linker: Report linker flavors incompatible with the current target

[petrochenkov]

The linker flavor is checked for target compatibility even if linker is never used (e.g. we are producing a rlib).
If it causes trouble, we can move the check to link.rs so it will run if the linker (flavor) is actually used.

And also feature gate explicitly specifying linker flavors for tier 3 targets.

The next step is supporting all the internal linker flavors in user-visible interfaces (command line and json).

[rustbot]

r? @b-naber

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[rustbot]

These commits modify compiler targets.
(See the Target Tier Policy.)

[b-naber]

r? rust-lang/compiler

[petrochenkov]

cc @lqd

[lqd]

The linker flavor is checked for target compatibility even if linker is never used (e.g. we are producing a rlib)

That seems fine under "common usage" and targets, right (even in cross- compilation cases) ?

Maybe we can do a perf run just to exercize the PR with a few real world crates with build scripts and proc-macros, in case rustc-perf has more coverage there than our tests in practice. (I wouldn’t really expect issues to be found per se)

Did we ever consider the bpf/ptx linker flavors stable ?

Otherwise this LGTM.

[petrochenkov]

@lqd

That seems fine under "common usage" and targets, right (even in cross- compilation cases) ?

Yes, the only cases of breakage I can imagine are 1) wrong -Clinker-flavor is added accidentally and never used because no linking happens and 2) compile-fail tests in our own test suite.

Maybe we can do a perf run just to exercize the PR with a few real world crates with build scripts and proc-macros, in case rustc-perf has more coverage there than our tests in practice. (I wouldn’t really expect issues to be found per se)

I wouldn't expect any effect on performance, this is a cheap check that is performed once during compilation.

Did we ever consider the bpf/ptx linker flavors stable ?

I guess no?
But technically they could be specified with a stable compiler and non tier-3 targets in cases when no linking actually happens (e.g. producing a rlib).
But I wouldn't expect it to ever happen in practice, these are the only working linker flavors for bpf/ptx targets respectively, you never need to specify them explicitly.

[petrochenkov]

This needs a couple of tests, one for the target compat check and another for the feature gates.

[petrochenkov]

Added tests.
@rustbot ready

[wesleywiser]

I don't think it matters but nvptx64-nvidia-cuda is Tier 2, not Tier 3.

[wesleywiser]

@bors r=lqd,wesleywiser

[bors]

📌 Commit 6675f46389bc931c0d73da75ed709846e2f76c53 has been approved by lqd,wesleywiser

It is now in the queue for this repository.

[bors]

⌛ Testing commit 6675f46389bc931c0d73da75ed709846e2f76c53 with merge f74e273755395be9266f36badf49b933af48b1ed...

[petrochenkov]

@bors r=lqd,wesleywiser

[bors]

📌 Commit 2f7328d has been approved by lqd,wesleywiser

It is now in the queue for this repository.

[Nilstrieb]

looks like this broke dist-x86_64-linux? #112092 (comment)
@bors r-

[Nilstrieb]

Nevermind, it was innocent: #112095 (comment)

@bors r=lqd,wesleywiser

[bors]

📌 Commit 2f7328d has been approved by lqd,wesleywiser

It is now in the queue for this repository.

[bors]

⌛ Testing commit 2f7328d with merge 9af3865...

[bors]

☀️ Test successful - checks-actions
Approved by: lqd,wesleywiser
Pushing 9af3865 to master...

[rust-timer]

Finished benchmarking commit (9af3865): comparison URL.

Overall result: ❌ regressions - 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)	0.6%	[0.6%, 0.6%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

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)	2.3%	[2.3%, 2.3%]	2
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

Cycles

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

Binary size

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

Bootstrap: 643.718s -> 644.991s (0.20%)