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Auto merge of rust-lang#124999 - scottmcm:unify-aggregate, r=nnethercote
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Unify `Rvalue::Aggregate` paths in cg_ssa

In rust-lang#123840 and rust-lang#123886 I added two different codepaths for `Rvalue::Aggregate` in `cg_ssa`.

This merges them into one, since raw pointers are also immediates that can be built from the immediates of their "fields".
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bors committed May 13, 2024
2 parents 982c9c1 + 99213ae commit 6be7b0c
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Showing 4 changed files with 26 additions and 22 deletions.
9 changes: 7 additions & 2 deletions compiler/rustc_abi/src/lib.rs
Original file line number Diff line number Diff line change
Expand Up @@ -1255,7 +1255,7 @@ impl<FieldIdx: Idx> FieldsShape<FieldIdx> {

/// Gets source indices of the fields by increasing offsets.
#[inline]
pub fn index_by_increasing_offset(&self) -> impl Iterator<Item = usize> + '_ {
pub fn index_by_increasing_offset(&self) -> impl ExactSizeIterator<Item = usize> + '_ {
let mut inverse_small = [0u8; 64];
let mut inverse_big = IndexVec::new();
let use_small = self.count() <= inverse_small.len();
Expand All @@ -1271,7 +1271,12 @@ impl<FieldIdx: Idx> FieldsShape<FieldIdx> {
}
}

(0..self.count()).map(move |i| match *self {
// Primitives don't really have fields in the way that structs do,
// but having this return an empty iterator for them is unhelpful
// since that makes them look kinda like ZSTs, which they're not.
let pseudofield_count = if let FieldsShape::Primitive = self { 1 } else { self.count() };

(0..pseudofield_count).map(move |i| match *self {
FieldsShape::Primitive | FieldsShape::Union(_) | FieldsShape::Array { .. } => i,
FieldsShape::Arbitrary { .. } => {
if use_small {
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13 changes: 13 additions & 0 deletions compiler/rustc_codegen_ssa/src/mir/operand.rs
Original file line number Diff line number Diff line change
Expand Up @@ -110,6 +110,19 @@ impl<V: CodegenObject> OperandValue<V> {
let (llval, llextra) = self.pointer_parts();
PlaceValue { llval, llextra, align }
}

pub(crate) fn is_expected_variant_for_type<'tcx, Cx: LayoutTypeMethods<'tcx>>(
&self,
cx: &Cx,
ty: TyAndLayout<'tcx>,
) -> bool {
match self {
OperandValue::ZeroSized => ty.is_zst(),
OperandValue::Immediate(_) => cx.is_backend_immediate(ty),
OperandValue::Pair(_, _) => cx.is_backend_scalar_pair(ty),
OperandValue::Ref(_) => cx.is_backend_ref(ty),
}
}
}

/// An `OperandRef` is an "SSA" reference to a Rust value, along with
Expand Down
24 changes: 5 additions & 19 deletions compiler/rustc_codegen_ssa/src/mir/rvalue.rs
Original file line number Diff line number Diff line change
Expand Up @@ -696,24 +696,6 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
OperandRef { val: OperandValue::Immediate(static_), layout }
}
mir::Rvalue::Use(ref operand) => self.codegen_operand(bx, operand),
mir::Rvalue::Aggregate(box mir::AggregateKind::RawPtr(..), ref fields) => {
let ty = rvalue.ty(self.mir, self.cx.tcx());
let layout = self.cx.layout_of(self.monomorphize(ty));
let [data, meta] = &*fields.raw else {
bug!("RawPtr fields: {fields:?}");
};
let data = self.codegen_operand(bx, data);
let meta = self.codegen_operand(bx, meta);
match (data.val, meta.val) {
(p @ OperandValue::Immediate(_), OperandValue::ZeroSized) => {
OperandRef { val: p, layout }
}
(OperandValue::Immediate(p), OperandValue::Immediate(m)) => {
OperandRef { val: OperandValue::Pair(p, m), layout }
}
_ => bug!("RawPtr operands {data:?} {meta:?}"),
}
}
mir::Rvalue::Repeat(..) => bug!("{rvalue:?} in codegen_rvalue_operand"),
mir::Rvalue::Aggregate(_, ref fields) => {
let ty = rvalue.ty(self.mir, self.cx.tcx());
Expand Down Expand Up @@ -748,6 +730,10 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
);

let val = OperandValue::from_immediates(inputs);
debug_assert!(
val.is_expected_variant_for_type(self.cx, layout),
"Made wrong variant {val:?} for type {layout:?}",
);
OperandRef { val, layout }
}
mir::Rvalue::ShallowInitBox(ref operand, content_ty) => {
Expand Down Expand Up @@ -792,7 +778,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
debug_assert!(
if bx.cx().type_has_metadata(ty) {
matches!(val, OperandValue::Pair(..))
} else {
} else {
matches!(val, OperandValue::Immediate(..))
},
"Address of place was unexpectedly {val:?} for pointee type {ty:?}",
Expand Down
2 changes: 1 addition & 1 deletion tests/codegen/mir-aggregate-no-alloca.rs
Original file line number Diff line number Diff line change
Expand Up @@ -55,7 +55,7 @@ pub fn make_cell_of_bool(b: bool) -> std::cell::Cell<bool> {
std::cell::Cell::new(b)
}

// CHECK-LABLE: { i8, i16 } @make_cell_of_bool_and_short(i1 noundef zeroext %b, i16 noundef %s)
// CHECK-LABEL: { i8, i16 } @make_cell_of_bool_and_short(i1 noundef zeroext %b, i16 noundef %s)
#[no_mangle]
pub fn make_cell_of_bool_and_short(b: bool, s: u16) -> std::cell::Cell<(bool, u16)> {
// CHECK-NOT: alloca
Expand Down

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