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jbeich opened this issue Dec 5, 2018 · 3 comments · Fixed by #72094
Closed

-C target-feature=+foo overrides previous values #56527

jbeich opened this issue Dec 5, 2018 · 3 comments · Fixed by #72094
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A-driver Area: rustc_driver that ties everything together into the `rustc` compiler

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@jbeich
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jbeich commented Dec 5, 2018

I'm trying to pass multiple -C target-feature conditionally downstream. However, despite +/- for adding/removing a feature it appears only the last value takes effect.

$ cat >a.rs
fn main() {
    if cfg!(target_feature="avx2") {
        println!("AVX2 available");
    }
    if cfg!(target_feature="fma") {
        println!("FMA available");
    }
}

$ rustc a.rs -C target-feature=+avx2 -C target-feature=+fma
$ ./a
FMA available
$ rustc a.rs -C target-feature=+avx2,+fma
$ ./a
AVX2 available
FMA available
uqs pushed a commit to freebsd/freebsd-ports that referenced this issue Dec 5, 2018
textproc/ripgrep: unbreak AVX=on on i386 after r454995
6ac52d2 
error[E0432]: unresolved import `simd::x86::avx`
  --> cargo-crates/bytecount-0.3.2/src/lib.rs:49:16
   |
49 | use simd::x86::avx::{LowHigh128, u8x32};
   |                ^^^ could not find `avx` in `x86`

rust-lang/rust#56527


git-svn-id: svn+ssh://svn.freebsd.org/ports/head@486650 35697150-7ecd-e111-bb59-0022644237b5
uqs pushed a commit to freebsd/freebsd-ports that referenced this issue Dec 5, 2018
@jbeich
MFH: r486650
8eb9301 
textproc/ripgrep: unbreak AVX=on on i386 after r454995

error[E0432]: unresolved import `simd::x86::avx`
  --> cargo-crates/bytecount-0.3.2/src/lib.rs:49:16
   |
49 | use simd::x86::avx::{LowHigh128, u8x32};
   |                ^^^ could not find `avx` in `x86`

rust-lang/rust#56527

Approved by:	ports-secteam blanket
uqs pushed a commit to freebsd/freebsd-ports that referenced this issue Dec 5, 2018
@jbeich
textproc/ripgrep: unbreak AVX=on on i386 after r454995
4199dc5 
error[E0432]: unresolved import `simd::x86::avx`
  --> cargo-crates/bytecount-0.3.2/src/lib.rs:49:16
   |
49 | use simd::x86::avx::{LowHigh128, u8x32};
   |                ^^^ could not find `avx` in `x86`

rust-lang/rust#56527
swills pushed a commit to swills/freebsd-ports that referenced this issue Dec 5, 2018
@jbeich
textproc/ripgrep: unbreak AVX=on on i386 after r454995
f82ce52 
error[E0432]: unresolved import `simd::x86::avx`
  --> cargo-crates/bytecount-0.3.2/src/lib.rs:49:16
   |
49 | use simd::x86::avx::{LowHigh128, u8x32};
   |                ^^^ could not find `avx` in `x86`

rust-lang/rust#56527


git-svn-id: svn+ssh://svn.freebsd.org/ports/head@486650 35697150-7ecd-e111-bb59-0022644237b5
Jehops pushed a commit to Jehops/freebsd-ports-legacy that referenced this issue Dec 5, 2018
@jbeich
textproc/ripgrep: unbreak AVX=on on i386 after r454995
f54f43d 
error[E0432]: unresolved import `simd::x86::avx`
  --> cargo-crates/bytecount-0.3.2/src/lib.rs:49:16
   |
49 | use simd::x86::avx::{LowHigh128, u8x32};
   |                ^^^ could not find `avx` in `x86`

rust-lang/rust#56527


git-svn-id: svn+ssh://svn.freebsd.org/ports/head@486650 35697150-7ecd-e111-bb59-0022644237b5
@cuviper
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cuviper commented Dec 7, 2018

FWIW, you can check for cfg values without any test program like:

$ rustc --print cfg  -C target-feature=+avx2 -C target-feature=+fma

$ rustc --print cfg  -C target-feature=+avx2,+fma

@jonas-schievink jonas-schievink added the A-driver Area: rustc_driver that ties everything together into the `rustc` compiler label Jan 27, 2019
@petrochenkov
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I agree that it's a bug and will try to fix it.

@petrochenkov petrochenkov self-assigned this May 9, 2020
@petrochenkov petrochenkov mentioned this issue May 10, 2020
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@petrochenkov
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Fixed in #72094.

@petrochenkov petrochenkov removed their assignment May 12, 2020
RalfJung added a commit to RalfJung/rust that referenced this issue May 15, 2020
@RalfJung
Rollup merge of rust-lang#72094 - petrochenkov:overfeature, r=nikic

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7dc2c01 
cmdline: Make target features individually overridable

Fixes rust-lang#56527

Previously `-C target-feature=+avx2 -C target-feature=+fma` was equivalent to `-C target-feature=+fma` because the later `-C target-feature` option fully overridden previous `-C target-feature`.
With this PR `-C target-feature=+avx2 -C target-feature=+fma` is equivalent to `-C target-feature=+avx2,+fma` and the options are combined.

I'm not sure where the comma-separated features in a single option came from (clang uses a scheme with single feature per-option), but logically these features are entirely independent options.
So they should be overridable individually as well to be more useful in hierarchical build system, and more consistent with other rustc options and clang behavior as well.

Target feature options have a few other issues (rust-lang#44815), but fixing those is going to be a bit more invasive.
@bors bors closed this as completed in 4fe6d52 May 16, 2020
@petrochenkov petrochenkov mentioned this issue Jul 1, 2020
Merged
uqs pushed a commit to freebsd/freebsd-ports that referenced this issue Apr 1, 2021
@jbeich
MFH: r486650
9937282 
textproc/ripgrep: unbreak AVX=on on i386 after r454995

error[E0432]: unresolved import `simd::x86::avx`
  --> cargo-crates/bytecount-0.3.2/src/lib.rs:49:16
   |
49 | use simd::x86::avx::{LowHigh128, u8x32};
   |                ^^^ could not find `avx` in `x86`

rust-lang/rust#56527

Approved by:	ports-secteam blanket
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cmdline: Make target features individually overridable petrochenkov/rust
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@cuviper @jonas-schievink @petrochenkov @jbeich