| #![allow(cast_possible_truncation)] |
| #![allow(float_cmp)] |
| |
| use rustc::lint::LateContext; |
| use rustc::hir::def::Def; |
| use rustc::hir::*; |
| use rustc::ty::{self, Ty, TyCtxt, Instance}; |
| use rustc::ty::subst::{Subst, Substs}; |
| use std::cmp::Ordering::{self, Equal}; |
| use std::cmp::PartialOrd; |
| use std::hash::{Hash, Hasher}; |
| use std::mem; |
| use std::rc::Rc; |
| use syntax::ast::{FloatTy, LitKind}; |
| use syntax::ptr::P; |
| use rustc::middle::const_val::ConstVal; |
| use utils::{sext, unsext, clip}; |
| |
| #[derive(Debug, Copy, Clone)] |
| pub enum FloatWidth { |
| F32, |
| F64, |
| Any, |
| } |
| |
| impl From<FloatTy> for FloatWidth { |
| fn from(ty: FloatTy) -> Self { |
| match ty { |
| FloatTy::F32 => FloatWidth::F32, |
| FloatTy::F64 => FloatWidth::F64, |
| } |
| } |
| } |
| |
| /// A `LitKind`-like enum to fold constant `Expr`s into. |
| #[derive(Debug, Clone)] |
| pub enum Constant { |
| /// a String "abc" |
| Str(String), |
| /// a Binary String b"abc" |
| Binary(Rc<Vec<u8>>), |
| /// a single char 'a' |
| Char(char), |
| /// an integer's bit representation |
| Int(u128), |
| /// an f32 |
| F32(f32), |
| /// an f64 |
| F64(f64), |
| /// true or false |
| Bool(bool), |
| /// an array of constants |
| Vec(Vec<Constant>), |
| /// also an array, but with only one constant, repeated N times |
| Repeat(Box<Constant>, u64), |
| /// a tuple of constants |
| Tuple(Vec<Constant>), |
| } |
| |
| impl PartialEq for Constant { |
| fn eq(&self, other: &Self) -> bool { |
| match (self, other) { |
| (&Constant::Str(ref ls), &Constant::Str(ref rs)) => ls == rs, |
| (&Constant::Binary(ref l), &Constant::Binary(ref r)) => l == r, |
| (&Constant::Char(l), &Constant::Char(r)) => l == r, |
| (&Constant::Int(l), &Constant::Int(r)) => l == r, |
| (&Constant::F64(l), &Constant::F64(r)) => { |
| // we want `Fw32 == FwAny` and `FwAny == Fw64`, by transitivity we must have |
| // `Fw32 == Fw64` so don’t compare them |
| // mem::transmute is required to catch non-matching 0.0, -0.0, and NaNs |
| unsafe { mem::transmute::<f64, u64>(l) == mem::transmute::<f64, u64>(r) } |
| }, |
| (&Constant::F32(l), &Constant::F32(r)) => { |
| // we want `Fw32 == FwAny` and `FwAny == Fw64`, by transitivity we must have |
| // `Fw32 == Fw64` so don’t compare them |
| // mem::transmute is required to catch non-matching 0.0, -0.0, and NaNs |
| unsafe { mem::transmute::<f64, u64>(f64::from(l)) == mem::transmute::<f64, u64>(f64::from(r)) } |
| }, |
| (&Constant::Bool(l), &Constant::Bool(r)) => l == r, |
| (&Constant::Vec(ref l), &Constant::Vec(ref r)) | (&Constant::Tuple(ref l), &Constant::Tuple(ref r)) => l == r, |
| (&Constant::Repeat(ref lv, ref ls), &Constant::Repeat(ref rv, ref rs)) => ls == rs && lv == rv, |
| _ => false, // TODO: Are there inter-type equalities? |
| } |
| } |
| } |
| |
| impl Hash for Constant { |
| fn hash<H>(&self, state: &mut H) |
| where |
| H: Hasher, |
| { |
| match *self { |
| Constant::Str(ref s) => { |
| s.hash(state); |
| }, |
