Use vector_map instead of btree_map in irep to save memory (rust-lang#620)

* Use vector_map instead of btree_map in irep to save memory

* Implement Serde serializer for the vec map

* remove to_json file

Author: danielsn

Cargo.lock

@@ -506,6 +506,7 @@ dependencies = [
  "smallvec",
  "snap",
  "tracing",
+ "vector-map",
 ]
 
 [[package]]
@@ -774,6 +775,17 @@ dependencies = [
  "winapi",
 ]
 
+[[package]]
+name = "contracts"
+version = "0.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c9424f2ca1e42776615720e5746eed6efa19866fdbaac2923ab51c294ac4d1f2"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn",
+]
+
 [[package]]
 name = "core"
 version = "0.0.0"
@@ -5831,6 +5843,16 @@ version = "0.8.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "f1bddf1187be692e79c5ffeab891132dfb0f236ed36a43c7ed39f1165ee20191"
 
+[[package]]
+name = "vector-map"
+version = "1.0.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "550f72ae94a45c0e2139188709e6c4179f0b5ff9bdaa435239ad19048b0cd68c"
+dependencies = [
+ "contracts",
+ "rand 0.7.3",
+]
+
 [[package]]
 name = "vergen"
 version = "5.1.0"

compiler/cbmc/Cargo.toml

@@ -19,6 +19,7 @@ num = "0.4.0"
 serde = {version = "1", features = ["derive"]}
 snap = "1"
 tracing = "0.1"
+vector-map = "1.0.1"
 rustc_middle = { path = "../rustc_middle" }
 rustc-demangle = "0.1.21"
 rustc_arena = { path = "../rustc_arena" }

compiler/cbmc/src/irep/irep.rs

@@ -6,17 +6,17 @@ use super::super::goto_program::{Location, Type};
 use super::super::MachineModel;
 use super::{IrepId, ToIrep};
 use num::BigInt;
-use std::collections::BTreeMap;
 use std::fmt::Debug;
+use vector_map::VecMap;
 
 /// The CBMC serialization format for goto-programs.
 /// CBMC implementation code is at:
 /// https://github.com/diffblue/cbmc/blob/develop/src/util/irep.h
-#[derive(Clone, Debug, PartialEq, Eq)]
+#[derive(Clone, Debug, PartialEq)]
 pub struct Irep {
     pub id: IrepId,
     pub sub: Vec<Irep>,
-    pub named_sub: BTreeMap<IrepId, Irep>,
+    pub named_sub: VecMap<IrepId, Irep>,
 }
 
 /// Getters
@@ -108,7 +108,7 @@ impl Irep {
     }
 
     pub fn just_id(id: IrepId) -> Irep {
-        Irep { id: id, sub: Vec::new(), named_sub: BTreeMap::new() }
+        Irep { id: id, sub: Vec::new(), named_sub: VecMap::new() }
     }
 
     pub fn just_int_id<T>(i: T) -> Irep
@@ -117,7 +117,7 @@ impl Irep {
     {
         Irep::just_id(IrepId::from_int(i))
     }
-    pub fn just_named_sub(named_sub: BTreeMap<IrepId, Irep>) -> Irep {
+    pub fn just_named_sub(named_sub: VecMap<IrepId, Irep>) -> Irep {
         Irep { id: IrepId::EmptyString, sub: vec![], named_sub: named_sub }
     }
 
@@ -126,7 +126,7 @@ impl Irep {
     }
 
     pub fn just_sub(sub: Vec<Irep>) -> Irep {
-        Irep { id: IrepId::EmptyString, sub: sub, named_sub: BTreeMap::new() }
+        Irep { id: IrepId::EmptyString, sub: sub, named_sub: VecMap::new() }
     }
 
     pub fn nil() -> Irep {

compiler/cbmc/src/irep/mod.rs

@@ -20,7 +20,6 @@ pub mod serialize;
 mod symbol;
 mod symbol_table;
 mod to_irep;
-mod to_json;
 
 pub use irep::Irep;
 pub use irep_id::IrepId;

compiler/cbmc/src/irep/serialize.rs

@@ -4,6 +4,23 @@
 use crate::irep::{Irep, IrepId, Symbol, SymbolTable};
 use serde::ser::{SerializeMap, Serializer};
 use serde::Serialize;
+use vector_map::VecMap;
+
+// Wrapper type to allow impl of trait (otherwise impossible when both trait and type are external).
+struct MapWrapper<'a, K, V>(&'a VecMap<K, V>);
+
+impl<K: serde::Serialize, V: serde::Serialize> Serialize for MapWrapper<'_, K, V> {
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        let mut obj = serializer.serialize_map(None)?;
+        for (k, v) in self.0 {
+            obj.serialize_entry(k, v)?;
+        }
+        obj.end()
+    }
+}
 
 impl Serialize for Irep {
     fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
@@ -16,7 +33,7 @@ impl Serialize for Irep {
             obj.serialize_entry("sub", &self.sub)?;
         }
         if !self.named_sub.is_empty() {
-            obj.serialize_entry("namedSub", &self.named_sub)?;
+            obj.serialize_entry("namedSub", &MapWrapper(&self.named_sub))?;
         }
         obj.end()
     }

compiler/cbmc/src/irep/symbol.rs

@@ -5,7 +5,7 @@ use super::Irep;
 /// A direct implementation of the CBMC serilization format for symbols implemented in
 /// https://github.com/diffblue/cbmc/blob/develop/src/util/symbol.h
 // TODO: do we want these members to be public?
-#[derive(Clone, Debug, PartialEq, Eq)]
+#[derive(Clone, Debug, PartialEq)]
 pub struct Symbol {
     pub typ: Irep,
     pub value: Irep,

compiler/cbmc/src/irep/symbol_table.rs

@@ -5,7 +5,7 @@ use std::collections::BTreeMap;
 
 /// A direct implementation of the CBMC serilization format for symbol tables implemented in
 /// https://github.com/diffblue/cbmc/blob/develop/src/util/symbol_table.h
-#[derive(Debug, PartialEq, Eq)]
+#[derive(Debug, PartialEq)]
 pub struct SymbolTable {
     pub symbol_table: BTreeMap<String, Symbol>,
 }