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Refactoring after the PlaceValue addition
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I added `PlaceValue` in 123775, but kept that one line-by-line simple because it touched so many places.

This goes through to add more helpers & docs, and change some `PlaceRef` to `PlaceValue` where the type didn't need to be included.

No behaviour changes.
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@scottmcm
scottmcm committed Apr 19, 2024
1 parent fa0068b commit 7445e66
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Showing 7 changed files with 138 additions and 115 deletions.
2 changes: 1 addition & 1 deletion compiler/rustc_codegen_ssa/src/base.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -282,7 +282,7 @@ pub fn coerce_unsized_into<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
}

if src_f.layout.ty == dst_f.layout.ty {
bx.typed_place_copy(dst_f, src_f);
bx.typed_place_copy(dst_f.val, src_f.val, src_f.layout);
} else {
coerce_unsized_into(bx, src_f, dst_f);
}
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5 changes: 2 additions & 3 deletions compiler/rustc_codegen_ssa/src/mir/block.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1472,8 +1472,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
// alignment requirements may be higher than the type's alignment, so copy
// to a higher-aligned alloca.
let scratch = PlaceRef::alloca_aligned(bx, arg.layout, required_align);
let op_place = PlaceRef { val: op_place_val, layout: op.layout };
bx.typed_place_copy(scratch, op_place);
bx.typed_place_copy(scratch.val, op_place_val, op.layout);
(scratch.val.llval, scratch.val.align, true)
} else {
(op_place_val.llval, op_place_val.align, true)
Expand Down Expand Up @@ -1563,7 +1562,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
if place_val.llextra.is_some() {
bug!("closure arguments must be sized");
}
let tuple_ptr = PlaceRef { val: place_val, layout: tuple.layout };
let tuple_ptr = place_val.with_type(tuple.layout);
for i in 0..tuple.layout.fields.count() {
let field_ptr = tuple_ptr.project_field(bx, i);
let field = bx.load_operand(field_ptr);
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15 changes: 7 additions & 8 deletions compiler/rustc_codegen_ssa/src/mir/intrinsic.rs
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Original file line number Diff line number Diff line change
@@ -1,4 +1,4 @@
use super::operand::{OperandRef, OperandValue};
use super::operand::OperandRef;
use super::place::PlaceRef;
use super::FunctionCx;
use crate::errors;
Expand Down Expand Up @@ -92,9 +92,10 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
// into the (unoptimized) direct swapping implementation, so we disable it.
|| bx.sess().target.arch == "spirv"
{
let x_place = PlaceRef::new_sized(args[0].immediate(), pointee_layout);
let y_place = PlaceRef::new_sized(args[1].immediate(), pointee_layout);
bx.typed_place_swap(x_place, y_place);
let align = pointee_layout.align.abi;
let x_place = args[0].val.deref(align);
let y_place = args[1].val.deref(align);
bx.typed_place_swap(x_place, y_place, pointee_layout);
return Ok(());
}
}
Expand All @@ -112,15 +113,13 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
sym::va_end => bx.va_end(args[0].immediate()),
sym::size_of_val => {
let tp_ty = fn_args.type_at(0);
let meta =
if let OperandValue::Pair(_, meta) = args[0].val { Some(meta) } else { None };
let (_, meta) = args[0].val.pointer_parts();
let (llsize, _) = size_of_val::size_and_align_of_dst(bx, tp_ty, meta);
llsize
}
sym::min_align_of_val => {
let tp_ty = fn_args.type_at(0);
let meta =
if let OperandValue::Pair(_, meta) = args[0].val { Some(meta) } else { None };
let (_, meta) = args[0].val.pointer_parts();
let (_, llalign) = size_of_val::size_and_align_of_dst(bx, tp_ty, meta);
llalign
}
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47 changes: 37 additions & 10 deletions compiler/rustc_codegen_ssa/src/mir/operand.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -57,6 +57,32 @@ pub enum OperandValue<V> {
ZeroSized,
}

impl<V: CodegenObject> OperandValue<V> {
/// Treat this value as a pointer and return the data pointer and
/// optional metadata as backend values.
///
/// If you're making a place, use [`Self::deref`] instead.
pub fn pointer_parts(self) -> (V, Option<V>) {
match self {
OperandValue::Immediate(llptr) => (llptr, None),
OperandValue::Pair(llptr, llextra) => (llptr, Some(llextra)),
_ => bug!("OperandValue cannot be a pointer: {self:?}"),
}
}

