1.3%)

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

	mean	range	count
Regressions ❌ (primary)	3.1%	[3.1%, 3.1%]	1
Regressions ❌ (secondary)	3.2%	[2.5%, 3.6%]	3
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-2.8%	[-4.1%, -2.0%]	9
All ❌✅ (primary)	3.1%	[3.1%, 3.1%]	1

Binary size

Results (primary 0.0%, secondary 0.1%)

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

	mean	range	count
Regressions ❌ (primary)	0.0%	[0.0%, 0.1%]	93
Regressions ❌ (secondary)	0.1%	[0.0%, 0.3%]	61
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.0%	[0.0%, 0.1%]	93

Bootstrap: 468.052s -> 471.14s (0.66%)
Artifact size: 387.52 MiB -> 390.25 MiB (0.71%)

[jdonszelmann]

Well, shit. I think I know some fixes but I hoped this wouldn't happen

[bors]

💔 Test failed - checks-actions

[jdonszelmann]

@bors try jobs auto

let's do a full ci build before attempting the merge. I think this is all, just making sure :

[rust-bors]

Unknown argument "jobs:". Run @bors2 help to see available commands.

[jdonszelmann]

@bors try jobs=auto

[jdonszelmann]

ah, there we go...

[jdonszelmann]

nope, still not. well let's at least test mingw

@bors try jobs=x86_64-mingw-1

[rust-bors]

☀️ Try build successful (CI)
Build commit: ac3a540 (ac3a540eefa022a9ca61a06b34b6511a694457c8, parent: eb171a227f9e5de5d376b6edb56b174bc8235fb3)

[jdonszelmann]

Well, fixed mingw, just a warning remaining...

[jdonszelmann]

ah forgot to bless a test

[jdonszelmann]

@rustbot review
let's try once more... nothing really changed except that I now explicitly exclude windows targets. I knew windows didn't work, but somehow I never actually remembered to exclude windows from running tests...

windows now passes (see try build). I guess it's time for another attempt at big ci

[jdonszelmann]

@bors r=lcnr,oli-obk

[bors]

📌 Commit 065e4c1 has been approved by lcnr,oli-obk

It is now in the queue for this repository.

[bors]

⌛ Testing commit 065e4c1 with merge 3f4dc1e...