637 lines
24 KiB
Rust
637 lines
24 KiB
Rust
// Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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#![allow(non_camel_case_types)]
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#![allow(unsigned_negation)]
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pub use self::const_val::*;
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pub use self::constness::*;
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use metadata::csearch;
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use middle::{astencode, def};
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use middle::pat_util::def_to_path;
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use middle::ty::{self};
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use middle::astconv_util::{ast_ty_to_prim_ty};
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use util::nodemap::DefIdMap;
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use syntax::ast::{self, Expr};
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use syntax::parse::token::InternedString;
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use syntax::ptr::P;
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use syntax::visit::{self, Visitor};
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use syntax::{ast_map, ast_util, codemap};
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use std::collections::hash_map::Entry::Vacant;
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use std::rc::Rc;
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//
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// This pass classifies expressions by their constant-ness.
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//
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// Constant-ness comes in 3 flavours:
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//
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// - Integer-constants: can be evaluated by the frontend all the way down
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// to their actual value. They are used in a few places (enum
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// discriminants, switch arms) and are a subset of
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// general-constants. They cover all the integer and integer-ish
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// literals (nil, bool, int, uint, char, iNN, uNN) and all integer
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// operators and copies applied to them.
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//
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// - General-constants: can be evaluated by LLVM but not necessarily by
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// the frontend; usually due to reliance on target-specific stuff such
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// as "where in memory the value goes" or "what floating point mode the
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// target uses". This _includes_ integer-constants, plus the following
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// constructors:
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//
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// fixed-size vectors and strings: [] and ""/_
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// vector and string slices: &[] and &""
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// tuples: (,)
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// enums: foo(...)
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// floating point literals and operators
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// & and * pointers
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// copies of general constants
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//
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// (in theory, probably not at first: if/match on integer-const
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// conditions / discriminants)
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//
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// - Non-constants: everything else.
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//
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#[derive(Copy)]
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pub enum constness {
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integral_const,
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general_const,
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non_const
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}
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type constness_cache = DefIdMap<constness>;
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pub fn join(a: constness, b: constness) -> constness {
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match (a, b) {
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(integral_const, integral_const) => integral_const,
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(integral_const, general_const)
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| (general_const, integral_const)
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| (general_const, general_const) => general_const,
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_ => non_const
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}
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}
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pub fn join_all<It: Iterator<Item=constness>>(cs: It) -> constness {
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cs.fold(integral_const, |a, b| join(a, b))
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}
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fn lookup_const<'a>(tcx: &'a ty::ctxt, e: &Expr) -> Option<&'a Expr> {
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let opt_def = tcx.def_map.borrow().get(&e.id).cloned();
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match opt_def {
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Some(def::DefConst(def_id)) => {
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lookup_const_by_id(tcx, def_id)
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}
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Some(def::DefVariant(enum_def, variant_def, _)) => {
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lookup_variant_by_id(tcx, enum_def, variant_def)
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}
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_ => None
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}
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}
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fn lookup_variant_by_id<'a>(tcx: &'a ty::ctxt,
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enum_def: ast::DefId,
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variant_def: ast::DefId)
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-> Option<&'a Expr> {
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fn variant_expr<'a>(variants: &'a [P<ast::Variant>], id: ast::NodeId)
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-> Option<&'a Expr> {
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for variant in variants.iter() {
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if variant.node.id == id {
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return variant.node.disr_expr.as_ref().map(|e| &**e);
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}
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}
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None
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}
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if ast_util::is_local(enum_def) {
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match tcx.map.find(enum_def.node) {
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None => None,
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Some(ast_map::NodeItem(it)) => match it.node {
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ast::ItemEnum(ast::EnumDef { ref variants }, _) => {
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variant_expr(&variants[], variant_def.node)
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}
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_ => None
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},
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Some(_) => None
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}
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} else {
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match tcx.extern_const_variants.borrow().get(&variant_def) {
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Some(&ast::DUMMY_NODE_ID) => return None,
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Some(&expr_id) => {
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return Some(tcx.map.expect_expr(expr_id));
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}
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None => {}
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}
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let expr_id = match csearch::maybe_get_item_ast(tcx, enum_def,
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box |a, b, c, d| astencode::decode_inlined_item(a, b, c, d)) {
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csearch::found(&ast::IIItem(ref item)) => match item.node {
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ast::ItemEnum(ast::EnumDef { ref variants }, _) => {
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// NOTE this doesn't do the right thing, it compares inlined
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// NodeId's to the original variant_def's NodeId, but they
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// come from different crates, so they will likely never match.
