560 lines
23 KiB
Rust
560 lines
23 KiB
Rust
#![allow(clippy::float_cmp)]
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use crate::utils::{clip, higher, sext, unsext};
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use if_chain::if_chain;
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use rustc_ast::ast::{FloatTy, LitFloatType, LitKind};
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use rustc_data_structures::sync::Lrc;
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use rustc_hir::def::{DefKind, Res};
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use rustc_hir::{BinOp, BinOpKind, Block, Expr, ExprKind, HirId, QPath, UnOp};
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use rustc_lint::LateContext;
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use rustc_middle::ty::subst::{Subst, SubstsRef};
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use rustc_middle::ty::{self, Ty, TyCtxt};
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use rustc_middle::{bug, span_bug};
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use rustc_span::symbol::Symbol;
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use std::cmp::Ordering::{self, Equal};
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use std::convert::TryInto;
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use std::hash::{Hash, Hasher};
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/// A `LitKind`-like enum to fold constant `Expr`s into.
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#[derive(Debug, Clone)]
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pub enum Constant {
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/// A `String` (e.g., "abc").
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Str(String),
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/// A binary string (e.g., `b"abc"`).
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Binary(Lrc<Vec<u8>>),
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/// A single `char` (e.g., `'a'`).
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Char(char),
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/// An integer's bit representation.
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Int(u128),
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/// An `f32`.
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F32(f32),
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/// An `f64`.
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F64(f64),
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/// `true` or `false`.
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Bool(bool),
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/// An array of constants.
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Vec(Vec<Constant>),
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/// Also an array, but with only one constant, repeated N times.
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Repeat(Box<Constant>, u64),
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/// A tuple of constants.
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Tuple(Vec<Constant>),
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/// A raw pointer.
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RawPtr(u128),
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/// A literal with syntax error.
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Err(Symbol),
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}
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impl PartialEq for Constant {
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fn eq(&self, other: &Self) -> bool {
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match (self, other) {
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(&Self::Str(ref ls), &Self::Str(ref rs)) => ls == rs,
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(&Self::Binary(ref l), &Self::Binary(ref r)) => l == r,
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(&Self::Char(l), &Self::Char(r)) => l == r,
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(&Self::Int(l), &Self::Int(r)) => l == r,
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(&Self::F64(l), &Self::F64(r)) => {
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// We want `Fw32 == FwAny` and `FwAny == Fw64`, and by transitivity we must have
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// `Fw32 == Fw64`, so don’t compare them.
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// `to_bits` is required to catch non-matching 0.0, -0.0, and NaNs.
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l.to_bits() == r.to_bits()
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},
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(&Self::F32(l), &Self::F32(r)) => {
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// We want `Fw32 == FwAny` and `FwAny == Fw64`, and by transitivity we must have
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// `Fw32 == Fw64`, so don’t compare them.
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// `to_bits` is required to catch non-matching 0.0, -0.0, and NaNs.
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f64::from(l).to_bits() == f64::from(r).to_bits()
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},
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(&Self::Bool(l), &Self::Bool(r)) => l == r,
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(&Self::Vec(ref l), &Self::Vec(ref r)) | (&Self::Tuple(ref l), &Self::Tuple(ref r)) => l == r,
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(&Self::Repeat(ref lv, ref ls), &Self::Repeat(ref rv, ref rs)) => ls == rs && lv == rv,
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// TODO: are there inter-type equalities?
