Introduce HashStable trait and base ICH implementations on it.

This initial commit provides implementations for HIR, MIR, and
everything that also needs to be supported for those two.

src/librustc/hir/map/definitions.rs

@@ -394,6 +394,10 @@ impl Definitions {
         }
     }
 
+    pub fn node_to_hir_id(&self, node_id: ast::NodeId) -> hir::HirId {
+        self.node_to_hir_id[node_id]
+    }
+
     /// Add a definition with a parent definition.
     pub fn create_def_with_parent(&mut self,
                                   parent: Option<DefIndex>,

src/librustc/ich/hcx.rs

@@ -0,0 +1,300 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use hir;
+use hir::def_id::DefId;
+use ich::{self, CachingCodemapView, DefPathHashes};
+use session::config::DebugInfoLevel::NoDebugInfo;
+use ty;
+
+use std::hash as std_hash;
+
+use syntax::ast;
+use syntax::attr;
+use syntax::ext::hygiene::SyntaxContext;
+use syntax::symbol::Symbol;
+use syntax_pos::Span;
+
+use rustc_data_structures::stable_hasher::{HashStable, StableHasher,
+                                           StableHasherResult};
+use rustc_data_structures::accumulate_vec::AccumulateVec;
+
+/// This is the context state available during incr. comp. hashing. It contains
+/// enough information to transform DefIds and HirIds into stable DefPaths (i.e.
+/// a reference to the TyCtxt) and it holds a few caches for speeding up various
+/// things (e.g. each DefId/DefPath is only hashed once).
+pub struct StableHashingContext<'a, 'tcx: 'a> {
+    tcx: ty::TyCtxt<'a, 'tcx, 'tcx>,
+    def_path_hashes: DefPathHashes<'a, 'tcx>,
+    codemap: CachingCodemapView<'tcx>,
+    hash_spans: bool,
+    hash_bodies: bool,
+    overflow_checks_enabled: bool,
+    node_id_hashing_mode: NodeIdHashingMode,
+    // A sorted array of symbol keys for fast lookup.
+    ignored_attr_names: Vec<Symbol>,
+}
+
+#[derive(PartialEq, Eq, Clone, Copy)]
+pub enum NodeIdHashingMode {
+    Ignore,
+    HashDefPath,
+    HashTraitsInScope,
+}
+
+impl<'a, 'tcx: 'a> StableHashingContext<'a, 'tcx> {
+
+    pub fn new(tcx: ty::TyCtxt<'a, 'tcx, 'tcx>) -> Self {
+        let hash_spans_initial = tcx.sess.opts.debuginfo != NoDebugInfo;
+        let check_overflow_initial = tcx.sess.overflow_checks();
+
+        let mut ignored_attr_names: Vec<_> = ich::IGNORED_ATTRIBUTES
+            .iter()
+            .map(|&s| Symbol::intern(s))
+            .collect();
+
+        ignored_attr_names.sort();
+
+        StableHashingContext {
+            tcx: tcx,
+            def_path_hashes: DefPathHashes::new(tcx),
+            codemap: CachingCodemapView::new(tcx),
+            hash_spans: hash_spans_initial,
+            hash_bodies: true,
+            overflow_checks_enabled: check_overflow_initial,
+            node_id_hashing_mode: NodeIdHashingMode::HashDefPath,
+            ignored_attr_names: ignored_attr_names,
+        }
+    }
+
+    #[inline]
+    pub fn while_hashing_hir_bodies<F: FnOnce(&mut Self)>(&mut self,
+                                                          hash_bodies: bool,
+                                                          f: F) {
+        let prev_hash_bodies = self.hash_bodies;
+        self.hash_bodies = hash_bodies;
+        f(self);
+        self.hash_bodies = prev_hash_bodies;
+    }
+
+    #[inline]
+    pub fn while_hashing_spans<F: FnOnce(&mut Self)>(&mut self,
+                                                     hash_spans: bool,
+                                                     f: F) {
+        let prev_hash_spans = self.hash_spans;
+        self.hash_spans = hash_spans;
+        f(self);
+        self.hash_spans = prev_hash_spans;
+    }
+
+    #[inline]
+    pub fn with_node_id_hashing_mode<F: FnOnce(&mut Self)>(&mut self,
+                                                           mode: NodeIdHashingMode,
+                                                           f: F) {
+        let prev = self.node_id_hashing_mode;
+        self.node_id_hashing_mode = mode;
+        f(self);
+        self.node_id_hashing_mode = prev;
+    }
+
+    #[inline]
+    pub fn tcx(&self) -> ty::TyCtxt<'a, 'tcx, 'tcx> {
+        self.tcx
+    }
+
+    #[inline]
+    pub fn def_path_hash(&mut self, def_id: DefId) -> u64 {
+        self.def_path_hashes.hash(def_id)
+    }
+
+    #[inline]
+    pub fn hash_spans(&self) -> bool {
+        self.hash_spans
+    }
+
+    #[inline]
+    pub fn hash_bodies(&self) -> bool {
+        self.hash_bodies
+    }
+
+    #[inline]
+    pub fn codemap(&mut self) -> &mut CachingCodemapView<'tcx> {
+        &mut self.codemap
+    }
+
+    #[inline]
+    pub fn is_ignored_attr(&self, name: Symbol) -> bool {
+        self.ignored_attr_names.binary_search(&name).is_ok()
+    }
+
+    pub fn hash_hir_item_like<F: FnOnce(&mut Self)>(&mut self,
+                                                    item_attrs: &[ast::Attribute],
+                                                    f: F) {
+        let prev_overflow_checks = self.overflow_checks_enabled;
+        if attr::contains_name(item_attrs, "rustc_inherit_overflow_checks") {
+            self.overflow_checks_enabled = true;
+        }
+        let prev_hash_node_ids = self.node_id_hashing_mode;
+        self.node_id_hashing_mode = NodeIdHashingMode::Ignore;
+
+        f(self);
+
+        self.node_id_hashing_mode = prev_hash_node_ids;
+        self.overflow_checks_enabled = prev_overflow_checks;
+    }
+
+    #[inline]
+    pub fn binop_can_panic_at_runtime(&self, binop: hir::BinOp_) -> bool
+    {
+        match binop {
+            hir::BiAdd |
+            hir::BiSub |
+            hir::BiMul => self.overflow_checks_enabled,