| Constant::Binary(ref b) => { |
| b.hash(state); |
| }, |
| Constant::Char(c) => { |
| c.hash(state); |
| }, |
| Constant::Int(i) => { |
| i.hash(state); |
| }, |
| Constant::F32(f) => { |
| unsafe { mem::transmute::<f64, u64>(f64::from(f)) }.hash(state); |
| }, |
| Constant::F64(f) => { |
| unsafe { mem::transmute::<f64, u64>(f) }.hash(state); |
| }, |
| Constant::Bool(b) => { |
| b.hash(state); |
| }, |
| Constant::Vec(ref v) | Constant::Tuple(ref v) => { |
| v.hash(state); |
| }, |
| Constant::Repeat(ref c, l) => { |
| c.hash(state); |
| l.hash(state); |
| }, |
| } |
| } |
| } |
| |
| impl PartialOrd for Constant { |
| fn partial_cmp(&self, other: &Self) -> Option<Ordering> { |
| match (self, other) { |
| (&Constant::Str(ref ls), &Constant::Str(ref rs)) => Some(ls.cmp(rs)), |
| (&Constant::Char(ref l), &Constant::Char(ref r)) => Some(l.cmp(r)), |
| (&Constant::Int(l), &Constant::Int(r)) => Some(l.cmp(&r)), |
| (&Constant::F64(l), &Constant::F64(r)) => l.partial_cmp(&r), |
| (&Constant::F32(l), &Constant::F32(r)) => l.partial_cmp(&r), |
| (&Constant::Bool(ref l), &Constant::Bool(ref r)) => Some(l.cmp(r)), |
| (&Constant::Tuple(ref l), &Constant::Tuple(ref r)) | (&Constant::Vec(ref l), &Constant::Vec(ref r)) => { |
| l.partial_cmp(r) |
| }, |
| (&Constant::Repeat(ref lv, ref ls), &Constant::Repeat(ref rv, ref rs)) => match lv.partial_cmp(rv) { |
| Some(Equal) => Some(ls.cmp(rs)), |
| x => x, |
| }, |
| _ => None, // TODO: Are there any useful inter-type orderings? |
| } |
| } |
| } |
| |
| /// parse a `LitKind` to a `Constant` |
| pub fn lit_to_constant<'tcx>(lit: &LitKind, ty: Ty<'tcx>) -> Constant { |
| use syntax::ast::*; |
| |
| match *lit { |
| LitKind::Str(ref is, _) => Constant::Str(is.to_string()), |
| LitKind::Byte(b) => Constant::Int(u128::from(b)), |
| LitKind::ByteStr(ref s) => Constant::Binary(Rc::clone(s)), |
| LitKind::Char(c) => Constant::Char(c), |
| LitKind::Int(n, _) => Constant::Int(n), |
| LitKind::Float(ref is, _) | |
| LitKind::FloatUnsuffixed(ref is) => match ty.sty { |
| ty::TyFloat(FloatTy::F32) => Constant::F32(is.as_str().parse().unwrap()), |
| ty::TyFloat(FloatTy::F64) => Constant::F64(is.as_str().parse().unwrap()), |
| _ => bug!(), |
| }, |
| LitKind::Bool(b) => Constant::Bool(b), |
| } |
| } |
| |
| pub fn constant(lcx: &LateContext, e: &Expr) -> Option<(Constant, bool)> { |
| let mut cx = ConstEvalLateContext { |
| tcx: lcx.tcx, |
| tables: lcx.tables, |
| param_env: lcx.param_env, |
| needed_resolution: false, |
| substs: lcx.tcx.intern_substs(&[]), |
| }; |
| cx.expr(e).map(|cst| (cst, cx.needed_resolution)) |
| } |
| |
| pub fn constant_simple(lcx: &LateContext, e: &Expr) -> Option<Constant> { |
| constant(lcx, e).and_then(|(cst, res)| if res { None } else { Some(cst) }) |
| } |
| |
| /// Creates a `ConstEvalLateContext` from the given `LateContext` and `TypeckTables` |
| pub fn constant_context<'c, 'cc>(lcx: &LateContext<'c, 'cc>, tables: &'cc ty::TypeckTables<'cc>) -> ConstEvalLateContext<'c, 'cc> { |
| ConstEvalLateContext { |
