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Propagate ScalarPair for any type.

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This commit is contained in:
Camille GILLOT 2023-02-08 21:05:56 +00:00
parent 895e2159f8
commit ccfa9af29d
5 changed files with 29 additions and 41 deletions
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48
compiler/rustc_mir_transform/src/const_prop.rs
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@ -581,40 +581,22 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
Some(self.operand_from_scalar(scalar, value.layout.ty))
}
Immediate::ScalarPair(..) => {
// Found a value represented as a pair. For now only do const-prop if the type
// of `rvalue` is also a tuple with two scalars.
// FIXME: enable the general case stated above ^.
let ty = value.layout.ty;
// Only do it for tuples
let ty::Tuple(types) = ty.kind() else { return None };
// Only do it if tuple is also a pair with two scalars
if let [ty1, ty2] = types[..] {
let ty_is_scalar = |ty| {
self.ecx.layout_of(ty).ok().map(|layout| layout.abi.is_scalar())
== Some(true)
};
let alloc = if ty_is_scalar(ty1) && ty_is_scalar(ty2) {
self.ecx
.intern_with_temp_alloc(value.layout, |ecx, dest| {
ecx.write_immediate(*imm, dest)
})
.unwrap()
} else {
return None;
};
let alloc = self
.ecx
.intern_with_temp_alloc(value.layout, |ecx, dest| {
ecx.write_immediate(*imm, dest)
})
.ok()?;
// Assign entire constant in a single statement.
// We can't use aggregates, as we run after the aggregate-lowering `MirPhase`.
let const_val = ConstValue::ByRef { alloc, offset: Size::ZERO };
let literal = ConstantKind::Val(const_val, ty);
Some(Operand::Constant(Box::new(Constant {
span: DUMMY_SP,
user_ty: None,
literal,
})))
} else {
None
}
let literal = ConstantKind::Val(
ConstValue::ByRef { alloc, offset: Size::ZERO },
value.layout.ty,
);
Some(Operand::Constant(Box::new(Constant {
span: DUMMY_SP,
user_ty: None,
literal,
})))
}
// Scalars or scalar pairs that contain undef values are assumed to not have
// successfully evaluated and are thus not propagated.