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Rollup merge of #115654 - RalfJung:pass-mode-cast, r=compiler-errors

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improve PassMode docs
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Dylan DPC 2023-09-17 11:23:25 +00:00 • committed by GitHub
commit 0c5f5b6db7
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12 changed files with 118 additions and 96 deletions
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58
compiler/rustc_target/src/abi/call/mod.rs
View file

@ -46,17 +46,17 @@ pub enum PassMode {
///
/// The argument has a layout abi of `ScalarPair`.
Pair(ArgAttributes, ArgAttributes),
/// Pass the argument after casting it, to either a single uniform or a
/// pair of registers. The bool indicates if a `Reg::i32()` dummy argument
/// is emitted before the real argument.
Cast(Box<CastTarget>, bool),
/// Pass the argument after casting it. See the `CastTarget` docs for details. The bool
/// indicates if a `Reg::i32()` dummy argument is emitted before the real argument.
Cast { pad_i32: bool, cast: Box<CastTarget> },
/// Pass the argument indirectly via a hidden pointer.
/// The `extra_attrs` value, if any, is for the extra data (vtable or length)
/// which indicates that it refers to an unsized rvalue.
/// `on_stack` defines that the value should be passed at a fixed
/// stack offset in accordance to the ABI rather than passed using a
/// pointer. This corresponds to the `byval` LLVM argument attribute.
Indirect { attrs: ArgAttributes, extra_attrs: Option<ArgAttributes>, on_stack: bool },
/// The `meta_attrs` value, if any, is for the metadata (vtable or length) of an unsized
/// argument. (This is the only mode that supports unsized arguments.)
/// `on_stack` defines that the value should be passed at a fixed stack offset in accordance to
/// the ABI rather than passed using a pointer. This corresponds to the `byval` LLVM argument
/// attribute (using the Rust type of this argument). `on_stack` cannot be true for unsized
/// arguments, i.e., when `meta_attrs` is `Some`.
Indirect { attrs: ArgAttributes, meta_attrs: Option<ArgAttributes>, on_stack: bool },
}
impl PassMode {
@ -65,17 +65,20 @@ impl PassMode {
/// so that needs to be compared as well!
pub fn eq_abi(&self, other: &Self) -> bool {
match (self, other) {
(PassMode::Ignore, PassMode::Ignore) => true, // can still be reached for the return type
(PassMode::Ignore, PassMode::Ignore) => true,
(PassMode::Direct(a1), PassMode::Direct(a2)) => a1.eq_abi(a2),
(PassMode::Pair(a1, b1), PassMode::Pair(a2, b2)) => a1.eq_abi(a2) && b1.eq_abi(b2),
(PassMode::Cast(c1, pad1), PassMode::Cast(c2, pad2)) => c1.eq_abi(c2) && pad1 == pad2,
(
PassMode::Indirect { attrs: a1, extra_attrs: None, on_stack: s1 },
PassMode::Indirect { attrs: a2, extra_attrs: None, on_stack: s2 },
PassMode::Cast { cast: c1, pad_i32: pad1 },
PassMode::Cast { cast: c2, pad_i32: pad2 },
) => c1.eq_abi(c2) && pad1 == pad2,
(
PassMode::Indirect { attrs: a1, meta_attrs: None, on_stack: s1 },
PassMode::Indirect { attrs: a2, meta_attrs: None, on_stack: s2 },
) => a1.eq_abi(a2) && s1 == s2,
(
PassMode::Indirect { attrs: a1, extra_attrs: Some(e1), on_stack: s1 },
PassMode::Indirect { attrs: a2, extra_attrs: Some(e2), on_stack: s2 },
PassMode::Indirect { attrs: a1, meta_attrs: Some(e1), on_stack: s1 },
PassMode::Indirect { attrs: a2, meta_attrs: Some(e2), on_stack: s2 },
) => a1.eq_abi(a2) && e1.eq_abi(e2) && s1 == s2,
