db188b33b3
This commit adds the OS-independent extension implication logic for RISC-V.
It implements:
1. Regular implication (A → B)
a. "the extension A implies the extension B"
b. "the extension A requires the extension B"
c. "the extension A depends on the extension B"
2. Extension group or shorthand (A == B1 & B2...)
a. "the extension A is shorthand for other extensions: B1, B2..."
b. "the extension A comprises instructions provided by B1, B2..."
This is implemented as (A → B1 & B2... + B1 & B2... → A)
where the former is a regular implication as required by specifications
and the latter is a "reverse" implication to improve usability.
and prepares for:
3. Implication with multiple requirements (A1 & A2... → B)
a. "A1 + A2 implies B"
b. (implicitly used to implement reverse implication of case 2)
Although it uses macros and iterators, good optimizers turn the series of
implications into fast bit-manipulation operations.
In the case 2 (extension group or shorthand; where a superset extension
is just a collection of other subextensions and provides no features by
a superset itself), specifications do specify that an extension group
implies its members but not vice versa. However, implying an extension
group from its members would improve usability on the feature detection
(especially when the feature provider does not provide existence of such
extension group but provides existence of its members).
Similar "reverse implication" on RISC-V is implemented on LLVM.
Case 3 is implicitly used to implement reverse implication of case 2 but
there's another use case: implication with multiple requirements like
"Zcf" and "Zcd" extensions (not yet implemented in this crate for now).
To handle extension groups perfectly, we need to loop implication several
times (until they converge; normally 2 times and up to 4 times when we add
most of `riscv_hwprobe`-based features).
To make implementation of that loop possible, `cache::Initializer` is
modified to implement `PartialEq` and `Eq`.
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| .github/workflows | ||
| ci | ||
| crates | ||
| examples | ||
| intrinsics_data | ||
| .cirrus.yml | ||
| .git-blame-ignore-revs | ||
| .gitignore | ||
| .gitmodules | ||
| Cargo.toml | ||
| CONTRIBUTING.md | ||
| LICENSE-APACHE | ||
| LICENSE-MIT | ||
| README.md | ||
| rustfmt.toml | ||
| triagebot.toml | ||
| vendor.yml | ||
stdarch - Rust's standard library SIMD components
Crates
This repository contains two main crates:
-
core_archimplementscore::arch- Rust's core library architecture-specific intrinsics, and -
std_detectimplementsstd::detect- Rust's standard library run-time CPU feature detection.
The std::simd component now lives in the
packed_simd_2 crate.