Add extended-const Wasm proposal support (#707)

* add extended-const Wasm proposal to config

* add Wasm spec tests for extended-const

* enable extended-const for tests

* apply rustfmt

* add ConstExpr to support extended const

* fix no_std build

* rename func_ref

* add module docs

Author: Robbepop

crates/wasmi/Cargo.toml

@@ -21,6 +21,7 @@ spin = { version = "0.9", default-features = false, features = [
     "spin_mutex",
     "rwlock",
 ] }
+smallvec = { version = "1.10.0", features = ["union"] }
 
 [dev-dependencies]
 wat = "1"

crates/wasmi/src/engine/config.rs

@@ -29,6 +29,8 @@ pub struct Config {
     reference_types: bool,
     /// Is `true` if the [`tail-call`] Wasm proposal is enabled.
     tail_call: bool,
+    /// Is `true` if the [`extended-const`] Wasm proposal is enabled.
+    extended_const: bool,
     /// Is `true` if Wasm instructions on `f32` and `f64` types are allowed.
     floats: bool,
     /// Is `true` if `wasmi` executions shall consume fuel.
@@ -201,6 +203,7 @@ impl Default for Config {
             bulk_memory: true,
             reference_types: true,
             tail_call: false,
+            extended_const: false,
             floats: true,
             consume_fuel: false,
             fuel_costs: FuelCosts::default(),
@@ -321,6 +324,18 @@ impl Config {
         self
     }
 
+    /// Enable or disable the [`extended-const`] Wasm proposal for the [`Config`].
+    ///
+    /// # Note
+    ///
+    /// Disabled by default.
+    ///
+    /// [`tail-call`]: https://github.com/WebAssembly/extended-const
+    pub fn wasm_extended_const(&mut self, enable: bool) -> &mut Self {
+        self.extended_const = enable;
+        self
+    }
+
     /// Enable or disable Wasm floating point (`f32` and `f64`) instructions and types.
     ///
     /// Enabled by default.
@@ -395,6 +410,7 @@ impl Config {
             bulk_memory: self.bulk_memory,
             reference_types: self.reference_types,
             tail_call: self.tail_call,
+            extended_const: self.extended_const,
             floats: self.floats,
             component_model: false,
             simd: false,
@@ -403,7 +419,6 @@ impl Config {
             multi_memory: false,
             exceptions: false,
             memory64: false,
-            extended_const: false,
             memory_control: false,
         }
     }

crates/wasmi/src/engine/func_builder/translator.rs

@@ -34,10 +34,10 @@ use crate::{
     },
     module::{
         BlockType,
+        ConstExpr,
         FuncIdx,
         FuncTypeIdx,
         GlobalIdx,
-        InitExpr,
         MemoryIdx,
         ModuleResources,
         DEFAULT_MEMORY_INDEX,
@@ -416,14 +416,14 @@ impl<'parser> FuncTranslator<'parser> {
     /// have a chance to be optimized to more efficient instructions.
     fn optimize_global_get(
         global_type: &GlobalType,
-        init_value: Option<&InitExpr>,
+        init_value: Option<&ConstExpr>,
     ) -> Option<Instruction> {
         if let (Mutability::Const, Some(init_expr)) = (global_type.mutability(), init_value) {
-            if let Some(value) = init_expr.to_const() {
+            if let Some(value) = init_expr.eval_const() {
                 // We can optimize `global.get` to the constant value.
                 return Some(Instruction::constant(value));
             }
-            if let Some(func_index) = init_expr.func_ref() {
+            if let Some(func_index) = init_expr.funcref() {
                 // We can optimize `global.get` to the equivalent `ref.func x` instruction.
                 let func_index = bytecode::FuncIdx::from(func_index.into_u32());
                 return Some(Instruction::RefFunc { func_index });

crates/wasmi/src/module/builder.rs

@@ -1,6 +1,7 @@
 use super::{
     export::ExternIdx,
     import::FuncTypeIdx,
+    ConstExpr,
     DataSegment,
     ElementSegment,
     ExternTypeIdx,
@@ -9,7 +10,6 @@ use super::{
     GlobalIdx,
     Import,
     ImportName,
-    InitExpr,
     Module,
 };
 use crate::{
@@ -33,7 +33,7 @@ pub struct ModuleBuilder<'engine> {
     pub tables: Vec<TableType>,
     pub memories: Vec<MemoryType>,
     pub globals: Vec<GlobalType>,
-    pub globals_init: Vec<InitExpr>,
+    pub globals_init: Vec<ConstExpr>,
     pub exports: BTreeMap<Box<str>, ExternIdx>,
     pub start: Option<FuncIdx>,
     pub func_bodies: Vec<FuncBody>,
@@ -90,7 +90,7 @@ impl<'a> ModuleResources<'a> {
     }
 
     /// Returns the global variable type and optional initial value.
-    pub fn get_global(&self, global_idx: GlobalIdx) -> (GlobalType, Option<&InitExpr>) {
+    pub fn get_global(&self, global_idx: GlobalIdx) -> (GlobalType, Option<&ConstExpr>) {
         let index = global_idx.into_u32() as usize;
         let len_imports = self.res.imports.len_globals();
         let global_type = self.get_type_of_global(global_idx);

crates/wasmi/src/module/data.rs

@@ -1,4 +1,4 @@
-use super::{InitExpr, MemoryIdx};
+use super::{ConstExpr, MemoryIdx};
 use alloc::sync::Arc;
 
