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More GVN for PtrMetadata

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`PtrMetadata` doesn't care about `*const`/`*mut`/`&`/`&mut`, so GVN away those casts in its argument.

This includes updating MIR to allow calling PtrMetadata on references too, not just raw pointers.  That means that `[T]::len` can be just `_0 = PtrMetadata(_1)`, for example.

# Conflicts:
#	tests/mir-opt/pre-codegen/slice_index.slice_get_unchecked_mut_range.PreCodegen.after.panic-abort.mir
#	tests/mir-opt/pre-codegen/slice_index.slice_get_unchecked_mut_range.PreCodegen.after.panic-unwind.mir
This commit is contained in:
Scott McMurray 2024-06-19 22:14:31 -07:00
parent 31d8696ac9
commit 4a7b6c0e6c
14 changed files with 319 additions and 78 deletions
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6
compiler/rustc_middle/src/mir/syntax.rs
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@ -1446,10 +1446,12 @@ pub enum UnOp {
Not,
/// The `-` operator for negation
Neg,
/// Get the metadata `M` from a `*const/mut impl Pointee<Metadata = M>`.
/// Gets the metadata `M` from a `*const`/`*mut`/`&`/`&mut` to
/// `impl Pointee<Metadata = M>`.
///
/// For example, this will give a `()` from `*const i32`, a `usize` from
/// `*mut [u8]`, or a pointer to a vtable from a `*const dyn Foo`.
/// `&mut [u8]`, or a `ptr::DynMetadata<dyn Foo>` (internally a pointer)
/// from a `*mut dyn Foo`.
///
/// Allowed only in [`MirPhase::Runtime`]; earlier it's an intrinsic.
PtrMetadata,