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Rollup merge of #100371 - xfix:inline-from-bytes-with-nul-unchecked-rt-impl, r=scottmcm

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Inline CStr::from_bytes_with_nul_unchecked::rt_impl

Currently `CStr::from_bytes_with_nul_unchecked::rt_impl` is not being inlined. The following function:

```rust
pub unsafe fn from_bytes_with_nul_unchecked(bytes: &[u8]) {
    CStr::from_bytes_with_nul_unchecked(bytes);
}
```

Outputs the following assembly on current nightly

```asm
example::from_bytes_with_nul_unchecked:
        jmp     qword ptr [rip + _ZN4core3ffi5c_str4CStr29from_bytes_with_nul_unchecked7rt_impl17h026f29f3d6a41333E@GOTPCREL]
```

Meanwhile on beta this provides the following assembly:

```asm
example::from_bytes_with_nul_unchecked:
        ret
```

This pull request adds `#[inline]` annotation to`rt_impl` to fix a code generation regression for `CStr::from_bytes_with_nul_unchecked`.
This commit is contained in:
Michael Goulet 2022-08-10 09:28:25 -07:00 committed by GitHub
commit eff71b9927
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library/core/src/ffi/c_str.rs
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@ -387,6 +387,7 @@ impl CStr {
#[rustc_const_stable(feature = "const_cstr_unchecked", since = "1.59.0")] #[rustc_const_stable(feature = "const_cstr_unchecked", since = "1.59.0")]
#[rustc_allow_const_fn_unstable(const_eval_select)] #[rustc_allow_const_fn_unstable(const_eval_select)]
pub const unsafe fn from_bytes_with_nul_unchecked(bytes: &[u8]) -> &CStr { pub const unsafe fn from_bytes_with_nul_unchecked(bytes: &[u8]) -> &CStr {
#[inline]
fn rt_impl(bytes: &[u8]) -> &CStr { fn rt_impl(bytes: &[u8]) -> &CStr {
// Chance at catching some UB at runtime with debug builds. // Chance at catching some UB at runtime with debug builds.
debug_assert!(!bytes.is_empty() && bytes[bytes.len() - 1] == 0); debug_assert!(!bytes.is_empty() && bytes[bytes.len() - 1] == 0);