| tcx: lcx.tcx, |
| tables, |
| param_env: lcx.param_env, |
| needed_resolution: false, |
| substs: lcx.tcx.intern_substs(&[]), |
| } |
| } |
| |
| pub struct ConstEvalLateContext<'a, 'tcx: 'a> { |
| tcx: TyCtxt<'a, 'tcx, 'tcx>, |
| tables: &'a ty::TypeckTables<'tcx>, |
| param_env: ty::ParamEnv<'tcx>, |
| needed_resolution: bool, |
| substs: &'tcx Substs<'tcx>, |
| } |
| |
| impl<'c, 'cc> ConstEvalLateContext<'c, 'cc> { |
| /// simple constant folding: Insert an expression, get a constant or none. |
| pub fn expr(&mut self, e: &Expr) -> Option<Constant> { |
| match e.node { |
| ExprPath(ref qpath) => self.fetch_path(qpath, e.hir_id), |
| ExprBlock(ref block) => self.block(block), |
| ExprIf(ref cond, ref then, ref otherwise) => self.ifthenelse(cond, then, otherwise), |
| ExprLit(ref lit) => Some(lit_to_constant(&lit.node, self.tables.expr_ty(e))), |
| ExprArray(ref vec) => self.multi(vec).map(Constant::Vec), |
| ExprTup(ref tup) => self.multi(tup).map(Constant::Tuple), |
| ExprRepeat(ref value, _) => { |
| let n = match self.tables.expr_ty(e).sty { |
| ty::TyArray(_, n) => n.assert_usize(self.tcx).expect("array length"), |
| _ => span_bug!(e.span, "typeck error"), |
| }; |
| self.expr(value).map(|v| Constant::Repeat(Box::new(v), n as u64)) |
| }, |
| ExprUnary(op, ref operand) => self.expr(operand).and_then(|o| match op { |
| UnNot => self.constant_not(&o, self.tables.expr_ty(e)), |
| UnNeg => self.constant_negate(&o, self.tables.expr_ty(e)), |
| UnDeref => Some(o), |
| }), |
| ExprBinary(op, ref left, ref right) => self.binop(op, left, right), |
| // TODO: add other expressions |
| _ => None, |
| } |
| } |
| |
| fn constant_not(&self, o: &Constant, ty: ty::Ty) -> Option<Constant> { |
| use self::Constant::*; |
| match *o { |
| Bool(b) => Some(Bool(!b)), |
| Int(value) => { |
| let mut value = !value; |
| match ty.sty { |
| ty::TyInt(ity) => Some(Int(unsext(self.tcx, value as i128, ity))), |
| ty::TyUint(ity) => Some(Int(clip(self.tcx, value, ity))), |
| _ => None, |
| } |
| }, |
| _ => None, |
| } |
| } |
| |
| fn constant_negate(&self, o: &Constant, ty: ty::Ty) -> Option<Constant> { |
| use self::Constant::*; |
| match *o { |
| Int(value) => { |
| let ity = match ty.sty { |
| ty::TyInt(ity) => ity, |
| _ => return None, |
| }; |
| // sign extend |
| let value = sext(self.tcx, value, ity); |
| let value = value.checked_neg()?; |
| // clear unused bits |
| Some(Int(unsext(self.tcx, value, ity))) |
| }, |
| F32(f) => Some(F32(-f)), |
| F64(f) => Some(F64(-f)), |
| _ => None, |
| } |
| } |
| |
| /// create `Some(Vec![..])` of all constants, unless there is any |
| /// non-constant part |
| fn multi(&mut self, vec: &[Expr]) -> Option<Vec<Constant>> { |
| vec.iter() |
| .map(|elem| self.expr(elem)) |
| .collect::<Option<_>>() |
| } |
| |
| /// lookup a possibly constant expression from a ExprPath |
| fn fetch_path(&mut self, qpath: &QPath, id: HirId) -> Option<Constant> { |
| let def = self.tables.qpath_def(qpath, id); |
| match def { |
