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|
use rustc_apfloat::Float;
use rustc_ast as ast;
use rustc_middle::mir::interpret::{
Allocation, ConstValue, LitToConstError, LitToConstInput, Scalar,
};
use rustc_middle::ty::{self, ParamEnv, TyCtxt};
use rustc_span::symbol::Symbol;
use rustc_target::abi::Size;
crate fn lit_to_const<'tcx>(
tcx: TyCtxt<'tcx>,
lit_input: LitToConstInput<'tcx>,
) -> Result<&'tcx ty::Const<'tcx>, LitToConstError> {
let LitToConstInput { lit, ty, neg } = lit_input;
let trunc = |n| {
let param_ty = ParamEnv::reveal_all().and(ty);
let width = tcx.layout_of(param_ty).map_err(|_| LitToConstError::Reported)?.size;
trace!("trunc {} with size {} and shift {}", n, width.bits(), 128 - width.bits());
let result = width.truncate(n);
trace!("trunc result: {}", result);
Ok(ConstValue::Scalar(Scalar::from_uint(result, width)))
};
let lit = match (lit, &ty.kind()) {
(ast::LitKind::Str(s, _), ty::Ref(_, inner_ty, _)) if inner_ty.is_str() => {
let s = s.as_str();
let allocation = Allocation::from_byte_aligned_bytes(s.as_bytes());
let allocation = tcx.intern_const_alloc(allocation);
ConstValue::Slice { data: allocation, start: 0, end: s.len() }
}
(ast::LitKind::ByteStr(data), ty::Ref(_, inner_ty, _))
if matches!(inner_ty.kind(), ty::Slice(_)) =>
{
let allocation = Allocation::from_byte_aligned_bytes(data as &[u8]);
let allocation = tcx.intern_const_alloc(allocation);
ConstValue::Slice { data: allocation, start: 0, end: data.len() }
}
(ast::LitKind::ByteStr(data), ty::Ref(_, inner_ty, _)) if inner_ty.is_array() => {
let id = tcx.allocate_bytes(data);
ConstValue::Scalar(Scalar::Ptr(id.into()))
}
(ast::LitKind::Byte(n), ty::Uint(ty::UintTy::U8)) => {
ConstValue::Scalar(Scalar::from_uint(*n, Size::from_bytes(1)))
}
(ast::LitKind::Int(n, _), ty::Uint(_)) | (ast::LitKind::Int(n, _), ty::Int(_)) => {
trunc(if neg { (*n as i128).overflowing_neg().0 as u128 } else { *n })?
}
(ast::LitKind::Float(n, _), ty::Float(fty)) => {
parse_float(*n, *fty, neg).map_err(|_| LitToConstError::UnparseableFloat)?
}
(ast::LitKind::Bool(b), ty::Bool) => ConstValue::Scalar(Scalar::from_bool(*b)),
(ast::LitKind::Char(c), ty::Char) => ConstValue::Scalar(Scalar::from_char(*c)),
(ast::LitKind::Err(_), _) => return Err(LitToConstError::Reported),
_ => return Err(LitToConstError::TypeError),
};
Ok(ty::Const::from_value(tcx, lit, ty))
}
fn parse_float<'tcx>(num: Symbol, fty: ty::FloatTy, neg: bool) -> Result<ConstValue<'tcx>, ()> {
let num = num.as_str();
use rustc_apfloat::ieee::{Double, Single};
let scalar = match fty {
ty::FloatTy::F32 => {
let rust_f = num.parse::<f32>().map_err(|_| ())?;
let mut f = num.parse::<Single>().unwrap_or_else(|e| {
panic!("apfloat::ieee::Single failed to parse `{}`: {:?}", num, e)
});
assert!(
u128::from(rust_f.to_bits()) == f.to_bits(),
"apfloat::ieee::Single gave different result for `{}`: \
{}({:#x}) vs Rust's {}({:#x})",
rust_f,
f,
f.to_bits(),
Single::from_bits(rust_f.to_bits().into()),
rust_f.to_bits()
);
if neg {
f = -f;
}
Scalar::from_f32(f)
}
ty::FloatTy::F64 => {
let rust_f = num.parse::<f64>().map_err(|_| ())?;
let mut f = num.parse::<Double>().unwrap_or_else(|e| {
panic!("apfloat::ieee::Double failed to parse `{}`: {:?}", num, e)
});
assert!(
u128::from(rust_f.to_bits()) == f.to_bits(),
"apfloat::ieee::Double gave different result for `{}`: \
{}({:#x}) vs Rust's {}({:#x})",
rust_f,
f,
f.to_bits(),
Double::from_bits(rust_f.to_bits().into()),
rust_f.to_bits()
);
if neg {
f = -f;
}
Scalar::from_f64(f)
}
};
Ok(ConstValue::Scalar(scalar))
}
|