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variant_expr(&variants[], variant_def.node).map(|e| e.id)
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}
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_ => None
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},
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_ => None
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};
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tcx.extern_const_variants.borrow_mut().insert(variant_def,
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expr_id.unwrap_or(ast::DUMMY_NODE_ID));
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expr_id.map(|id| tcx.map.expect_expr(id))
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}
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}
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pub fn lookup_const_by_id<'a>(tcx: &'a ty::ctxt, def_id: ast::DefId)
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-> Option<&'a Expr> {
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if ast_util::is_local(def_id) {
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match tcx.map.find(def_id.node) {
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None => None,
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Some(ast_map::NodeItem(it)) => match it.node {
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ast::ItemConst(_, ref const_expr) => {
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Some(&**const_expr)
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}
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_ => None
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},
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Some(_) => None
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}
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} else {
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match tcx.extern_const_statics.borrow().get(&def_id) {
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Some(&ast::DUMMY_NODE_ID) => return None,
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Some(&expr_id) => {
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return Some(tcx.map.expect_expr(expr_id));
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}
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None => {}
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}
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let expr_id = match csearch::maybe_get_item_ast(tcx, def_id,
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box |a, b, c, d| astencode::decode_inlined_item(a, b, c, d)) {
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csearch::found(&ast::IIItem(ref item)) => match item.node {
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ast::ItemConst(_, ref const_expr) => Some(const_expr.id),
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_ => None
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},
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_ => None
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};
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tcx.extern_const_statics.borrow_mut().insert(def_id,
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expr_id.unwrap_or(ast::DUMMY_NODE_ID));
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expr_id.map(|id| tcx.map.expect_expr(id))
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}
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}
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struct ConstEvalVisitor<'a, 'tcx: 'a> {
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tcx: &'a ty::ctxt<'tcx>,
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ccache: constness_cache,
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}
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impl<'a, 'tcx> ConstEvalVisitor<'a, 'tcx> {
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fn classify(&mut self, e: &Expr) -> constness {
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let did = ast_util::local_def(e.id);
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match self.ccache.get(&did) {
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Some(&x) => return x,
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None => {}
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}
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let cn = match e.node {
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ast::ExprLit(ref lit) => {
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match lit.node {
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ast::LitStr(..) | ast::LitFloat(..) => general_const,
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_ => integral_const
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}
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}
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ast::ExprUnary(_, ref inner) | ast::ExprParen(ref inner) =>
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self.classify(&**inner),
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ast::ExprBinary(_, ref a, ref b) =>
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join(self.classify(&**a), self.classify(&**b)),
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ast::ExprTup(ref es) |
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ast::ExprVec(ref es) =>
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join_all(es.iter().map(|e| self.classify(&**e))),
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ast::ExprStruct(_, ref fs, None) => {
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let cs = fs.iter().map(|f| self.classify(&*f.expr));
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join_all(cs)
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}
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ast::ExprCast(ref base, _) => {
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let ty = ty::expr_ty(self.tcx, e);
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let base = self.classify(&**base);
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if ty::type_is_integral(ty) {
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join(integral_const, base)
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} else if ty::type_is_fp(ty) {
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join(general_const, base)
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} else {
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non_const
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}
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}
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ast::ExprField(ref base, _) => self.classify(&**base),
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ast::ExprTupField(ref base, _) => self.classify(&**base),
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ast::ExprIndex(ref base, ref idx) =>
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join(self.classify(&**base), self.classify(&**idx)),
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ast::ExprAddrOf(ast::MutImmutable, ref base) =>
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self.classify(&**base),
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// FIXME: (#3728) we can probably do something CCI-ish
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// surrounding nonlocal constants. But we don't yet.