| Def::Const(def_id) | Def::AssociatedConst(def_id) => { |
| let substs = self.tables.node_substs(id); |
| let substs = if self.substs.is_empty() { |
| substs |
| } else { |
| substs.subst(self.tcx, self.substs) |
| }; |
| let instance = Instance::resolve(self.tcx, self.param_env, def_id, substs)?; |
| let gid = GlobalId { |
| instance, |
| promoted: None, |
| }; |
| use rustc::mir::interpret::GlobalId; |
| let result = self.tcx.const_eval(self.param_env.and(gid)).ok()?; |
| let ret = miri_to_const(self.tcx, result); |
| if ret.is_some() { |
| self.needed_resolution = true; |
| } |
| return ret; |
| }, |
| _ => {}, |
| } |
| None |
| } |
| |
| /// A block can only yield a constant if it only has one constant expression |
| fn block(&mut self, block: &Block) -> Option<Constant> { |
| if block.stmts.is_empty() { |
| block.expr.as_ref().and_then(|b| self.expr(b)) |
| } else { |
| None |
| } |
| } |
| |
| fn ifthenelse(&mut self, cond: &Expr, then: &P<Expr>, otherwise: &Option<P<Expr>>) -> Option<Constant> { |
| if let Some(Constant::Bool(b)) = self.expr(cond) { |
| if b { |
| self.expr(&**then) |
| } else { |
| otherwise.as_ref().and_then(|expr| self.expr(expr)) |
| } |
| } else { |
| None |
| } |
| } |
| |
| fn binop(&mut self, op: BinOp, left: &Expr, right: &Expr) -> Option<Constant> { |
| let l = self.expr(left)?; |
| let r = self.expr(right); |
| match (l, r) { |
| (Constant::Int(l), Some(Constant::Int(r))) => { |
| match self.tables.expr_ty(left).sty { |
| ty::TyInt(ity) => { |
| let l = sext(self.tcx, l, ity); |
| let r = sext(self.tcx, r, ity); |
| let zext = |n: i128| Constant::Int(unsext(self.tcx, n, ity)); |
| match op.node { |
| BiAdd => l.checked_add(r).map(zext), |
| BiSub => l.checked_sub(r).map(zext), |
| BiMul => l.checked_mul(r).map(zext), |
| BiDiv if r != 0 => l.checked_div(r).map(zext), |
| BiRem if r != 0 => l.checked_rem(r).map(zext), |
| BiShr => l.checked_shr(r as u128 as u32).map(zext), |
| BiShl => l.checked_shl(r as u128 as u32).map(zext), |
| BiBitXor => Some(zext(l ^ r)), |
| BiBitOr => Some(zext(l | r)), |
| BiBitAnd => Some(zext(l & r)), |
| BiEq => Some(Constant::Bool(l == r)), |
| BiNe => Some(Constant::Bool(l != r)), |
| BiLt => Some(Constant::Bool(l < r)), |
| BiLe => Some(Constant::Bool(l <= r)), |
| BiGe => Some(Constant::Bool(l >= r)), |
| BiGt => Some(Constant::Bool(l > r)), |
| _ => None, |
| } |
| } |
| ty::TyUint(_) => { |
| match op.node { |
| BiAdd => l.checked_add(r).map(Constant::Int), |
| BiSub => l.checked_sub(r).map(Constant::Int), |
| BiMul => l.checked_mul(r).map(Constant::Int), |
| BiDiv => l.checked_div(r).map(Constant::Int), |
| BiRem => l.checked_rem(r).map(Constant::Int), |
| BiShr => l.checked_shr(r as u32).map(Constant::Int), |
| BiShl => l.checked_shl(r as u32).map(Constant::Int), |
| BiBitXor => Some(Constant::Int(l ^ r)), |
| BiBitOr => Some(Constant::Int(l | r)), |
| BiBitAnd => Some(Constant::Int(l & r)), |
| BiEq => Some(Constant::Bool(l == r)), |
| BiNe => Some(Constant::Bool(l != r)), |
| BiLt => Some(Constant::Bool(l < r)), |
