| #![allow(clippy::float_cmp)] |
| |
| use crate::utils::{clip, get_def_path, sext, unsext}; |
| use if_chain::if_chain; |
| use rustc::hir::def::Def; |
| use rustc::hir::*; |
| use rustc::lint::LateContext; |
| use rustc::ty::subst::{Subst, SubstsRef}; |
| use rustc::ty::{self, Instance, Ty, TyCtxt}; |
| use rustc::{bug, span_bug}; |
| use rustc_data_structures::sync::Lrc; |
| use std::cmp::Ordering::{self, Equal}; |
| use std::cmp::PartialOrd; |
| use std::convert::TryFrom; |
| use std::convert::TryInto; |
| use std::hash::{Hash, Hasher}; |
| use syntax::ast::{FloatTy, LitKind}; |
| use syntax::ptr::P; |
| use syntax_pos::symbol::Symbol; |
| |
| /// A `LitKind`-like enum to fold constant `Expr`s into. |
| #[derive(Debug, Clone)] |
| pub enum Constant { |
| /// A `String` (e.g., "abc"). |
| Str(String), |
| /// A binary string (e.g., `b"abc"`). |
| Binary(Lrc<Vec<u8>>), |
| /// A single `char` (e.g., `'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>), |
| /// A raw pointer. |
| RawPtr(u128), |
| /// A literal with syntax error. |
| Err(Symbol), |
| } |
| |
| 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`, and by transitivity we must have |
| // `Fw32 == Fw64`, so don’t compare them. |
| // `to_bits` is required to catch non-matching 0.0, -0.0, and NaNs. |
| l.to_bits() == r.to_bits() |
| }, |
| (&Constant::F32(l), &Constant::F32(r)) => { |
| // We want `Fw32 == FwAny` and `FwAny == Fw64`, and by transitivity we must have |
| // `Fw32 == Fw64`, so don’t compare them. |
| // `to_bits` is required to catch non-matching 0.0, -0.0, and NaNs. |
| f64::from(l).to_bits() == f64::from(r).to_bits() |
| }, |
| (&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, |
| // TODO: are there inter-type equalities? |
| _ => false, |
| } |
| } |
| } |
| |
| 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) => { |
| f64::from(f).to_bits().hash(state); |
| }, |
| Constant::F64(f) => { |
| f.to_bits().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); |
| }, |
| Constant::RawPtr(u) => { |
| u.hash(state); |
| }, |
| Constant::Err(ref s) => { |
| s.hash(state); |
| }, |
| } |
| } |
| } |
| |
| impl Constant { |
| pub fn partial_cmp(tcx: TyCtxt<'_, '_, '_>, cmp_type: Ty<'_>, left: &Self, right: &Self) -> Option<Ordering> { |
| match (left, right) { |
| (&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)) => { |
| if let ty::Int(int_ty) = cmp_type.sty { |
| Some(sext(tcx, l, int_ty).cmp(&sext(tcx, r, int_ty))) |
| } else { |
| 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 |
| .iter() |
| .zip(r.iter()) |
| .map(|(li, ri)| Self::partial_cmp(tcx, cmp_type, li, ri)) |
| .find(|r| r.map_or(true, |o| o != Ordering::Equal)) |
| .unwrap_or_else(|| Some(l.len().cmp(&r.len()))), |
| (&Constant::Repeat(ref lv, ref ls), &Constant::Repeat(ref rv, ref rs)) => { |
| match Self::partial_cmp(tcx, cmp_type, lv, rv) { |
| Some(Equal) => Some(ls.cmp(rs)), |
| x => x, |
| } |
| }, |
| // TODO: are there any useful inter-type orderings? |
| _ => None, |
| } |
| } |
| } |
| |
| /// Parses 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(Lrc::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::Float(FloatTy::F32) => Constant::F32(is.as_str().parse().unwrap()), |
| ty::Float(FloatTy::F64) => Constant::F64(is.as_str().parse().unwrap()), |
| _ => bug!(), |
| }, |
| LitKind::Bool(b) => Constant::Bool(b), |
| LitKind::Err(s) => Constant::Err(s), |
| } |
| } |
| |
| pub fn constant<'c, 'cc>( |
| lcx: &LateContext<'c, 'cc>, |
| tables: &'c ty::TypeckTables<'cc>, |
| e: &Expr, |
| ) -> Option<(Constant, bool)> { |
| let mut cx = ConstEvalLateContext { |
| tcx: lcx.tcx, |
| 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<'c, 'cc>( |
| lcx: &LateContext<'c, 'cc>, |
| tables: &'c ty::TypeckTables<'cc>, |
| e: &Expr, |
| ) -> Option<Constant> { |
| constant(lcx, tables, 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: &'c 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: SubstsRef<'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 { |