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_ => false,
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}
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}
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}
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impl Hash for Constant {
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fn hash<H>(&self, state: &mut H)
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where
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H: Hasher,
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{
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std::mem::discriminant(self).hash(state);
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match *self {
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Self::Str(ref s) => {
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s.hash(state);
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},
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Self::Binary(ref b) => {
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b.hash(state);
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},
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Self::Char(c) => {
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c.hash(state);
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},
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Self::Int(i) => {
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i.hash(state);
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},
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Self::F32(f) => {
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f64::from(f).to_bits().hash(state);
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},
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Self::F64(f) => {
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f.to_bits().hash(state);
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},
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Self::Bool(b) => {
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b.hash(state);
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},
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Self::Vec(ref v) | Self::Tuple(ref v) => {
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v.hash(state);
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},
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Self::Repeat(ref c, l) => {
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c.hash(state);
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l.hash(state);
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},
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Self::RawPtr(u) => {
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u.hash(state);
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},
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Self::Err(ref s) => {
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s.hash(state);
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},
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}
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}
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}
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impl Constant {
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pub fn partial_cmp(tcx: TyCtxt<'_>, cmp_type: Ty<'_>, left: &Self, right: &Self) -> Option<Ordering> {
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match (left, right) {
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(&Self::Str(ref ls), &Self::Str(ref rs)) => Some(ls.cmp(rs)),
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(&Self::Char(ref l), &Self::Char(ref r)) => Some(l.cmp(r)),
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(&Self::Int(l), &Self::Int(r)) => {
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if let ty::Int(int_ty) = cmp_type.kind {
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Some(sext(tcx, l, int_ty).cmp(&sext(tcx, r, int_ty)))
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} else {
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Some(l.cmp(&r))
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}
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},
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(&Self::F64(l), &Self::F64(r)) => l.partial_cmp(&r),
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(&Self::F32(l), &Self::F32(r)) => l.partial_cmp(&r),
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(&Self::Bool(ref l), &Self::Bool(ref r)) => Some(l.cmp(r)),
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(&Self::Tuple(ref l), &Self::Tuple(ref r)) | (&Self::Vec(ref l), &Self::Vec(ref r)) => l
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.iter()
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.zip(r.iter())
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.map(|(li, ri)| Self::partial_cmp(tcx, cmp_type, li, ri))
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.find(|r| r.map_or(true, |o| o != Ordering::Equal))
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.unwrap_or_else(|| Some(l.len().cmp(&r.len()))),
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(&Self::Repeat(ref lv, ref ls), &Self::Repeat(ref rv, ref rs)) => {
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match Self::partial_cmp(tcx, cmp_type, lv, rv) {
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Some(Equal) => Some(ls.cmp(rs)),
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x => x,
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}
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},
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// TODO: are there any useful inter-type orderings?
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_ => None,
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}
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}
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}
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/// Parses a `LitKind` to a `Constant`.
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pub fn lit_to_constant(lit: &LitKind, ty: Option<Ty<'_>>) -> Constant {
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match *lit {
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LitKind::Str(ref is, _) => Constant::Str(is.to_string()),
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LitKind::Byte(b) => Constant::Int(u128::from(b)),
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LitKind::ByteStr(ref s) => Constant::Binary(Lrc::clone(s)),
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LitKind::Char(c) => Constant::Char(c),
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LitKind::Int(n, _) => Constant::Int(n),
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LitKind::Float(ref is, LitFloatType::Suffixed(fty)) => match fty {
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FloatTy::F32 => Constant::F32(is.as_str().parse().unwrap()),
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FloatTy::F64 => Constant::F64(is.as_str().parse().unwrap()),
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},
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LitKind::Float(ref is, LitFloatType::Unsuffixed) => match ty.expect("type of float is known").kind {
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ty::Float(FloatTy::F32) => Constant::F32(is.as_str().parse().unwrap()),
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ty::Float(FloatTy::F64) => Constant::F64(is.as_str().parse().unwrap()),
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_ => bug!(),
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},
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LitKind::Bool(b) => Constant::Bool(b),
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LitKind::Err(s) => Constant::Err(s),
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}
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}
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pub fn constant<'c, 'cc>(
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lcx: &LateContext<'c, 'cc>,
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tables: &'c ty::TypeckTables<'cc>,
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e: &Expr<'_>,
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) -> Option<(Constant, bool)> {
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let mut cx = ConstEvalLateContext {
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lcx,
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tables,
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param_env: lcx.param_env,
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needed_resolution: false,
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substs: lcx.tcx.intern_substs(&[]),
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};
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cx.expr(e).map(|cst| (cst, cx.needed_resolution))
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}
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pub fn constant_simple<'c, 'cc>(
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lcx: &LateContext<'c, 'cc>,
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tables: &'c ty::TypeckTables<'cc>,
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e: &Expr<'_>,
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) -> Option<Constant> {
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constant(lcx, tables, e).and_then(|(cst, res)| if res { None } else { Some(cst) })
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}
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/// Creates a `ConstEvalLateContext` from the given `LateContext` and `TypeckTables`.