_ => false,
}
@ -256,6 +259,13 @@ impl Uniform {
}
}
/// Describes the type used for `PassMode::Cast`.
///
/// Passing arguments in this mode works as follows: the registers in the `prefix` (the ones that
/// are `Some`) get laid out one after the other (using `repr(C)` layout rules). Then the
/// `rest.unit` register type gets repeated often enough to cover `rest.size`. This describes the
/// actual type used for the call; the Rust type of the argument is then transmuted to this ABI type
/// (and all data in the padding between the registers is dropped).
#[derive(Clone, PartialEq, Eq, Hash, Debug, HashStable_Generic)]
pub struct CastTarget {
pub prefix: [Option<Reg>; 8],
@ -565,15 +575,15 @@ impl<'a, Ty> ArgAbi<'a, Ty> {
attrs.pointee_size = layout.size;
attrs.pointee_align = Some(layout.align.abi);
let extra_attrs = layout.is_unsized().then_some(ArgAttributes::new());
let meta_attrs = layout.is_unsized().then_some(ArgAttributes::new());
PassMode::Indirect { attrs, extra_attrs, on_stack: false }
PassMode::Indirect { attrs, meta_attrs, on_stack: false }
}
pub fn make_indirect(&mut self) {
match self.mode {
PassMode::Direct(_) | PassMode::Pair(_, _) => {}
PassMode::Indirect { attrs: _, extra_attrs: None, on_stack: false } => return,
PassMode::Indirect { attrs: _, meta_attrs: None, on_stack: false } => return,
_ => panic!("Tried to make {:?} indirect", self.mode),
}
@ -583,7 +593,7 @@ impl<'a, Ty> ArgAbi<'a, Ty> {
pub fn make_indirect_byval(&mut self, byval_align: Option<Align>) {
self.make_indirect();
match self.mode {
PassMode::Indirect { ref mut attrs, extra_attrs: _, ref mut on_stack } => {
PassMode::Indirect { ref mut attrs, meta_attrs: _, ref mut on_stack } => {
*on_stack = true;
// Some platforms, like 32-bit x86, change the alignment of the type when passing
@ -616,11 +626,11 @@ impl<'a, Ty> ArgAbi<'a, Ty> {
}
pub fn cast_to<T: Into<CastTarget>>(&mut self, target: T) {
self.mode = PassMode::Cast(Box::new(target.into()), false);
self.mode = PassMode::Cast { cast: Box::new(target.into()), pad_i32: false };
}
pub fn cast_to_and_pad_i32<T: Into<CastTarget>>(&mut self, target: T, pad_i32: bool) {
self.mode = PassMode::Cast(Box::new(target.into()), pad_i32);
self.mode = PassMode::Cast { cast: Box::new(target.into()), pad_i32 };
}
pub fn is_indirect(&self) -> bool {
@ -628,11 +638,11 @@ impl<'a, Ty> ArgAbi<'a, Ty> {
}
pub fn is_sized_indirect(&self) -> bool {
matches!(self.mode, PassMode::Indirect { attrs: _, extra_attrs: None, on_stack: _ })
matches!(self.mode, PassMode::Indirect { attrs: _, meta_attrs: None, on_stack: _ })
}
pub fn is_unsized_indirect(&self) -> bool {
matches!(self.mode, PassMode::Indirect { attrs: _, extra_attrs: Some(_), on_stack: _ })
matches!(self.mode, PassMode::Indirect { attrs: _, meta_attrs: Some(_), on_stack: _ })
}
pub fn is_ignore(&self) -> bool {

6
compiler/rustc_target/src/abi/call/x86.rs
View file

@ -142,13 +142,13 @@ where
for arg in fn_abi.args.iter_mut() {
let attrs = match arg.mode {
PassMode::Ignore
| PassMode::Indirect { attrs: _, extra_attrs: None, on_stack: _ } => {
| PassMode::Indirect { attrs: _, meta_attrs: None, on_stack: _ } => {
continue;
}
PassMode::Direct(ref mut attrs) => attrs,
PassMode::Pair(..)
| PassMode::Indirect { attrs: _, extra_attrs: Some(_), on_stack: _ }
| PassMode::Cast(..) => {
| PassMode::Indirect { attrs: _, meta_attrs: Some(_), on_stack: _ }
| PassMode::Cast { .. } => {
unreachable!("x86 shouldn't be passing arguments by {:?}", arg.mode)
}
};