Sync from rust 2023 06 11 #282
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Now that we require at least LLVM 13, that codegen backend is always using its intrinsic `fptosi.sat` and `fptoui.sat` conversions, so it doesn't need the manual implementation. However, the GCC backend still needs it, so we can move all of that code down there.
Because `PassMode::Cast` is by far the largest variant, but is relatively rare. This requires making `PassMode` not impl `Copy`, and `Clone` is no longer necessary. This causes lots of sigil adjusting, but nothing very notable.
Currently they try to be very precise. But they are wrong, i.e. they don't match what's happening in the loop below. This code isn't hot enough for it to matter that much.
Because it's only ever set to `None` or `Some(Reg::i32())`.
Because it's only needed for that variant. This shrinks the types and clarifies the logic.
Shrink `FnAbi` Because they can take up a lot of memory in debug and release builds. r? `@bjorn3`
Add pointer masking convenience functions
This PR adds the following public API:
```rust
impl<T: ?Sized> *const T {
fn mask(self, mask: usize) -> *const T;
}
impl<T: ?Sized> *mut T {
fn mask(self, mask: usize) -> *const T;
}
// mod intrinsics
fn mask<T>(ptr: *const T, mask: usize) -> *const T
```
This is equivalent to `ptr.map_addr(|a| a & mask)` but also uses a cool llvm intrinsic.
Proposed in rust-lang/rust#95643 (comment)
cc `@Gankra` `@scottmcm` `@RalfJung`
r? rust-lang/libs-api
interpret: make read-pointer-as-bytes a CTFE-only error with extra information Next step in the reaction to rust-lang/rust#99923. Also teaches Miri to implicitly strip provenance in more situations when transmuting pointers to integers, which fixes rust-lang/miri#2456. Pointer-to-int transmutation during CTFE now produces a message like this: ``` = help: this code performed an operation that depends on the underlying bytes representing a pointer = help: the absolute address of a pointer is not known at compile-time, so such operations are not supported ``` r? ``@oli-obk``
Move the cast_float_to_int fallback code to GCC Now that we require at least LLVM 13, that codegen backend is always using its intrinsic `fptosi.sat` and `fptoui.sat` conversions, so it doesn't need the manual implementation. However, the GCC backend still needs it, so we can move all of that code down there.
Optimize scalar and scalar pair representations loaded from ByRef in llvm in rust-lang/rust#105653 I noticed that we were generating suboptimal LLVM IR if we had a `ConstValue::ByRef` that could be represented by a `ScalarPair`. Before rust-lang/rust#105653 this is probably rare, but after it, every slice will go down this suboptimal code path that requires LLVM to untangle a bunch of indirections and translate static allocations that are only used once to read a scalar pair from.
These tend to have special handling in a bunch of places anyway, so the variant helps remember that. And I think it's easier to grok than non-Scalar Aggregates sometimes being `Immediates` (like I got wrong and caused 109992). As a minor bonus, it means we don't need to generate poison LLVM values for them to pass around in `OperandValue::Immediate`s.
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