| ExprKind::Path(ref qpath) => self.fetch_path(qpath, e.hir_id), |
| ExprKind::Block(ref block, _) => self.block(block), |
| ExprKind::If(ref cond, ref then, ref otherwise) => self.ifthenelse(cond, then, otherwise), |
| ExprKind::Lit(ref lit) => Some(lit_to_constant(&lit.node, self.tables.expr_ty(e))), |
| ExprKind::Array(ref vec) => self.multi(vec).map(Constant::Vec), |
| ExprKind::Tup(ref tup) => self.multi(tup).map(Constant::Tuple), |
| ExprKind::Repeat(ref value, _) => { |
| let n = match self.tables.expr_ty(e).sty { |
| ty::Array(_, 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)) |
| }, |
| ExprKind::Unary(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), |
| }), |
| ExprKind::Binary(op, ref left, ref right) => self.binop(op, left, right), |
| ExprKind::Call(ref callee, ref args) => { |
| // We only handle a few const functions for now. |
| if_chain! { |
| if args.is_empty(); |
| if let ExprKind::Path(qpath) = &callee.node; |
| let def = self.tables.qpath_def(qpath, callee.hir_id); |
| if let Some(def_id) = def.opt_def_id(); |
| let def_path = get_def_path(self.tcx, def_id); |
| if let &["core", "num", impl_ty, "max_value"] = &def_path[..]; |
| then { |
| let value = match impl_ty { |
| "<impl i8>" => i8::max_value() as u128, |
| "<impl i16>" => i16::max_value() as u128, |
| "<impl i32>" => i32::max_value() as u128, |
| "<impl i64>" => i64::max_value() as u128, |
| "<impl i128>" => i128::max_value() as u128, |
| _ => return None, |
| }; |
| Some(Constant::Int(value)) |
| } |
| else { |
| None |
| } |
| } |
| }, |
| // TODO: add other expressions. |
| _ => None, |
| } |
| } |
| |
| #[allow(clippy::cast_possible_wrap)] |
| fn constant_not(&self, o: &Constant, ty: Ty<'_>) -> Option<Constant> { |
| use self::Constant::*; |
| match *o { |
| Bool(b) => Some(Bool(!b)), |
| Int(value) => { |
| let value = !value; |
| match ty.sty { |
| ty::Int(ity) => Some(Int(unsext(self.tcx, value as i128, ity))), |
| ty::Uint(ity) => Some(Int(clip(self.tcx, value, ity))), |
| _ => None, |
| } |
| }, |
| _ => None, |
| } |
| } |
| |
| fn constant_negate(&self, o: &Constant, ty: Ty<'_>) -> Option<Constant> { |
| use self::Constant::*; |
| match *o { |
| Int(value) => { |
| let ity = match ty.sty { |
| ty::Int(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 ExprKind::Path. |
| fn fetch_path(&mut self, qpath: &QPath, id: HirId) -> Option<Constant> { |
| use rustc::mir::interpret::GlobalId; |
| |
| 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, |
| }; |
| |
| 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; |
| } |
| ret |
| }, |
| // FIXME: cover all useable cases. |
| _ => 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::Int(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 { |
| BinOpKind::Add => l.checked_add(r).map(zext), |
| BinOpKind::Sub => l.checked_sub(r).map(zext), |
| BinOpKind::Mul => l.checked_mul(r).map(zext), |
| BinOpKind::Div if r != 0 => l.checked_div(r).map(zext), |
| BinOpKind::Rem if r != 0 => l.checked_rem(r).map(zext), |
| BinOpKind::Shr => l.checked_shr(r.try_into().expect("invalid shift")).map(zext), |
| BinOpKind::Shl => l.checked_shl(r.try_into().expect("invalid shift")).map(zext), |
| BinOpKind::BitXor => Some(zext(l ^ r)), |
| BinOpKind::BitOr => Some(zext(l | r)), |
| BinOpKind::BitAnd => Some(zext(l & r)), |
| BinOpKind::Eq => Some(Constant::Bool(l == r)), |
| BinOpKind::Ne => Some(Constant::Bool(l != r)), |
| BinOpKind::Lt => Some(Constant::Bool(l < r)), |
| BinOpKind::Le => Some(Constant::Bool(l <= r)), |
| BinOpKind::Ge => Some(Constant::Bool(l >= r)), |
| BinOpKind::Gt => Some(Constant::Bool(l > r)), |
| _ => None, |
| } |
| }, |
| ty::Uint(_) => match op.node { |
| BinOpKind::Add => l.checked_add(r).map(Constant::Int), |
| BinOpKind::Sub => l.checked_sub(r).map(Constant::Int), |
| BinOpKind::Mul => l.checked_mul(r).map(Constant::Int), |
