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Internal llvm failure if using -O2 with thumbv7em-linux-eabi target #14870

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farcaller opened this issue Jun 13, 2014 · 3 comments
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Internal llvm failure if using -O2 with thumbv7em-linux-eabi target #14870

farcaller opened this issue Jun 13, 2014 · 3 comments

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@farcaller
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On cross-compiling libcore, if cpu is locked in to cortex-m4 and -O2 is used, llvm fails with unreachable:

rustc --target thumbv7em-linux-eabi -Ctarget-cpu=cortex-m4 --opt-level 2 libcore/lib.rs
Unexpected member type for HA
UNREACHABLE executed at /Users/farcaller/temp/rust/src/llvm/lib/Target/ARM/ARMCallingConv.h:213!

Compiling without --opt-level 2 or -Ctarget-cpu=cortex-m4 works as expected.

PS: I think this is an LLVM bug, but I cannot figure out a small test case.
@farcaller farcaller mentioned this issue Jun 13, 2014
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@alexcrichton
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This is the IR run through bugpoint: https://gist.github.com/ff0487dadc8576d07bdf.

This isn't very actionable on our end as this definitely looks like an LLVM bug, so I'm going to close this. I would recommend reporting the bugpoint output upstream after trying to minimize it further.

@farcaller
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It seems that this one is actually fixed at r209650 of llvm. What's the rust policy to bump tracking llvm version?

@alexcrichton
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If you make a pull request against rust-lang/llvm with the new commits, I can push so you can update the submodule.

flip1995 pushed a commit to flip1995/rust that referenced this issue May 31, 2025
@Jarcho
Optimize documentation lints **a lot** (2/2) (7.5% -> 1%) (rust-lang#…
1029572 
…14870)

So, after rust-lang/rust-clippy#14693 was
merged,
this is the continuation. It performs some optimizations on
`Fragments::span`
, makes it so we don't call it so much, and makes a 85.75% decrease
(7.51% -> 1.07%)
in execution samples of `source_span_for_markdown_range` and a 6.39% ->
0.88%
for `core::StrSearcher::new`. Overall a 13.11% icount decrase on
docs-heavy crates.

Benchmarked mainly on `regex-1.10.5`.

@rustbot label +performance-project

This means that currently our heaviest function is
`rustc_middle::Interners::intern_ty`, even
for documentation-heavy crates

Along with rust-lang/rust-clippy#14693, this makes the lint a 7% of what
it was before and makes it so that even in the most doc-heavy of crates
it's not an issue.

changelog:Optimize documentation lints by a further 85%

r? @Jarcho
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@farcaller @alexcrichton