allow LTO on proc-macro crates with -Zdylib-lto

[onur-ozkan]

ref #115986 (comment)

Fixes #110296

[rustbot]

r? @Mark-Simulacrum

(rustbot has picked a reviewer for you, use r? to override)

[bjorn3]

We do that as Cargo ignores the LTO setting for dylibs, despite our use of -Zdylib-lto to allow this. We could make -Zdylib-lto work for proc-macros too I think by allowing ProcMacro in crate_type_allows_lto. (And adding ProcMacro to the else if at

rust/compiler/rustc_codegen_llvm/src/back/lto.rs

Line 85 in 0e11725

} else if *crate_type == CrateType::Dylib {

to ensure it only works behind -Zdylib-lto)

[onur-ozkan]

@rustbot author

[onur-ozkan]

@rustbot ready

[onur-ozkan]

r? wesleywiser

[wesleywiser]

@bors r+

[bors]

📌 Commit bdd66b3 has been approved by wesleywiser

It is now in the queue for this repository.

[bors]

⌛ Testing commit bdd66b3 with merge a327e75...

[bors]

☀️ Test successful - checks-actions
Approved by: wesleywiser
Pushing a327e75 to master...

[rust-timer]

Finished benchmarking commit (a327e75): comparison URL.

Overall result: no relevant changes - no action needed

@rustbot label: -perf-regression

Instruction count

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

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)	2.3%	[2.3%, 2.3%]	1
Regressions ❌ (secondary)	2.9%	[2.6%, 3.1%]	2
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-1.0%	[-1.5%, -0.7%]	5
All ❌✅ (primary)	2.3%	[2.3%, 2.3%]	1

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: 630.048s -> 631.465s (0.22%)
Artifact size: 317.24 MiB -> 317.37 MiB (0.04%)