 /// A Wasm [`Module`] data segment.
@@ -27,7 +27,7 @@ pub struct ActiveDataSegment {
     /// The linear memory that is to be initialized with this active segment.
     memory_index: MemoryIdx,
     /// The offset at which the data segment is initialized.
-    offset: InitExpr,
+    offset: ConstExpr,
 }
 
 impl ActiveDataSegment {
@@ -37,7 +37,7 @@ impl ActiveDataSegment {
     }
 
     /// Returns the offset expression of the [`ActiveDataSegment`].
-    pub fn offset(&self) -> &InitExpr {
+    pub fn offset(&self) -> &ConstExpr {
         &self.offset
     }
 }
@@ -50,7 +50,7 @@ impl From<wasmparser::DataKind<'_>> for DataSegmentKind {
                 offset_expr,
             } => {
                 let memory_index = MemoryIdx::from(memory_index);
-                let offset = InitExpr::new(offset_expr);
+                let offset = ConstExpr::new(offset_expr);
                 Self::Active(ActiveDataSegment {
                     memory_index,
                     offset,

crates/wasmi/src/module/element.rs

@@ -1,4 +1,4 @@
-use super::{InitExpr, TableIdx};
+use super::{ConstExpr, TableIdx};
 use crate::module::utils::WasmiValueType;
 use alloc::sync::Arc;
 use wasmi_core::ValueType;
@@ -19,7 +19,7 @@ pub struct ElementSegment {
 /// The items of an [`ElementSegment`].
 #[derive(Debug, Clone)]
 pub struct ElementSegmentItems {
-    exprs: Arc<[InitExpr]>,
+    exprs: Arc<[ConstExpr]>,
 }
 
 impl ElementSegmentItems {
@@ -36,22 +36,22 @@ impl ElementSegmentItems {
                 .map(|item| {
                     item.unwrap_or_else(|error| panic!("failed to parse element item: {error}"))
                 })
-                .map(InitExpr::new_funcref)
+                .map(ConstExpr::new_funcref)
                 .collect::<Arc<[_]>>(),
             wasmparser::ElementItems::Expressions(items) => items
                 .clone()
                 .into_iter()
                 .map(|item| {
                     item.unwrap_or_else(|error| panic!("failed to parse element item: {error}"))
                 })
-                .map(InitExpr::new)
+                .map(ConstExpr::new)
                 .collect::<Arc<[_]>>(),
         };
         Self { exprs }
     }
 
     /// Returns a shared reference to the items of the [`ElementSegmentItems`].
-    pub fn items(&self) -> &[InitExpr] {
+    pub fn items(&self) -> &[ConstExpr] {
         &self.exprs
     }
 }
@@ -73,7 +73,7 @@ pub struct ActiveElementSegment {
     /// The index of the Wasm table that is to be initialized.
     table_index: TableIdx,
     /// The offset where the Wasm table is to be initialized.
-    offset: InitExpr,
+    offset: ConstExpr,
 }
 
 impl ActiveElementSegment {
@@ -83,7 +83,7 @@ impl ActiveElementSegment {
     }
 
     /// Returns the offset expression of the [`ActiveElementSegment`].
-    pub fn offset(&self) -> &InitExpr {
+    pub fn offset(&self) -> &ConstExpr {
         &self.offset
     }
 }
@@ -96,7 +96,7 @@ impl From<wasmparser::ElementKind<'_>> for ElementSegmentKind {
                 offset_expr,
             } => {
                 let table_index = TableIdx::from(table_index);
-                let offset = InitExpr::new(offset_expr);
+                let offset = ConstExpr::new(offset_expr);
                 Self::Active(ActiveElementSegment {
                     table_index,
                     offset,

crates/wasmi/src/module/global.rs

@@ -1,4 +1,4 @@
-use super::InitExpr;
+use super::ConstExpr;
 use crate::GlobalType;
 
 /// The index of a global variable within a [`Module`].
@@ -33,13 +33,13 @@ pub struct Global {
     ///
     /// This is represented by a so called initializer expression
     /// that is run at module instantiation time.
-    init_expr: InitExpr,
+    init_expr: ConstExpr,
 }
 
 impl From<wasmparser::Global<'_>> for Global {
     fn from(global: wasmparser::Global<'_>) -> Self {
         let global_type = GlobalType::from_wasmparser(global.ty);
-        let init_expr = InitExpr::new(global.init_expr);
+        let init_expr = ConstExpr::new(global.init_expr);
         Self {
             global_type,
             init_expr,
@@ -49,7 +49,7 @@ impl From<wasmparser::Global<'_>> for Global {
 
 impl Global {
     /// Splits the [`Global`] into its global type and its global initializer.
-    pub fn into_type_and_init(self) -> (GlobalType, InitExpr) {
+    pub fn into_type_and_init(self) -> (GlobalType, ConstExpr) {
         (self.global_type, self.init_expr)
     }
 }