+
+            hir::BiDiv |
+            hir::BiRem => true,
+
+            hir::BiAnd |
+            hir::BiOr |
+            hir::BiBitXor |
+            hir::BiBitAnd |
+            hir::BiBitOr |
+            hir::BiShl |
+            hir::BiShr |
+            hir::BiEq |
+            hir::BiLt |
+            hir::BiLe |
+            hir::BiNe |
+            hir::BiGe |
+            hir::BiGt => false
+        }
+    }
+
+    #[inline]
+    pub fn unop_can_panic_at_runtime(&self, unop: hir::UnOp) -> bool
+    {
+        match unop {
+            hir::UnDeref |
+            hir::UnNot => false,
+            hir::UnNeg => self.overflow_checks_enabled,
+        }
+    }
+}
+
+
+impl<'a, 'tcx> HashStable<StableHashingContext<'a, 'tcx>> for ast::NodeId {
+    fn hash_stable<W: StableHasherResult>(&self,
+                                          hcx: &mut StableHashingContext<'a, 'tcx>,
+                                          hasher: &mut StableHasher<W>) {
+        match hcx.node_id_hashing_mode {
+            NodeIdHashingMode::Ignore => {
+                // Most NodeIds in the HIR can be ignored, but if there is a
+                // corresponding entry in the `trait_map` we need to hash that.
+                // Make sure we don't ignore too much by checking that there is
+                // no entry in a debug_assert!().
+                debug_assert!(hcx.tcx.trait_map.get(self).is_none());
+            }
+            NodeIdHashingMode::HashDefPath => {
+                hcx.tcx.hir.definitions().node_to_hir_id(*self).hash_stable(hcx, hasher);
+            }
+            NodeIdHashingMode::HashTraitsInScope => {
+                if let Some(traits) = hcx.tcx.trait_map.get(self) {
+                    // The ordering of the candidates is not fixed. So we hash
+                    // the def-ids and then sort them and hash the collection.
+                    let mut candidates: AccumulateVec<[_; 8]> =
+                        traits.iter()
+                              .map(|&hir::TraitCandidate { def_id, import_id: _ }| {
+                                  hcx.def_path_hash(def_id)
+                              })
+                              .collect();
+                    if traits.len() > 1 {
+                        candidates.sort();
+                    }
+                    candidates.hash_stable(hcx, hasher);
+                }
+            }
+        }
+    }
+}
+
+impl<'a, 'tcx> HashStable<StableHashingContext<'a, 'tcx>> for Span {
+
+    // Hash a span in a stable way. We can't directly hash the span's BytePos
+    // fields (that would be similar to hashing pointers, since those are just
+    // offsets into the CodeMap). Instead, we hash the (file name, line, column)
+    // triple, which stays the same even if the containing FileMap has moved
+    // within the CodeMap.
+    // Also note that we are hashing byte offsets for the column, not unicode
+    // codepoint offsets. For the purpose of the hash that's sufficient.
+    // Also, hashing filenames is expensive so we avoid doing it twice when the
+    // span starts and ends in the same file, which is almost always the case.
+    fn hash_stable<W: StableHasherResult>(&self,
+                                          hcx: &mut StableHashingContext<'a, 'tcx>,
+                                          hasher: &mut StableHasher<W>) {
+        use syntax_pos::Pos;
+
+        if !hcx.hash_spans {
+            return
+        }
+
+        // If this is not an empty or invalid span, we want to hash the last
+        // position that belongs to it, as opposed to hashing the first
+        // position past it.
+        let span_hi = if self.hi > self.lo {
+            // We might end up in the middle of a multibyte character here,
+            // but that's OK, since we are not trying to decode anything at
+            // this position.
+            self.hi - ::syntax_pos::BytePos(1)
+        } else {
+            self.hi
+        };
+
+        {
+            let loc1 = hcx.codemap().byte_pos_to_line_and_col(self.lo);
+            let loc1 = loc1.as_ref()
+                           .map(|&(ref fm, line, col)| (&fm.name[..], line, col.to_usize()))
+                           .unwrap_or(("???", 0, 0));
+
+            let loc2 = hcx.codemap().byte_pos_to_line_and_col(span_hi);
+            let loc2 = loc2.as_ref()
+                           .map(|&(ref fm, line, col)| (&fm.name[..], line, col.to_usize()))
+                           .unwrap_or(("???", 0, 0));
+
+            if loc1.0 == loc2.0 {
+                std_hash::Hash::hash(&0u8, hasher);
+
+                std_hash::Hash::hash(loc1.0, hasher);
+                std_hash::Hash::hash(&loc1.1, hasher);
+                std_hash::Hash::hash(&loc1.2, hasher);
+
+                // Do not hash the file name twice
+                std_hash::Hash::hash(&loc2.1, hasher);
+                std_hash::Hash::hash(&loc2.2, hasher);
+            } else {
+                std_hash::Hash::hash(&1u8, hasher);
+
+                std_hash::Hash::hash(loc1.0, hasher);
+                std_hash::Hash::hash(&loc1.1, hasher);
+                std_hash::Hash::hash(&loc1.2, hasher);
+
+                std_hash::Hash::hash(loc2.0, hasher);
+                std_hash::Hash::hash(&loc2.1, hasher);
+                std_hash::Hash::hash(&loc2.2, hasher);
+            }
+        }
+
+        if self.ctxt == SyntaxContext::empty() {
+            0u8.hash_stable(hcx, hasher);
+        } else {
+            1u8.hash_stable(hcx, hasher);
+            self.source_callsite().hash_stable(hcx, hasher);
+        }
+    }
+}