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pub fn constant_context<'c, 'cc>(
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lcx: &'c LateContext<'c, 'cc>,
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tables: &'c ty::TypeckTables<'cc>,
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) -> ConstEvalLateContext<'c, 'cc> {
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ConstEvalLateContext {
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lcx,
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tables,
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param_env: lcx.param_env,
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needed_resolution: false,
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substs: lcx.tcx.intern_substs(&[]),
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}
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}
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pub struct ConstEvalLateContext<'a, 'tcx> {
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lcx: &'a LateContext<'a, 'tcx>,
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tables: &'a ty::TypeckTables<'tcx>,
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param_env: ty::ParamEnv<'tcx>,
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needed_resolution: bool,
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substs: SubstsRef<'tcx>,
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}
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impl<'c, 'cc> ConstEvalLateContext<'c, 'cc> {
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/// Simple constant folding: Insert an expression, get a constant or none.
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pub fn expr(&mut self, e: &Expr<'_>) -> Option<Constant> {
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if let Some((ref cond, ref then, otherwise)) = higher::if_block(&e) {
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return self.ifthenelse(cond, then, otherwise);
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}
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match e.kind {
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ExprKind::Path(ref qpath) => self.fetch_path(qpath, e.hir_id, self.tables.expr_ty(e)),
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ExprKind::Block(ref block, _) => self.block(block),
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ExprKind::Lit(ref lit) => Some(lit_to_constant(&lit.node, self.tables.expr_ty_opt(e))),
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ExprKind::Array(ref vec) => self.multi(vec).map(Constant::Vec),
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ExprKind::Tup(ref tup) => self.multi(tup).map(Constant::Tuple),
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ExprKind::Repeat(ref value, _) => {
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let n = match self.tables.expr_ty(e).kind {
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ty::Array(_, n) => n.try_eval_usize(self.lcx.tcx, self.lcx.param_env)?,
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_ => span_bug!(e.span, "typeck error"),
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};
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self.expr(value).map(|v| Constant::Repeat(Box::new(v), n))
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},
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ExprKind::Unary(op, ref operand) => self.expr(operand).and_then(|o| match op {
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UnOp::UnNot => self.constant_not(&o, self.tables.expr_ty(e)),
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UnOp::UnNeg => self.constant_negate(&o, self.tables.expr_ty(e)),
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UnOp::UnDeref => Some(o),
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}),
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ExprKind::Binary(op, ref left, ref right) => self.binop(op, left, right),
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ExprKind::Call(ref callee, ref args) => {
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// We only handle a few const functions for now.
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if_chain! {
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if args.is_empty();
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if let ExprKind::Path(qpath) = &callee.kind;
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let res = self.tables.qpath_res(qpath, callee.hir_id);
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if let Some(def_id) = res.opt_def_id();
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let def_path: Vec<_> = self.lcx.get_def_path(def_id).into_iter().map(Symbol::as_str).collect();
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let def_path: Vec<&str> = def_path.iter().take(4).map(|s| &**s).collect();
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if let ["core", "num", int_impl, "max_value"] = *def_path;
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then {
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let value = match int_impl {
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"<impl i8>" => i8::max_value() as u128,
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"<impl i16>" => i16::max_value() as u128,
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"<impl i32>" => i32::max_value() as u128,
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"<impl i64>" => i64::max_value() as u128,
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"<impl i128>" => i128::max_value() as u128,
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_ => return None,
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};
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Some(Constant::Int(value))
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}
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else {
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None
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}
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}
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},
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ExprKind::Index(ref arr, ref index) => self.index(arr, index),
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// TODO: add other expressions.
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_ => None,
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}
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}
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#[allow(clippy::cast_possible_wrap)]
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fn constant_not(&self, o: &Constant, ty: Ty<'_>) -> Option<Constant> {
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use self::Constant::{Bool, Int};
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match *o {
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Bool(b) => Some(Bool(!b)),
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Int(value) => {
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let value = !value;
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match ty.kind {
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ty::Int(ity) => Some(Int(unsext(self.lcx.tcx, value as i128, ity))),
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ty::Uint(ity) => Some(Int(clip(self.lcx.tcx, value, ity))),
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_ => None,
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}
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},
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_ => None,
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}
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}
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fn constant_negate(&self, o: &Constant, ty: Ty<'_>) -> Option<Constant> {
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use self::Constant::{Int, F32, F64};
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match *o {
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Int(value) => {
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let ity = match ty.kind {
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ty::Int(ity) => ity,
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_ => return None,
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};
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// sign extend
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let value = sext(self.lcx.tcx, value, ity);
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let value = value.checked_neg()?;
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// clear unused bits
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Some(Int(unsext(self.lcx.tcx, value, ity)))
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},
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F32(f) => Some(F32(-f)),
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F64(f) => Some(F64(-f)),
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_ => None,
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}
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}
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/// Create `Some(Vec![..])` of all constants, unless there is any
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/// non-constant part.