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ast::ExprPath(_) | ast::ExprQPath(_) => self.lookup_constness(e),
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ast::ExprRepeat(..) => general_const,
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ast::ExprBlock(ref block) => {
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match block.expr {
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Some(ref e) => self.classify(&**e),
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None => integral_const
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}
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}
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_ => non_const
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};
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self.ccache.insert(did, cn);
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cn
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}
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fn lookup_constness(&self, e: &Expr) -> constness {
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match lookup_const(self.tcx, e) {
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Some(rhs) => {
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let ty = ty::expr_ty(self.tcx, &*rhs);
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if ty::type_is_integral(ty) {
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integral_const
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} else {
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general_const
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}
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}
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None => non_const
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}
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}
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}
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impl<'a, 'tcx, 'v> Visitor<'v> for ConstEvalVisitor<'a, 'tcx> {
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fn visit_expr_post(&mut self, e: &Expr) {
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self.classify(e);
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}
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}
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pub fn process_crate(tcx: &ty::ctxt) {
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visit::walk_crate(&mut ConstEvalVisitor {
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tcx: tcx,
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ccache: DefIdMap(),
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}, tcx.map.krate());
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tcx.sess.abort_if_errors();
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}
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// FIXME (#33): this doesn't handle big integer/float literals correctly
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// (nor does the rest of our literal handling).
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#[derive(Clone, PartialEq)]
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pub enum const_val {
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const_float(f64),
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const_int(i64),
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const_uint(u64),
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const_str(InternedString),
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const_binary(Rc<Vec<u8> >),
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const_bool(bool)
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}
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pub fn const_expr_to_pat(tcx: &ty::ctxt, expr: &Expr) -> P<ast::Pat> {
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let pat = match expr.node {
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ast::ExprTup(ref exprs) =>
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ast::PatTup(exprs.iter().map(|expr| const_expr_to_pat(tcx, &**expr)).collect()),
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ast::ExprCall(ref callee, ref args) => {
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let def = tcx.def_map.borrow()[callee.id].clone();
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if let Vacant(entry) = tcx.def_map.borrow_mut().entry(expr.id) {
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entry.insert(def);
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}
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let path = match def {
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def::DefStruct(def_id) => def_to_path(tcx, def_id),
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def::DefVariant(_, variant_did, _) => def_to_path(tcx, variant_did),
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_ => unreachable!()
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};
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let pats = args.iter().map(|expr| const_expr_to_pat(tcx, &**expr)).collect();
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ast::PatEnum(path, Some(pats))
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}
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ast::ExprStruct(ref path, ref fields, None) => {
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let field_pats = fields.iter().map(|field| codemap::Spanned {
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span: codemap::DUMMY_SP,
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node: ast::FieldPat {
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ident: field.ident.node,