/// Treat this value as a pointer and return the place to which it points.
///
/// The pointer immediate doesn't inherently know its alignment,
/// so you need to pass it in. If you want to get it from a type's ABI
/// alignment, then maybe you want [`OperandRef::deref`] instead.
///
/// This is the inverse of [`PlaceValue::address`].
pub fn deref(self, align: Align) -> PlaceValue<V> {
let (llval, llextra) = self.pointer_parts();
PlaceValue { llval, llextra, align }
}
}

/// An `OperandRef` is an "SSA" reference to a Rust value, along with
/// its type.
///
Expand Down Expand Up @@ -204,6 +230,15 @@ impl<'a, 'tcx, V: CodegenObject> OperandRef<'tcx, V> {
}
}

/// Asserts that this operand is a pointer (or reference) and returns
/// the place to which it points. (This requires no code to be emitted
/// as we represent places using the pointer to the place.)
///
/// This uses [`Ty::builtin_deref`] to include the type of the place and
/// assumes the place is aligned to the pointee's usual ABI alignment.
///
/// If you don't need the type, see [`OperandValue::pointer_parts`]
/// or [`OperandValue::deref`].
pub fn deref<Cx: LayoutTypeMethods<'tcx>>(self, cx: &Cx) -> PlaceRef<'tcx, V> {
if self.layout.ty.is_box() {
// Derefer should have removed all Box derefs
Expand All @@ -217,15 +252,8 @@ impl<'a, 'tcx, V: CodegenObject> OperandRef<'tcx, V> {
.unwrap_or_else(|| bug!("deref of non-pointer {:?}", self))
.ty;

let (llptr, llextra) = match self.val {
OperandValue::Immediate(llptr) => (llptr, None),
OperandValue::Pair(llptr, llextra) => (llptr, Some(llextra)),
OperandValue::Ref(..) => bug!("Deref of by-Ref operand {:?}", self),
OperandValue::ZeroSized => bug!("Deref of ZST operand {:?}", self),
};
let layout = cx.layout_of(projected_ty);
let val = PlaceValue { llval: llptr, llextra, align: layout.align.abi };
PlaceRef { val, layout }
self.val.deref(layout.align.abi).with_type(layout)
}

/// If this operand is a `Pair`, we return an aggregate with the two values.
Expand Down Expand Up @@ -418,8 +446,7 @@ impl<'a, 'tcx, V: CodegenObject> OperandValue<V> {
if val.llextra.is_some() {
bug!("cannot directly store unsized values");
}
let source_place = PlaceRef { val, layout: dest.layout };
bx.typed_place_copy_with_flags(dest, source_place, flags);
bx.typed_place_copy_with_flags(dest.val, val, dest.layout, flags);
}
OperandValue::Immediate(s) => {
let val = bx.from_immediate(s);
Expand Down
71 changes: 41 additions & 30 deletions compiler/rustc_codegen_ssa/src/mir/place.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -15,6 +15,9 @@ use rustc_target::abi::{VariantIdx, Variants};
/// The location and extra runtime properties of the place.
///
/// Typically found in a [`PlaceRef`] or an [`OperandValue::Ref`].
///
/// As a location in memory, this has no specific type. If you want to
/// load or store it using a typed operation, use [`Self::with_type`].
#[derive(Copy, Clone, Debug)]
pub struct PlaceValue<V> {
/// A pointer to the contents of the place.
Expand All @@ -34,6 +37,28 @@ impl<V: CodegenObject> PlaceValue<V> {
pub fn new_sized(llval: V, align: Align) -> PlaceValue<V> {
PlaceValue { llval, llextra: None, align }
}

