(opt): Small String Optimisations (SSO)

som-interpreter-bc/Cargo.toml

@@ -29,3 +29,6 @@ num-traits = "0.2.11"
 
 # random numbers
 rand = "0.7.3"
+
+# small string optimisation
+smartstring = "0.2.3"

som-interpreter-bc/src/compiler.rs

@@ -7,6 +7,7 @@ use std::rc::{Rc, Weak};
 
 use indexmap::{IndexMap, IndexSet};
 use num_bigint::BigInt;
+use smartstring::alias::String as SmallString;
 
 use som_core::ast;
 use som_core::bytecode::Bytecode;
@@ -21,7 +22,7 @@ use crate::SOMRef;
 #[derive(Debug, Clone)]
 pub enum Literal {
     Symbol(Interned),
-    String(Rc<String>),
+    String(SmallString),
     Double(f64),
     Integer(i64),
     BigInteger(BigInt),
@@ -290,7 +291,7 @@ impl MethodCodegen for ast::Expression {
                         ast::Literal::Symbol(val) => {
                             Literal::Symbol(ctxt.intern_symbol(val.as_str()))
                         }
-                        ast::Literal::String(val) => Literal::String(Rc::new(val.clone())),
+                        ast::Literal::String(val) => Literal::String(val.into()),
                         ast::Literal::Double(val) => Literal::Double(*val),
                         ast::Literal::Integer(val) => Literal::Integer(*val),
                         ast::Literal::BigInteger(val) => Literal::BigInteger(val.parse().unwrap()),

som-interpreter-bc/src/main.rs

@@ -4,7 +4,6 @@
 #![warn(missing_docs)]
 
 use std::path::PathBuf;
-use std::rc::Rc;
 
 use anyhow::anyhow;
 use structopt::StructOpt;
@@ -76,7 +75,7 @@ fn main() -> anyhow::Result<()> {
 
             let args = std::iter::once(String::from(file_stem))
                 .chain(opts.args.iter().cloned())
-                .map(Rc::new)
+                .map(Into::into)
                 .map(Value::String)
                 .collect();
 

som-interpreter-bc/src/primitives/double.rs

@@ -1,5 +1,3 @@
-use std::rc::Rc;
-
 use crate::interpreter::Interpreter;
 use crate::primitives::PrimitiveFn;
 use crate::universe::Universe;
@@ -49,7 +47,7 @@ fn as_string(interpreter: &mut Interpreter, _: &mut Universe) {
     frame
         .borrow_mut()
         .stack
-        .push(Value::String(Rc::new(value.to_string())));
+        .push(Value::String(value.to_string().into()));
 }
 
 fn as_integer(interpreter: &mut Interpreter, _: &mut Universe) {

som-interpreter-bc/src/primitives/integer.rs

@@ -1,5 +1,3 @@
-use std::rc::Rc;
-
 use num_bigint::{BigInt, Sign};
 use num_traits::ToPrimitive;
 use rand::distributions::Uniform;
@@ -71,7 +69,10 @@ fn as_string(interpreter: &mut Interpreter, _: &mut Universe) {
     };
 
     {
-        frame.borrow_mut().stack.push(Value::String(Rc::new(value)));
+        frame
+            .borrow_mut()
+            .stack
+            .push(Value::String(value.to_string().into()));
         return;
     }
 }

som-interpreter-bc/src/primitives/string.rs

@@ -1,7 +1,6 @@
 use std::collections::hash_map::DefaultHasher;
 use std::convert::TryFrom;
 use std::hash::Hasher;
-use std::rc::Rc;
 
 use crate::interpreter::Interpreter;
 use crate::primitives::PrimitiveFn;
@@ -144,7 +143,7 @@ fn concatenate(interpreter: &mut Interpreter, universe: &mut Universe) {
     frame
         .borrow_mut()
         .stack
-        .push(Value::String(Rc::new(format!("{}{}", s1, s2))))
+        .push(Value::String(format!("{}{}", s1, s2).into()))
 }
 
 fn as_symbol(interpreter: &mut Interpreter, universe: &mut Universe) {
@@ -196,7 +195,7 @@ fn prim_substring_from_to(interpreter: &mut Interpreter, universe: &mut Universe
         (_, _, _) => panic!("'{}': wrong types", SIGNATURE),
     };
 
-    let string = Rc::new(value.chars().skip(from).take(to - from).collect());
+    let string = value.chars().skip(from).take(to - from).collect();
 
     frame.borrow_mut().stack.push(Value::String(string))
 }

som-interpreter-bc/src/primitives/symbol.rs

@@ -1,5 +1,3 @@
-use std::rc::Rc;
-
 use crate::interpreter::Interpreter;
 use crate::primitives::PrimitiveFn;
 use crate::universe::Universe;
@@ -15,9 +13,9 @@ fn as_string(interpreter: &mut Interpreter, universe: &mut Universe) {
         Value::Symbol(sym) => sym,
     ]);
 
-    frame.borrow_mut().stack.push(Value::String(Rc::new(
-        universe.lookup_symbol(sym).to_string(),
-    )));
+    frame.borrow_mut().stack.push(Value::String(
+        universe.lookup_symbol(sym).to_string().into(),
+    ));
 }
 
 /// Search for a primitive matching the given signature.

som-interpreter-bc/src/value.rs

@@ -2,6 +2,7 @@ use std::fmt;
 use std::rc::Rc;
 
 use num_bigint::BigInt;
+use smartstring::alias::String as SmallString;
 
 use crate::block::Block;
 use crate::class::Class;
@@ -29,7 +30,7 @@ pub enum Value {
     /// An interned symbol value.
     Symbol(Interned),
     /// A string value.
-    String(Rc<String>),
+    String(SmallString),
     /// An array of values.
     Array(SOMRef<Vec<Self>>),
     /// A block value, ready to be evaluated.