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pat: const_expr_to_pat(tcx, &*field.expr),
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is_shorthand: false,
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},
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}).collect();
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ast::PatStruct(path.clone(), field_pats, false)
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}
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ast::ExprVec(ref exprs) => {
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let pats = exprs.iter().map(|expr| const_expr_to_pat(tcx, &**expr)).collect();
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ast::PatVec(pats, None, vec![])
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}
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ast::ExprPath(ref path) => {
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let opt_def = tcx.def_map.borrow().get(&expr.id).cloned();
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match opt_def {
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Some(def::DefStruct(..)) =>
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ast::PatStruct(path.clone(), vec![], false),
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Some(def::DefVariant(..)) =>
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ast::PatEnum(path.clone(), None),
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_ => {
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match lookup_const(tcx, expr) {
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Some(actual) => return const_expr_to_pat(tcx, actual),
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_ => unreachable!()
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}
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}
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}
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}
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ast::ExprQPath(_) => {
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match lookup_const(tcx, expr) {
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Some(actual) => return const_expr_to_pat(tcx, actual),
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_ => unreachable!()
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}
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}
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_ => ast::PatLit(P(expr.clone()))
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};
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P(ast::Pat { id: expr.id, node: pat, span: expr.span })
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}
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pub fn eval_const_expr(tcx: &ty::ctxt, e: &Expr) -> const_val {
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match eval_const_expr_partial(tcx, e) {
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Ok(r) => r,
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Err(s) => tcx.sess.span_fatal(e.span, &s[])
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}
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}
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pub fn eval_const_expr_partial(tcx: &ty::ctxt, e: &Expr) -> Result<const_val, String> {
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fn fromb(b: bool) -> Result<const_val, String> { Ok(const_int(b as i64)) }
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match e.node {
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ast::ExprUnary(ast::UnNeg, ref inner) => {
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match eval_const_expr_partial(tcx, &**inner) {
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Ok(const_float(f)) => Ok(const_float(-f)),
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Ok(const_int(i)) => Ok(const_int(-i)),
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Ok(const_uint(i)) => Ok(const_uint(-i)),
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Ok(const_str(_)) => Err("negate on string".to_string()),
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Ok(const_bool(_)) => Err("negate on boolean".to_string()),
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ref err => ((*err).clone())
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}
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}
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ast::ExprUnary(ast::UnNot, ref inner) => {
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match eval_const_expr_partial(tcx, &**inner) {
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Ok(const_int(i)) => Ok(const_int(!i)),
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Ok(const_uint(i)) => Ok(const_uint(!i)),
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Ok(const_bool(b)) => Ok(const_bool(!b)),
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_ => Err("not on float or string".to_string())
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}
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}
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ast::ExprBinary(op, ref a, ref b) => {
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match (eval_const_expr_partial(tcx, &**a),
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eval_const_expr_partial(tcx, &**b)) {
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(Ok(const_float(a)), Ok(const_float(b))) => {
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match op.node {
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ast::BiAdd => Ok(const_float(a + b)),