/// Creates a `PlaceRef` to this location with the given type.
pub fn with_type<'tcx>(self, layout: TyAndLayout<'tcx>) -> PlaceRef<'tcx, V> {
debug_assert!(
layout.is_unsized() || layout.abi.is_uninhabited() || self.llextra.is_none(),
"Had pointer metadata {:?} for sized type {layout:?}",
self.llextra,
);
PlaceRef { val: self, layout }
}

/// Gets the pointer to this place as an [`OperandValue::Immediate`]
/// or, for those needing metadata, an [`OperandValue::Pair`].
///
/// This is the inverse of [`OperandValue::deref`].
pub fn address(self) -> OperandValue<V> {
if let Some(llextra) = self.llextra {
OperandValue::Pair(self.llval, llextra)
} else {
OperandValue::Immediate(self.llval)
}
}
}

#[derive(Copy, Clone, Debug)]
Expand All @@ -51,9 +76,7 @@ pub struct PlaceRef<'tcx, V> {

impl<'a, 'tcx, V: CodegenObject> PlaceRef<'tcx, V> {
pub fn new_sized(llval: V, layout: TyAndLayout<'tcx>) -> PlaceRef<'tcx, V> {
assert!(layout.is_sized());
let val = PlaceValue::new_sized(llval, layout.align.abi);
PlaceRef { val, layout }
PlaceRef::new_sized_aligned(llval, layout, layout.align.abi)
}

pub fn new_sized_aligned(
Expand All @@ -62,8 +85,7 @@ impl<'a, 'tcx, V: CodegenObject> PlaceRef<'tcx, V> {
align: Align,
) -> PlaceRef<'tcx, V> {
assert!(layout.is_sized());
let val = PlaceValue::new_sized(llval, align);
PlaceRef { val, layout }
PlaceValue::new_sized(llval, align).with_type(layout)
}

// FIXME(eddyb) pass something else for the name so no work is done
Expand Down Expand Up @@ -131,18 +153,12 @@ impl<'a, 'tcx, V: CodegenObject> PlaceRef<'tcx, V> {
} else {
bx.inbounds_ptradd(self.val.llval, bx.const_usize(offset.bytes()))
};
PlaceRef {
val: PlaceValue {
llval,
llextra: if bx.cx().type_has_metadata(field.ty) {
self.val.llextra
} else {
None
},
align: effective_field_align,
},
layout: field,
}
let val = PlaceValue {
llval,
llextra: if bx.cx().type_has_metadata(field.ty) { self.val.llextra } else { None },
align: effective_field_align,
};
val.with_type(field)
};

// Simple cases, which don't need DST adjustment:
Expand Down Expand Up @@ -197,7 +213,7 @@ impl<'a, 'tcx, V: CodegenObject> PlaceRef<'tcx, V> {
let ptr = bx.inbounds_ptradd(self.val.llval, offset);
let val =
PlaceValue { llval: ptr, llextra: self.val.llextra, align: effective_field_align };
PlaceRef { val, layout: field }
val.with_type(field)
}

/// Obtain the actual discriminant of a value.
Expand Down Expand Up @@ -386,18 +402,13 @@ impl<'a, 'tcx, V: CodegenObject> PlaceRef<'tcx, V> {
layout.size
};

PlaceRef {
val: PlaceValue {
llval: bx.inbounds_gep(
bx.cx().backend_type(self.layout),
self.val.llval,
&[bx.cx().const_usize(0), llindex],
),
llextra: None,
align: self.val.align.restrict_for_offset(offset),
},
layout,
}
let llval = bx.inbounds_gep(
bx.cx().backend_type(self.layout),
self.val.llval,
&[bx.cx().const_usize(0), llindex],
);
let align = self.val.align.restrict_for_offset(offset);
PlaceValue::new_sized(llval, align).with_type(layout)
}

