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Rework OperandRef::extract_field to stop calling to_immediate_scalar on things which are already immediates

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That means it stops trying to truncate things that are already `i1`s.
This commit is contained in:
Scott McMurray
2025-02-15 16:07:18 -08:00
parent 642a705f71
commit 6f9cfd694d
9 changed files with 164 additions and 87 deletions
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131
compiler/rustc_codegen_ssa/src/mir/operand.rs
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@@ -1,15 +1,14 @@
use std::assert_matches::assert_matches;
use std::fmt;
use arrayvec::ArrayVec;
use either::Either;
use rustc_abi as abi;
use rustc_abi::{Align, BackendRepr, Size};
use rustc_middle::bug;
use rustc_middle::mir::interpret::{Pointer, Scalar, alloc_range};
use rustc_middle::mir::{self, ConstValue};
use rustc_middle::ty::Ty;
use rustc_middle::ty::layout::{LayoutOf, TyAndLayout};
use rustc_middle::{bug, span_bug};
use tracing::debug;
use super::place::{PlaceRef, PlaceValue};
@@ -352,79 +351,83 @@ impl<'a, 'tcx, V: CodegenObject> OperandRef<'tcx, V> {
pub(crate) fn extract_field<Bx: BuilderMethods<'a, 'tcx, Value = V>>(
&self,
fx: &mut FunctionCx<'a, 'tcx, Bx>,
bx: &mut Bx,
i: usize,
) -> Self {
let field = self.layout.field(bx.cx(), i);
let offset = self.layout.fields.offset(i);
let mut val = match (self.val, self.layout.backend_repr) {
// If the field is ZST, it has no data.
_ if field.is_zst() => OperandValue::ZeroSized,
// Newtype of a scalar, scalar pair or vector.
(OperandValue::Immediate(_) | OperandValue::Pair(..), _)
if field.size == self.layout.size =>
{
assert_eq!(offset.bytes(), 0);
self.val
let val = if field.is_zst() {
OperandValue::ZeroSized
} else if field.size == self.layout.size {
assert_eq!(offset.bytes(), 0);
if let Some(field_val) = fx.codegen_transmute_operand(bx, *self, field) {
field_val
} else {
// we have to go through memory for things like
// Newtype vector of array, e.g. #[repr(simd)] struct S([i32; 4]);
let place = PlaceRef::alloca(bx, field);
self.val.store(bx, place.val.with_type(self.layout));
bx.load_operand(place).val
}
// Extract a scalar component from a pair.
(OperandValue::Pair(a_llval, b_llval), BackendRepr::ScalarPair(a, b)) => {
if offset.bytes() == 0 {
assert_eq!(field.size, a.size(bx.cx()));
OperandValue::Immediate(a_llval)
} else {
assert_eq!(offset, a.size(bx.cx()).align_to(b.align(bx.cx()).abi));
assert_eq!(field.size, b.size(bx.cx()));
OperandValue::Immediate(b_llval)
} else {
let (in_scalar, imm) = match (self.val, self.layout.backend_repr) {
// Extract a scalar component from a pair.
(OperandValue::Pair(a_llval, b_llval), BackendRepr::ScalarPair(a, b)) => {
if offset.bytes() == 0 {
assert_eq!(field.size, a.size(bx.cx()));
(Some(a), a_llval)
} else {
assert_eq!(offset, a.size(bx.cx()).align_to(b.align(bx.cx()).abi));
assert_eq!(field.size, b.size(bx.cx()));
(Some(b), b_llval)
}
}
}
// `#[repr(simd)]` types are also immediate.
(OperandValue::Immediate(llval), BackendRepr::Vector { .. }) => {
OperandValue::Immediate(bx.extract_element(llval, bx.cx().const_usize(i as u64)))
}
// `#[repr(simd)]` types are also immediate.
(OperandValue::Immediate(llval), BackendRepr::Vector { .. }) => {
(None, bx.extract_element(llval, bx.cx().const_usize(i as u64)))
}
_ => bug!("OperandRef::extract_field({:?}): not applicable", self),
_ => {
span_bug!(fx.mir.span, "OperandRef::extract_field({:?}): not applicable", self)
}
};
OperandValue::Immediate(match field.backend_repr {
BackendRepr::Vector { .. } => imm,
BackendRepr::Scalar(out_scalar) => {
let Some(in_scalar) = in_scalar else {
span_bug!(
fx.mir.span,
"OperandRef::extract_field({:?}): missing input scalar for output scalar",
self
)
};
if in_scalar != out_scalar {
// If the backend and backend_immediate types might differ,
// flip back to the backend type then to the new immediate.
// This avoids nop truncations, but still handles things like
// Bools in union fields needs to be truncated.
let backend = bx.from_immediate(imm);
bx.to_immediate_scalar(backend, out_scalar)
} else {
imm
}
}
BackendRepr::Memory { sized: true } => {
span_bug!(
fx.mir.span,
"Projecting into a simd type with padding doesn't work; \
See <https://github.com/rust-lang/rust/issues/137108>",
);
}
BackendRepr::Uninhabited
| BackendRepr::ScalarPair(_, _)
| BackendRepr::Memory { sized: false } => bug!(),
})
};
match (&mut val, field.backend_repr) {
(OperandValue::ZeroSized, _) => {}
(
OperandValue::Immediate(llval),
BackendRepr::Scalar(_) | BackendRepr::ScalarPair(..) | BackendRepr::Vector { .. },
) => {
// Bools in union fields needs to be truncated.
*llval = bx.to_immediate(*llval, field);
}
(OperandValue::Pair(a, b), BackendRepr::ScalarPair(a_abi, b_abi)) => {
// Bools in union fields needs to be truncated.
*a = bx.to_immediate_scalar(*a, a_abi);
*b = bx.to_immediate_scalar(*b, b_abi);
}
// Newtype vector of array, e.g. #[repr(simd)] struct S([i32; 4]);
(OperandValue::Immediate(llval), BackendRepr::Memory { sized: true }) => {
assert_matches!(self.layout.backend_repr, BackendRepr::Vector { .. });
let llfield_ty = bx.cx().backend_type(field);
// Can't bitcast an aggregate, so round trip through memory.
let llptr = bx.alloca(field.size, field.align.abi);
bx.store(*llval, llptr, field.align.abi);
*llval = bx.load(llfield_ty, llptr, field.align.abi);
}
(
OperandValue::Immediate(_),
BackendRepr::Uninhabited | BackendRepr::Memory { sized: false },
) => {
bug!()
}
(OperandValue::Pair(..), _) => bug!(),
(OperandValue::Ref(..), _) => bug!(),
}
OperandRef { val, layout: field }
}
}
@@ -587,7 +590,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
"Bad PlaceRef: destructing pointers should use cast/PtrMetadata, \
but tried to access field {f:?} of pointer {o:?}",
);
o = o.extract_field(bx, f.index());
o = o.extract_field(self, bx, f.index());
}
mir::ProjectionElem::Index(_)
| mir::ProjectionElem::ConstantIndex { .. } => {