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ast::BiSub => Ok(const_float(a - b)),
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ast::BiMul => Ok(const_float(a * b)),
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ast::BiDiv => Ok(const_float(a / b)),
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ast::BiRem => Ok(const_float(a % b)),
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ast::BiEq => fromb(a == b),
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ast::BiLt => fromb(a < b),
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ast::BiLe => fromb(a <= b),
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ast::BiNe => fromb(a != b),
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ast::BiGe => fromb(a >= b),
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ast::BiGt => fromb(a > b),
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_ => Err("can't do this op on floats".to_string())
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}
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}
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(Ok(const_int(a)), Ok(const_int(b))) => {
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match op.node {
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ast::BiAdd => Ok(const_int(a + b)),
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ast::BiSub => Ok(const_int(a - b)),
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ast::BiMul => Ok(const_int(a * b)),
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ast::BiDiv if b == 0 => {
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Err("attempted to divide by zero".to_string())
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}
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ast::BiDiv => Ok(const_int(a / b)),
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ast::BiRem if b == 0 => {
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Err("attempted remainder with a divisor of \
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zero".to_string())
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}
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ast::BiRem => Ok(const_int(a % b)),
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ast::BiAnd | ast::BiBitAnd => Ok(const_int(a & b)),
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ast::BiOr | ast::BiBitOr => Ok(const_int(a | b)),
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ast::BiBitXor => Ok(const_int(a ^ b)),
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ast::BiShl => Ok(const_int(a << b as uint)),
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ast::BiShr => Ok(const_int(a >> b as uint)),
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ast::BiEq => fromb(a == b),
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ast::BiLt => fromb(a < b),
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ast::BiLe => fromb(a <= b),
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ast::BiNe => fromb(a != b),
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ast::BiGe => fromb(a >= b),
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ast::BiGt => fromb(a > b)
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}
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}
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(Ok(const_uint(a)), Ok(const_uint(b))) => {
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match op.node {
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ast::BiAdd => Ok(const_uint(a + b)),
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ast::BiSub => Ok(const_uint(a - b)),
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ast::BiMul => Ok(const_uint(a * b)),
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ast::BiDiv if b == 0 => {
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Err("attempted to divide by zero".to_string())
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}
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ast::BiDiv => Ok(const_uint(a / b)),
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ast::BiRem if b == 0 => {
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Err("attempted remainder with a divisor of \
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zero".to_string())
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}
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ast::BiRem => Ok(const_uint(a % b)),
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ast::BiAnd | ast::BiBitAnd => Ok(const_uint(a & b)),
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ast::BiOr | ast::BiBitOr => Ok(const_uint(a | b)),
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ast::BiBitXor => Ok(const_uint(a ^ b)),
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ast::BiShl => Ok(const_uint(a << b as uint)),
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ast::BiShr => Ok(const_uint(a >> b as uint)),
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ast::BiEq => fromb(a == b),
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ast::BiLt => fromb(a < b),
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ast::BiLe => fromb(a <= b),
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ast::BiNe => fromb(a != b),
|
|
ast::BiGe => fromb(a >= b),
|
|
ast::BiGt => fromb(a > b),
|
|
}
|
|
}
|
|
// shifts can have any integral type as their rhs
|
|
(Ok(const_int(a)), Ok(const_uint(b))) => {
|
|
match op.node {
|
|
ast::BiShl => Ok(const_int(a << b as uint)),
|
|
ast::BiShr => Ok(const_int(a >> b as uint)),
|
|
_ => Err("can't do this op on an int and uint".to_string())
|
|
}
|
|
}
|
|
(Ok(const_uint(a)), Ok(const_int(b))) => {
|
|
match op.node {
|
|
ast::BiShl => Ok(const_uint(a << b as uint)),
