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interpret: a bit of cast cleanup #103546

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Oct 26, 2022
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interpret: a bit of cast cleanup #103546

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61 changes: 30 additions & 31 deletions compiler/rustc_const_eval/src/interpret/cast.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -138,21 +138,19 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
Ok(())
}

/// Handles 'IntToInt' and 'IntToFloat' casts.
pub fn int_to_int_or_float(
&mut self,
src: &ImmTy<'tcx, M::Provenance>,
cast_ty: Ty<'tcx>,
) -> InterpResult<'tcx, Immediate<M::Provenance>> {
if (src.layout.ty.is_integral() || src.layout.ty.is_char() || src.layout.ty.is_bool())
&& (cast_ty.is_floating_point() || cast_ty.is_integral() || cast_ty.is_char())
{
let scalar = src.to_scalar();
Ok(self.cast_from_int_like(scalar, src.layout, cast_ty)?.into())
} else {
bug!("Unexpected cast from type {:?}", src.layout.ty)
}
assert!(src.layout.ty.is_integral() || src.layout.ty.is_char() || src.layout.ty.is_bool());
assert!(cast_ty.is_floating_point() || cast_ty.is_integral() || cast_ty.is_char());

Ok(self.cast_from_int_like(src.to_scalar(), src.layout, cast_ty)?.into())
}

/// Handles 'FloatToFloat' and 'FloatToInt' casts.
pub fn float_to_float_or_int(
&mut self,
src: &ImmTy<'tcx, M::Provenance>,
Expand Down Expand Up @@ -180,31 +178,29 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
src: &ImmTy<'tcx, M::Provenance>,
cast_ty: Ty<'tcx>,
) -> InterpResult<'tcx, Immediate<M::Provenance>> {
assert!(src.layout.ty.is_any_ptr());
assert!(cast_ty.is_unsafe_ptr());
// Handle casting any ptr to raw ptr (might be a fat ptr).
if src.layout.ty.is_any_ptr() && cast_ty.is_unsafe_ptr() {
let dest_layout = self.layout_of(cast_ty)?;
if dest_layout.size == src.layout.size {
// Thin or fat pointer that just hast the ptr kind of target type changed.
return Ok(**src);
} else {
// Casting the metadata away from a fat ptr.
assert_eq!(src.layout.size, 2 * self.pointer_size());
assert_eq!(dest_layout.size, self.pointer_size());
assert!(src.layout.ty.is_unsafe_ptr());
return match **src {
Immediate::ScalarPair(data, _) => Ok(data.into()),
Immediate::Scalar(..) => span_bug!(
self.cur_span(),
"{:?} input to a fat-to-thin cast ({:?} -> {:?})",
*src,
src.layout.ty,
cast_ty
),
Immediate::Uninit => throw_ub!(InvalidUninitBytes(None)),
};
}
let dest_layout = self.layout_of(cast_ty)?;
if dest_layout.size == src.layout.size {
// Thin or fat pointer that just hast the ptr kind of target type changed.
return Ok(**src);
} else {
bug!("Can't cast 'Ptr' or 'FnPtr' into {:?}", cast_ty);
// Casting the metadata away from a fat ptr.
assert_eq!(src.layout.size, 2 * self.pointer_size());
assert_eq!(dest_layout.size, self.pointer_size());
assert!(src.layout.ty.is_unsafe_ptr());
return match **src {
Immediate::ScalarPair(data, _) => Ok(data.into()),
Immediate::Scalar(..) => span_bug!(
self.cur_span(),
"{:?} input to a fat-to-thin cast ({:?} -> {:?})",
*src,
src.layout.ty,
cast_ty
),
Immediate::Uninit => throw_ub!(InvalidUninitBytes(None)),
};
}
}

Expand Down Expand Up @@ -243,6 +239,8 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
Ok(Scalar::from_maybe_pointer(ptr, self).into())
}

/// Low-level cast helper function. This works directly on scalars and can take 'int-like' input
/// type (basically everything with a scalar layout) to int/float/char types.
pub fn cast_from_int_like(
&self,
scalar: Scalar<M::Provenance>, // input value (there is no ScalarTy so we separate data+layout)
Expand Down Expand Up @@ -282,6 +280,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
})
}

/// Low-level cast helper function. Converts an apfloat `f` into int or float types.
fn cast_from_float<F>(&self, f: F, dest_ty: Ty<'tcx>) -> Scalar<M::Provenance>
where
F: Float + Into<Scalar<M::Provenance>> + FloatConvert<Single> + FloatConvert<Double>,
Expand Down