| use syntax::ast; |
| use rustc::ty::{self, Ty, TyCtxt, ParamEnv}; |
| use syntax_pos::symbol::Symbol; |
| use rustc::mir::interpret::{ConstValue, Scalar}; |
| |
| #[derive(PartialEq)] |
| crate enum LitToConstError { |
| UnparseableFloat, |
| Reported, |
| } |
| |
| crate fn lit_to_const<'a, 'gcx, 'tcx>( |
| lit: &'tcx ast::LitKind, |
| tcx: TyCtxt<'a, 'gcx, 'tcx>, |
| ty: Ty<'tcx>, |
| neg: bool, |
| ) -> Result<ty::Const<'tcx>, LitToConstError> { |
| use syntax::ast::*; |
| |
| let trunc = |n| { |
| let param_ty = ParamEnv::reveal_all().and(tcx.lift_to_global(&ty).unwrap()); |
| 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 shift = 128 - width.bits(); |
| let result = (n << shift) >> shift; |
| trace!("trunc result: {}", result); |
| Ok(ConstValue::Scalar(Scalar::Bits { |
| bits: result, |
| size: width.bytes() as u8, |
| })) |
| }; |
| |
| use rustc::mir::interpret::*; |
| let lit = match *lit { |
| LitKind::Str(ref s, _) => { |
| let s = s.as_str(); |
| let id = tcx.allocate_bytes(s.as_bytes()); |
| ConstValue::new_slice(Scalar::Ptr(id.into()), s.len() as u64, &tcx) |
| }, |
| LitKind::ByteStr(ref data) => { |
| let id = tcx.allocate_bytes(data); |
| ConstValue::Scalar(Scalar::Ptr(id.into())) |
| }, |
| LitKind::Byte(n) => ConstValue::Scalar(Scalar::Bits { |
| bits: n as u128, |
| size: 1, |
| }), |
| LitKind::Int(n, _) if neg => { |
| let n = n as i128; |
| let n = n.overflowing_neg().0; |
| trunc(n as u128)? |
| }, |
| LitKind::Int(n, _) => trunc(n)?, |
| LitKind::Float(n, fty) => { |
| parse_float(n, fty, neg).map_err(|_| LitToConstError::UnparseableFloat)? |
| } |
| LitKind::FloatUnsuffixed(n) => { |
| let fty = match ty.sty { |
| ty::Float(fty) => fty, |
| _ => bug!() |
| }; |
| parse_float(n, fty, neg).map_err(|_| LitToConstError::UnparseableFloat)? |
| } |
| LitKind::Bool(b) => ConstValue::Scalar(Scalar::from_bool(b)), |
| LitKind::Char(c) => ConstValue::Scalar(Scalar::from_char(c)), |
| }; |
| Ok(ty::Const { val: lit, ty }) |
| } |
| |
| fn parse_float<'tcx>( |
| num: Symbol, |
| fty: ast::FloatTy, |
| neg: bool, |
| ) -> Result<ConstValue<'tcx>, ()> { |
| let num = num.as_str(); |
| use rustc_apfloat::ieee::{Single, Double}; |
| use rustc_apfloat::Float; |
| let (bits, size) = match fty { |
| ast::FloatTy::F32 => { |
| num.parse::<f32>().map_err(|_| ())?; |
| let mut f = num.parse::<Single>().unwrap_or_else(|e| { |
| panic!("apfloat::ieee::Single failed to parse `{}`: {:?}", num, e) |
| }); |
| if neg { |
| f = -f; |
| } |
| (f.to_bits(), 4) |
| } |
| ast::FloatTy::F64 => { |
| num.parse::<f64>().map_err(|_| ())?; |
| let mut f = num.parse::<Double>().unwrap_or_else(|e| { |
| panic!("apfloat::ieee::Single failed to parse `{}`: {:?}", num, e) |
| }); |
| if neg { |
| f = -f; |
| } |
| (f.to_bits(), 8) |
| } |
| }; |
| |
| Ok(ConstValue::Scalar(Scalar::Bits { bits, size })) |
| } |