|
|
ast::BiShr => Ok(const_uint(a >> b as uint)),
|
|
_ => Err("can't do this op on a uint and int".to_string())
|
|
}
|
|
}
|
|
(Ok(const_bool(a)), Ok(const_bool(b))) => {
|
|
Ok(const_bool(match op.node {
|
|
ast::BiAnd => a && b,
|
|
ast::BiOr => a || b,
|
|
ast::BiBitXor => a ^ b,
|
|
ast::BiBitAnd => a & b,
|
|
ast::BiBitOr => a | b,
|
|
ast::BiEq => a == b,
|
|
ast::BiNe => a != b,
|
|
_ => return Err("can't do this op on bools".to_string())
|
|
}))
|
|
}
|
|
_ => Err("bad operands for binary".to_string())
|
|
}
|
|
}
|
|
ast::ExprCast(ref base, ref target_ty) => {
|
|
// This tends to get called w/o the type actually having been
|
|
// populated in the ctxt, which was causing things to blow up
|
|
// (#5900). Fall back to doing a limited lookup to get past it.
|
|
let ety = ty::expr_ty_opt(tcx, e)
|
|
.or_else(|| ast_ty_to_prim_ty(tcx, &**target_ty))
|
|
.unwrap_or_else(|| {
|
|
tcx.sess.span_fatal(target_ty.span,
|
|
"target type not found for const cast")
|
|
});
|
|
|
|
macro_rules! define_casts {
|
|
($val:ident, {
|
|
$($ty_pat:pat => (
|
|
$intermediate_ty:ty,
|
|
$const_type:ident,
|
|
$target_ty:ty
|
|
)),*
|
|
}) => (match ety.sty {
|
|
$($ty_pat => {
|
|
match $val {
|
|
const_bool(b) => Ok($const_type(b as $intermediate_ty as $target_ty)),
|
|
const_uint(u) => Ok($const_type(u as $intermediate_ty as $target_ty)),
|
|
const_int(i) => Ok($const_type(i as $intermediate_ty as $target_ty)),
|
|
const_float(f) => Ok($const_type(f as $intermediate_ty as $target_ty)),
|
|
_ => Err(concat!(
|
|
"can't cast this type to ", stringify!($const_type)
|
|
).to_string())
|
|
}
|
|
},)*
|
|
_ => Err("can't cast this type".to_string())
|
|
})
|
|
}
|
|
|
|
eval_const_expr_partial(tcx, &**base)
|
|
.and_then(|val| define_casts!(val, {
|
|
ty::ty_int(ast::TyIs(_)) => (int, const_int, i64),
|
|
ty::ty_int(ast::TyI8) => (i8, const_int, i64),
|
|
ty::ty_int(ast::TyI16) => (i16, const_int, i64),
|
|
ty::ty_int(ast::TyI32) => (i32, const_int, i64),
|
|
ty::ty_int(ast::TyI64) => (i64, const_int, i64),
|
|
ty::ty_uint(ast::TyUs(_)) => (uint, const_uint, u64),
|
|
ty::ty_uint(ast::TyU8) => (u8, const_uint, u64),
|
|
ty::ty_uint(ast::TyU16) => (u16, const_uint, u64),
|
|
ty::ty_uint(ast::TyU32) => (u32, const_uint, u64),
|
|
ty::ty_uint(ast::TyU64) => (u64, const_uint, u64),
|
|
ty::ty_float(ast::TyF32) => (f32, const_float, f64),
|
|
ty::ty_float(ast::TyF64) => (f64, const_float, f64)
|
|
}))
|
|
}
|
|
ast::ExprPath(_) | ast::ExprQPath(_) => {
|
|
match lookup_const(tcx, e) {
|
|
Some(actual_e) => eval_const_expr_partial(tcx, &*actual_e),
|
|
None => Err("non-constant path in constant expr".to_string())
|
|
}
|
|
}
|
|
ast::ExprLit(ref lit) => Ok(lit_to_const(&**lit)),
|
|
ast::ExprParen(ref e) => eval_const_expr_partial(tcx, &**e),
|
|
ast::ExprBlock(ref block) => {
|
|
match block.expr {
|
|
Some(ref expr) => eval_const_expr_partial(tcx, &**expr),
|
|
None => Ok(const_int(0i64))
|
|
}
|
|
}
|
|
ast::ExprTupField(ref base, index) => {
|
|
// Get the base tuple if it is constant
|
|
if let Some(&ast::ExprTup(ref fields)) = lookup_const(tcx, &**base).map(|s| &s.node) {
|
|
// Check that the given index is within bounds and evaluate its value
|
|
if fields.len() > index.node {
|
|
return eval_const_expr_partial(tcx, &*fields[index.node])
|
|
} else {
|
|
return Err("tuple index out of bounds".to_string())
|
|
}
|
|
}
|
|
|
|
Err("non-constant struct in constant expr".to_string())
|
|
}
|
|
ast::ExprField(ref base, field_name) => {
|
|
// Get the base expression if it is a struct and it is constant
|
|
if let Some(&ast::ExprStruct(_, ref fields, _)) = lookup_const(tcx, &**base)
|
|
.map(|s| &s.node) {
|
|
// Check that the given field exists and evaluate it
|
|
if let Some(f) = fields.iter().find(|f|
|
|
f.ident.node.as_str() == field_name.node.as_str()) {
|
|
return eval_const_expr_partial(tcx, &*f.expr)
|
|
} else {
|
|
return Err("nonexistent struct field".to_string())
|
|
}
|
|
}
|
|
|
|
Err("non-constant struct in constant expr".to_string())
|
|
}
|
|
_ => Err("unsupported constant expr".to_string())
|
|
}
|
|
}
|
|
|
|
pub fn lit_to_const(lit: &ast::Lit) -> const_val {
|
|
match lit.node {
|
|
ast::LitStr(ref s, _) => const_str((*s).clone()),
|
|
ast::LitBinary(ref data) => {
|
|
const_binary(Rc::new(data.iter().map(|x| *x).collect()))
|
|
}
|
|
ast::LitByte(n) => const_uint(n as u64),
|
|
ast::LitChar(n) => const_uint(n as u64),
|
|
ast::LitInt(n, ast::SignedIntLit(_, ast::Plus)) |
|
|
ast::LitInt(n, ast::UnsuffixedIntLit(ast::Plus)) => const_int(n as i64),
|
|
ast::LitInt(n, ast::SignedIntLit(_, ast::Minus)) |
|
|
ast::LitInt(n, ast::UnsuffixedIntLit(ast::Minus)) => const_int(-(n as i64)),
|
|
ast::LitInt(n, ast::UnsignedIntLit(_)) => const_uint(n),
|
|
ast::LitFloat(ref n, _) |
|
|
ast::LitFloatUnsuffixed(ref n) => {
|
|
const_float(n.get().parse::<f64>().unwrap() as f64)
|
|
}
|
|
ast::LitBool(b) => const_bool(b)
|
|
}
|
|
}
|
|
|
|
fn compare_vals<T: PartialOrd>(a: T, b: T) -> Option<int> {
|
|
Some(if a == b { 0 } else if a < b { -1 } else { 1 })
|
|
}
|
|
pub fn compare_const_vals(a: &const_val, b: &const_val) -> Option<int> {
|
|
match (a, b) {
|
|
(&const_int(a), &const_int(b)) => compare_vals(a, b),
|
|
(&const_uint(a), &const_uint(b)) => compare_vals(a, b),
|
|
(&const_float(a), &const_float(b)) => compare_vals(a, b),
|
|
(&const_str(ref a), &const_str(ref b)) => compare_vals(a, b),
|
|
(&const_bool(a), &const_bool(b)) => compare_vals(a, b),
|
|
(&const_binary(ref a), &const_binary(ref b)) => compare_vals(a, b),
|
|
_ => None
|
|
}
|
|
}
|
|
|
|
pub fn compare_lit_exprs(tcx: &ty::ctxt, a: &Expr, b: &Expr) -> Option<int> {
|
|
compare_const_vals(&eval_const_expr(tcx, a), &eval_const_expr(tcx, b))
|
|
}
|