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Rollup merge of rust-lang#56312 - oli-obk:const_eval_literal, r=eddyb
Deduplicate literal -> constant lowering
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,102 @@ | ||
| 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<&'tcx 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::from_const_value(tcx, 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 })) | ||
| } |
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