ci: docker: dist-various-1: Include RISC-V C compilers

[alistair23]

The compiler-builtins for RISC-V are missing some key functions, such as __bswapsi2 [1].

We can't just pull in the LLVM compiler-rt builtins as the rust-lang/rust distribution container doesn't have a C compiler [2].

This patch adds RISC-V C compilers to the CI Dockerfile as the first step towards enabling LLVM compiler-rt builtins for RISC-V Rust.

1: rust-lang/compiler-builtins#350
2: rust-lang/compiler-builtins@e4f46b9

[rustbot]

r? @Kobzol

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[Kobzol]

The actual CI changes look fine to me, but I don't really know anything about RISC-V and Rust's setup of it, so also CCing @Mark-Simulacrum.

[nikic]

Shouldn't implementation for these be added to compiler-builtins instead?

[alistair23]

Shouldn't implementation for these be added to compiler-builtins instead?

From what I can tell it is a chicken and egg problem. I can't add these to compiler-builtins as there is no toolchain available. So step 1 is to slowly add RISC-V toolchains, so then I can support this in compiler-builtins

[nikic]

Shouldn't implementation for these be added to compiler-builtins instead?

From what I can tell it is a chicken and egg problem. I can't add these to compiler-builtins as there is no toolchain available. So step 1 is to slowly add RISC-V toolchains, so then I can support this in compiler-builtins

By adding to compiler-builtins I meant implementing them inside compiler-builtins using rust code, not pulling them C implementation from compiler-rt in. But seeing the symbol list in rust-lang/compiler-builtins#350 (comment) I guess that's not feasible. I initially thought this is only about trivial things like __bswapsi2 only, but it seems to also affect float builtins.

[alistair23]

By adding to compiler-builtins I meant implementing them inside compiler-builtins using rust code, not pulling them C implementation from compiler-rt in. But seeing the symbol list in rust-lang/compiler-builtins#350 (comment) I guess that's not feasible. I initially thought this is only about trivial things like __bswapsi2 only, but it seems to also affect float builtins.

Ah. Yeah, I there are still a lot missing, which is why the other targets all pull in the LLVM compiler-rt builtins

[alistair23]

Any more comments?

[Kobzol]

I'm sorry, I should have rerolled sooner, I'd like to hear Mark's opinion (as I said, I'm not familiar with this).

r? @Mark-Simulacrum

[Mark-Simulacrum]

@bors r+ rollup=iffy

[bors]

📌 Commit d66a964 has been approved by Mark-Simulacrum

It is now in the queue for this repository.

[bors]

⌛ Testing commit d66a964 with merge b37d43e...

[bors]

☀️ Test successful - checks-actions
Approved by: Mark-Simulacrum
Pushing b37d43e to master...

[rust-timer]

Finished benchmarking commit (b37d43e): 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)	0.3%	[0.3%, 0.3%]	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)	1.3%	[0.6%, 1.9%]	2
Regressions ❌ (secondary)	4.1%	[4.1%, 4.1%]	1
Improvements ✅ (primary)	-1.5%	[-3.5%, -0.5%]	3
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-0.4%	[-3.5%, 1.9%]	5

Cycles

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

Binary size

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)	0.4%	[0.4%, 0.4%]	1
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.4%	[0.4%, 0.4%]	1

Bootstrap: 672.871s -> 671.959s (-0.14%)
Artifact size: 312.47 MiB -> 312.44 MiB (-0.01%)