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fn multi(&mut self, vec: &[Expr<'_>]) -> Option<Vec<Constant>> {
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vec.iter().map(|elem| self.expr(elem)).collect::<Option<_>>()
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}
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/// Lookup a possibly constant expression from a `ExprKind::Path`.
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fn fetch_path(&mut self, qpath: &QPath<'_>, id: HirId, ty: Ty<'cc>) -> Option<Constant> {
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let res = self.tables.qpath_res(qpath, id);
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match res {
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Res::Def(DefKind::Const | DefKind::AssocConst, def_id) => {
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let substs = self.tables.node_substs(id);
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let substs = if self.substs.is_empty() {
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substs
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} else {
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substs.subst(self.lcx.tcx, self.substs)
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};
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let result = self
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.lcx
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.tcx
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.const_eval_resolve(self.param_env, def_id, substs, None, None)
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.ok()
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.map(|val| rustc_middle::ty::Const::from_value(self.lcx.tcx, val, ty))?;
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let result = miri_to_const(&result);
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if result.is_some() {
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self.needed_resolution = true;
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}
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result
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},
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// FIXME: cover all usable cases.
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_ => None,
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}
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}
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fn index(&mut self, lhs: &'_ Expr<'_>, index: &'_ Expr<'_>) -> Option<Constant> {
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let lhs = self.expr(lhs);
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let index = self.expr(index);
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match (lhs, index) {
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(Some(Constant::Vec(vec)), Some(Constant::Int(index))) => match vec[index as usize] {
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Constant::F32(x) => Some(Constant::F32(x)),
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Constant::F64(x) => Some(Constant::F64(x)),
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_ => None,
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},
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(Some(Constant::Vec(vec)), _) => {
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if !vec.is_empty() && vec.iter().all(|x| *x == vec[0]) {
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match vec[0] {
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Constant::F32(x) => Some(Constant::F32(x)),
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Constant::F64(x) => Some(Constant::F64(x)),
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_ => None,
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}
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} else {
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None
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}
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},
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_ => None,
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}
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}
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/// A block can only yield a constant if it only has one constant expression.
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fn block(&mut self, block: &Block<'_>) -> Option<Constant> {
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if block.stmts.is_empty() {
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block.expr.as_ref().and_then(|b| self.expr(b))
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} else {
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None
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}
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}
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fn ifthenelse(&mut self, cond: &Expr<'_>, then: &Expr<'_>, otherwise: Option<&Expr<'_>>) -> Option<Constant> {
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if let Some(Constant::Bool(b)) = self.expr(cond) {
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if b {
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self.expr(&*then)
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} else {
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otherwise.as_ref().and_then(|expr| self.expr(expr))
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}
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} else {
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None
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}
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}
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fn binop(&mut self, op: BinOp, left: &Expr<'_>, right: &Expr<'_>) -> Option<Constant> {