| BiLe => Some(Constant::Bool(l <= r)), |
| BiGe => Some(Constant::Bool(l >= r)), |
| BiGt => Some(Constant::Bool(l > r)), |
| _ => None, |
| } |
| }, |
| _ => None, |
| } |
| }, |
| (Constant::F32(l), Some(Constant::F32(r))) => match op.node { |
| BiAdd => Some(Constant::F32(l + r)), |
| BiSub => Some(Constant::F32(l - r)), |
| BiMul => Some(Constant::F32(l * r)), |
| BiDiv => Some(Constant::F32(l / r)), |
| BiRem => Some(Constant::F32(l % r)), |
| BiEq => Some(Constant::Bool(l == r)), |
| BiNe => Some(Constant::Bool(l != r)), |
| BiLt => Some(Constant::Bool(l < r)), |
| BiLe => Some(Constant::Bool(l <= r)), |
| BiGe => Some(Constant::Bool(l >= r)), |
| BiGt => Some(Constant::Bool(l > r)), |
| _ => None, |
| }, |
| (Constant::F64(l), Some(Constant::F64(r))) => match op.node { |
| BiAdd => Some(Constant::F64(l + r)), |
| BiSub => Some(Constant::F64(l - r)), |
| BiMul => Some(Constant::F64(l * r)), |
| BiDiv => Some(Constant::F64(l / r)), |
| BiRem => Some(Constant::F64(l % r)), |
| BiEq => Some(Constant::Bool(l == r)), |
| BiNe => Some(Constant::Bool(l != r)), |
| BiLt => Some(Constant::Bool(l < r)), |
| BiLe => Some(Constant::Bool(l <= r)), |
| BiGe => Some(Constant::Bool(l >= r)), |
| BiGt => Some(Constant::Bool(l > r)), |
| _ => None, |
| }, |
| (l, r) => match (op.node, l, r) { |
| (BiAnd, Constant::Bool(false), _) => Some(Constant::Bool(false)), |
| (BiOr, Constant::Bool(true), _) => Some(Constant::Bool(true)), |
| (BiAnd, Constant::Bool(true), Some(r)) | (BiOr, Constant::Bool(false), Some(r)) => Some(r), |
| (BiBitXor, Constant::Bool(l), Some(Constant::Bool(r))) => Some(Constant::Bool(l ^ r)), |
| (BiBitAnd, Constant::Bool(l), Some(Constant::Bool(r))) => Some(Constant::Bool(l & r)), |
| (BiBitOr, Constant::Bool(l), Some(Constant::Bool(r))) => Some(Constant::Bool(l | r)), |
| _ => None, |
| }, |
| } |
| } |
| } |
| |
| pub fn miri_to_const<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, result: &ty::Const<'tcx>) -> Option<Constant> { |
| use rustc::mir::interpret::{PrimVal, ConstValue}; |
| match result.val { |
| ConstVal::Value(ConstValue::ByVal(PrimVal::Bytes(b))) => match result.ty.sty { |
| ty::TyBool => Some(Constant::Bool(b == 1)), |
| ty::TyUint(_) | ty::TyInt(_) => Some(Constant::Int(b)), |
| ty::TyFloat(FloatTy::F32) => Some(Constant::F32(f32::from_bits(b as u32))), |
| ty::TyFloat(FloatTy::F64) => Some(Constant::F64(f64::from_bits(b as u64))), |
| // FIXME: implement other conversion |
| _ => None, |
| }, |
| ConstVal::Value(ConstValue::ByValPair(PrimVal::Ptr(ptr), PrimVal::Bytes(n))) => match result.ty.sty { |
| ty::TyRef(_, tam, _) => match tam.sty { |
| ty::TyStr => { |
| let alloc = tcx |
| .interpret_interner |
| .get_alloc(ptr.alloc_id) |
| .unwrap(); |
| let offset = ptr.offset as usize; |
| let n = n as usize; |
| String::from_utf8(alloc.bytes[offset..(offset + n)].to_owned()).ok().map(Constant::Str) |
| }, |
| _ => None, |
| }, |
| _ => None, |
| } |
| // FIXME: implement other conversions |
| _ => None, |
| } |
| } |