pub fn project_downcast<Bx: BuilderMethods<'a, 'tcx, Value = V>>(
Expand Down
52 changes: 14 additions & 38 deletions compiler/rustc_codegen_ssa/src/mir/rvalue.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -72,8 +72,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
if val.llextra.is_some() {
bug!("unsized coercion on an unsized rvalue");
}
let source = PlaceRef { val, layout: operand.layout };
base::coerce_unsized_into(bx, source, dest);
base::coerce_unsized_into(bx, val.with_type(operand.layout), dest);
}
OperandValue::ZeroSized => {
bug!("unsized coercion on a ZST rvalue");
Expand Down Expand Up @@ -182,10 +181,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
OperandValue::Immediate(..) | OperandValue::Pair(..) => {
// When we have immediate(s), the alignment of the source is irrelevant,
// so we can store them using the destination's alignment.
src.val.store(
bx,
PlaceRef::new_sized_aligned(dst.val.llval, src.layout, dst.val.align),
);
src.val.store(bx, dst.val.with_type(src.layout));
}
}
}
Expand Down Expand Up @@ -223,8 +219,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
OperandValue::Ref(source_place_val) => {
debug_assert_eq!(source_place_val.llextra, None);
debug_assert!(matches!(operand_kind, OperandValueKind::Ref));
let fake_place = PlaceRef { val: source_place_val, layout: cast };
Some(bx.load_operand(fake_place).val)
Some(bx.load_operand(source_place_val.with_type(cast)).val)
}
OperandValue::ZeroSized => {
let OperandValueKind::ZeroSized = operand_kind else {
Expand Down Expand Up @@ -452,23 +447,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
}
mir::CastKind::PointerCoercion(PointerCoercion::Unsize) => {
assert!(bx.cx().is_backend_scalar_pair(cast));
let (lldata, llextra) = match operand.val {
OperandValue::Pair(lldata, llextra) => {
// unsize from a fat pointer -- this is a
// "trait-object-to-supertrait" coercion.
(lldata, Some(llextra))
}
OperandValue::Immediate(lldata) => {
// "standard" unsize
(lldata, None)
}
OperandValue::Ref(..) => {
bug!("by-ref operand {:?} in `codegen_rvalue_operand`", operand);
}
OperandValue::ZeroSized => {
bug!("zero-sized operand {:?} in `codegen_rvalue_operand`", operand);
}
};
let (lldata, llextra) = operand.val.pointer_parts();
let (lldata, llextra) =
base::unsize_ptr(bx, lldata, operand.layout.ty, cast.ty, llextra);
OperandValue::Pair(lldata, llextra)
Expand All @@ -489,12 +468,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
}
}
mir::CastKind::DynStar => {
let (lldata, llextra) = match operand.val {
OperandValue::Ref(..) => todo!(),
OperandValue::Immediate(v) => (v, None),
OperandValue::Pair(v, l) => (v, Some(l)),
OperandValue::ZeroSized => bug!("ZST -- which is not PointerLike -- in DynStar"),
};
let (lldata, llextra) = operand.val.pointer_parts();
let (lldata, llextra) =
base::cast_to_dyn_star(bx, lldata, operand.layout, cast.ty, llextra);
OperandValue::Pair(lldata, llextra)
Expand Down Expand Up @@ -762,16 +736,18 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
mk_ptr_ty: impl FnOnce(TyCtxt<'tcx>, Ty<'tcx>) -> Ty<'tcx>,
) -> OperandRef<'tcx, Bx::Value> {
let cg_place = self.codegen_place(bx, place.as_ref());
let val = cg_place.val.address();

let ty = cg_place.layout.ty;
debug_assert!(
if bx.cx().type_has_metadata(ty) {
matches!(val, OperandValue::Pair(..))
} else {
matches!(val, OperandValue::Immediate(..))
},
"Address of place was unexpectedly {val:?} for pointee type {ty:?}",
);

// Note: places are indirect, so storing the `llval` into the
// destination effectively creates a reference.
let val = if !bx.cx().type_has_metadata(ty) {
OperandValue::Immediate(cg_place.val.llval)
} else {
OperandValue::Pair(cg_place.val.llval, cg_place.val.llextra.unwrap())
};
OperandRef { val, layout: self.cx.layout_of(mk_ptr_ty(self.cx.tcx(), ty)) }
}

Expand Down
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