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let l = self.expr(left)?;
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let r = self.expr(right);
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match (l, r) {
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(Constant::Int(l), Some(Constant::Int(r))) => match self.tables.expr_ty(left).kind {
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ty::Int(ity) => {
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let l = sext(self.lcx.tcx, l, ity);
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let r = sext(self.lcx.tcx, r, ity);
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let zext = |n: i128| Constant::Int(unsext(self.lcx.tcx, n, ity));
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match op.node {
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BinOpKind::Add => l.checked_add(r).map(zext),
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BinOpKind::Sub => l.checked_sub(r).map(zext),
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BinOpKind::Mul => l.checked_mul(r).map(zext),
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BinOpKind::Div if r != 0 => l.checked_div(r).map(zext),
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BinOpKind::Rem if r != 0 => l.checked_rem(r).map(zext),
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BinOpKind::Shr => l.checked_shr(r.try_into().expect("invalid shift")).map(zext),
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BinOpKind::Shl => l.checked_shl(r.try_into().expect("invalid shift")).map(zext),
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BinOpKind::BitXor => Some(zext(l ^ r)),
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BinOpKind::BitOr => Some(zext(l | r)),
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BinOpKind::BitAnd => Some(zext(l & r)),
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BinOpKind::Eq => Some(Constant::Bool(l == r)),
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BinOpKind::Ne => Some(Constant::Bool(l != r)),
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BinOpKind::Lt => Some(Constant::Bool(l < r)),
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BinOpKind::Le => Some(Constant::Bool(l <= r)),
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BinOpKind::Ge => Some(Constant::Bool(l >= r)),
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BinOpKind::Gt => Some(Constant::Bool(l > r)),
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_ => None,
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}
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},
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ty::Uint(_) => match op.node {
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BinOpKind::Add => l.checked_add(r).map(Constant::Int),
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BinOpKind::Sub => l.checked_sub(r).map(Constant::Int),
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BinOpKind::Mul => l.checked_mul(r).map(Constant::Int),
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BinOpKind::Div => l.checked_div(r).map(Constant::Int),
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BinOpKind::Rem => l.checked_rem(r).map(Constant::Int),
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BinOpKind::Shr => l.checked_shr(r.try_into().expect("shift too large")).map(Constant::Int),
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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(result: &ty::Const<'_>) -> Option<Constant> {
|
||
use rustc_middle::mir::interpret::{ConstValue, Scalar};
|
||
match result.val {
|
||
ty::ConstKind::Value(ConstValue::Scalar(Scalar::Raw { data: d, .. })) => match result.ty.kind {
|
||
ty::Bool => Some(Constant::Bool(d == 1)),
|
||
ty::Uint(_) | ty::Int(_) => Some(Constant::Int(d)),
|
||
ty::Float(FloatTy::F32) => Some(Constant::F32(f32::from_bits(
|
||
d.try_into().expect("invalid f32 bit representation"),
|
||
))),
|
||
ty::Float(FloatTy::F64) => Some(Constant::F64(f64::from_bits(
|
||
d.try_into().expect("invalid f64 bit representation"),
|
||
))),
|
||
ty::RawPtr(type_and_mut) => {
|
||
if let ty::Uint(_) = type_and_mut.ty.kind {
|
||
return Some(Constant::RawPtr(d));
|
||
}
|
||
None
|
||
},
|
||
// FIXME: implement other conversions.
|
||
_ => None,
|
||
},
|
||
ty::ConstKind::Value(ConstValue::Slice { data, start, end }) => match result.ty.kind {
|
||
ty::Ref(_, tam, _) => match tam.kind {
|
||
ty::Str => String::from_utf8(
|
||
data.inspect_with_undef_and_ptr_outside_interpreter(start..end)
|
||
.to_owned(),
|
||
)
|
||
.ok()
|
||
.map(Constant::Str),
|
||
_ => None,
|
||
},
|
||
_ => None,
|
||
},
|
||
ty::ConstKind::Value(ConstValue::ByRef { alloc, offset: _ }) => match result.ty.kind {
|
||
ty::Array(sub_type, len) => match sub_type.kind {
|
||
ty::Float(FloatTy::F32) => match miri_to_const(len) {
|
||
Some(Constant::Int(len)) => alloc
|
||
.inspect_with_undef_and_ptr_outside_interpreter(0..(4 * len as usize))
|
||
.to_owned()
|
||
.chunks(4)
|
||
.map(|chunk| {
|
||
Some(Constant::F32(f32::from_le_bytes(
|
||
chunk.try_into().expect("this shouldn't happen"),
|
||
)))
|
||
})
|
||
.collect::<Option<Vec<Constant>>>()
|
||
.map(Constant::Vec),
|
||
_ => None,
|
||
},
|
||
ty::Float(FloatTy::F64) => match miri_to_const(len) {
|
||
Some(Constant::Int(len)) => alloc
|
||
.inspect_with_undef_and_ptr_outside_interpreter(0..(8 * len as usize))
|
||
.to_owned()
|
||
.chunks(8)
|
||
.map(|chunk| {
|
||
Some(Constant::F64(f64::from_le_bytes(
|
||
chunk.try_into().expect("this shouldn't happen"),
|
||
)))
|
||
})
|
||
.collect::<Option<Vec<Constant>>>()
|
||
.map(Constant::Vec),
|
||
_ => None,
|
||
},
|
||
// FIXME: implement other array type conversions.
|
||
_ => None,
|
||
},
|
||
_ => None,
|
||
},
|
||
// FIXME: implement other conversions.
|
||
_ => None,
|
||
}
|
||
}
|