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non-nightly rustc reports opt-level s and z are possible options #47651

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mrhota opened this issue Jan 22, 2018 · 0 comments · Fixed by #50265
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non-nightly rustc reports opt-level s and z are possible options #47651

mrhota opened this issue Jan 22, 2018 · 0 comments · Fixed by #50265
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C-enhancement Category: An issue proposing an enhancement or a PR with one.

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@mrhota
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mrhota commented Jan 22, 2018

The code around opt-levels indicates only nightly rustc can use opt-level=s or opt-level=z. Non-nightly rustcs should not even report those values as possible options.
@mrhota mrhota mentioned this issue Jan 22, 2018
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@Mark-Simulacrum Mark-Simulacrum added the C-enhancement Category: An issue proposing an enhancement or a PR with one. label Jan 22, 2018
@varkor varkor mentioned this issue Apr 27, 2018
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bors added a commit that referenced this issue May 21, 2018
@bors
Auto merge of #50265 - japaric:sz, r=alexcrichton
6e6a4b1 
stabilize opt-level={s,z}

closes #35784
closes #47651

### Rationale

Since the lastest LLVM upgrade rustc / LLVM does more agressive loop unrolling. This results in increased binary size of embedded / no_std programs: a hundreds of bytes increase, or about a 7x increase, in the case of the smallest Cortex-M binary cf. #49260.

As we are shooting for embedded Rust on stable it would be great to also provide a way to optimize for size (which is pretty important for embedded applications that target resource constrained devices) on stable.

Also this has been baking in nightly for a long time.

r? @alexcrichton which team has to sign off this?
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stabilize opt-level={s,z} japaric/rust
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