| BinOpKind::Div => l.checked_div(r).map(Constant::Int), |
| BinOpKind::Rem => l.checked_rem(r).map(Constant::Int), |
| BinOpKind::Shr => l.checked_shr(r.try_into().expect("shift too large")).map(Constant::Int), |
| BinOpKind::Shl => l.checked_shl(r.try_into().expect("shift too large")).map(Constant::Int), |
| BinOpKind::BitXor => Some(Constant::Int(l ^ r)), |
| BinOpKind::BitOr => Some(Constant::Int(l | r)), |
| BinOpKind::BitAnd => Some(Constant::Int(l & r)), |
| BinOpKind::Eq => Some(Constant::Bool(l == r)), |
| BinOpKind::Ne => Some(Constant::Bool(l != r)), |
| BinOpKind::Lt => Some(Constant::Bool(l < r)), |
| BinOpKind::Le => Some(Constant::Bool(l <= r)), |
| BinOpKind::Ge => Some(Constant::Bool(l >= r)), |
| BinOpKind::Gt => Some(Constant::Bool(l > r)), |
| _ => None, |
| }, |
| _ => None, |
| }, |
| (Constant::F32(l), Some(Constant::F32(r))) => match op.node { |
| BinOpKind::Add => Some(Constant::F32(l + r)), |
| BinOpKind::Sub => Some(Constant::F32(l - r)), |
| BinOpKind::Mul => Some(Constant::F32(l * r)), |
| BinOpKind::Div => Some(Constant::F32(l / r)), |
| BinOpKind::Rem => Some(Constant::F32(l % r)), |
| BinOpKind::Eq => Some(Constant::Bool(l == r)), |
| BinOpKind::Ne => Some(Constant::Bool(l != r)), |
| BinOpKind::Lt => Some(Constant::Bool(l < r)), |
| BinOpKind::Le => Some(Constant::Bool(l <= r)), |
| BinOpKind::Ge => Some(Constant::Bool(l >= r)), |
| BinOpKind::Gt => Some(Constant::Bool(l > r)), |
| _ => None, |
| }, |
| (Constant::F64(l), Some(Constant::F64(r))) => match op.node { |
| BinOpKind::Add => Some(Constant::F64(l + r)), |
| BinOpKind::Sub => Some(Constant::F64(l - r)), |
| BinOpKind::Mul => Some(Constant::F64(l * r)), |
| BinOpKind::Div => Some(Constant::F64(l / r)), |
| BinOpKind::Rem => Some(Constant::F64(l % r)), |
| BinOpKind::Eq => Some(Constant::Bool(l == r)), |
| BinOpKind::Ne => Some(Constant::Bool(l != r)), |
| BinOpKind::Lt => Some(Constant::Bool(l < r)), |
| BinOpKind::Le => Some(Constant::Bool(l <= r)), |
| BinOpKind::Ge => Some(Constant::Bool(l >= r)), |
| BinOpKind::Gt => Some(Constant::Bool(l > r)), |
| _ => None, |
| }, |
| (l, r) => match (op.node, l, r) { |
| (BinOpKind::And, Constant::Bool(false), _) => Some(Constant::Bool(false)), |
| (BinOpKind::Or, Constant::Bool(true), _) => Some(Constant::Bool(true)), |
| (BinOpKind::And, Constant::Bool(true), Some(r)) | (BinOpKind::Or, Constant::Bool(false), Some(r)) => { |
| Some(r) |
| }, |
| (BinOpKind::BitXor, Constant::Bool(l), Some(Constant::Bool(r))) => Some(Constant::Bool(l ^ r)), |
| (BinOpKind::BitAnd, Constant::Bool(l), Some(Constant::Bool(r))) => Some(Constant::Bool(l & r)), |
| (BinOpKind::BitOr, 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::{ConstValue, Scalar}; |
| match result.val { |
| ConstValue::Scalar(Scalar::Bits { bits: b, .. }) => match result.ty.sty { |
| ty::Bool => Some(Constant::Bool(b == 1)), |
| ty::Uint(_) | ty::Int(_) => Some(Constant::Int(b)), |
| ty::Float(FloatTy::F32) => Some(Constant::F32(f32::from_bits( |
| b.try_into().expect("invalid f32 bit representation"), |
| ))), |
| ty::Float(FloatTy::F64) => Some(Constant::F64(f64::from_bits( |
| b.try_into().expect("invalid f64 bit representation"), |
| ))), |
| ty::RawPtr(type_and_mut) => { |
| if let ty::Uint(_) = type_and_mut.ty.sty { |
| return Some(Constant::RawPtr(b)); |
| } |
| None |
| }, |
| // FIXME: implement other conversions. |
| _ => None, |
| }, |
| ConstValue::Slice(Scalar::Ptr(ptr), n) => match result.ty.sty { |
| ty::Ref(_, tam, _) => match tam.sty { |
| ty::Str => { |
| let alloc = tcx.alloc_map.lock().unwrap_memory(ptr.alloc_id); |
| let offset = ptr.offset.bytes().try_into().expect("too-large pointer offset"); |
| let n = usize::try_from(n).unwrap(); |
| String::from_utf8(alloc.bytes[offset..(offset + n)].to_owned()) |
| .ok() |
| .map(Constant::Str) |
| }, |
| _ => None, |
| }, |
| _ => None, |
| }, |
| // FIXME: implement other conversions. |
| _ => None, |
| } |
| } |