src/librustc/ich/impls_const_math.rs

@@ -0,0 +1,71 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! This module contains `HashStable` implementations for various data types
+//! from `rustc_const_math` in no particular order.
+
+impl_stable_hash_for!(enum ::rustc_const_math::ConstFloat {
+    F32(val),
+    F64(val)
+});
+
+impl_stable_hash_for!(enum ::rustc_const_math::ConstInt {
+    I8(val),
+    I16(val),
+    I32(val),
+    I64(val),
+    I128(val),
+    Isize(val),
+    U8(val),
+    U16(val),
+    U32(val),
+    U64(val),
+    U128(val),
+    Usize(val)
+});
+
+impl_stable_hash_for!(enum ::rustc_const_math::ConstIsize {
+    Is16(i16),
+    Is32(i32),
+    Is64(i64)
+});
+
+impl_stable_hash_for!(enum ::rustc_const_math::ConstUsize {
+    Us16(i16),
+    Us32(i32),
+    Us64(i64)
+});
+
+impl_stable_hash_for!(enum ::rustc_const_math::ConstMathErr {
+    NotInRange,
+    CmpBetweenUnequalTypes,
+    UnequalTypes(op),
+    Overflow(op),
+    ShiftNegative,
+    DivisionByZero,
+    RemainderByZero,
+    UnsignedNegation,
+    ULitOutOfRange(int_ty),
+    LitOutOfRange(int_ty)
+});
+
+impl_stable_hash_for!(enum ::rustc_const_math::Op {
+    Add,
+    Sub,
+    Mul,
+    Div,
+    Rem,
+    Shr,
+    Shl,
+    Neg,
+    BitAnd,
+    BitOr,
+    BitXor
+});