Adaptively determine the number of constant slots

Author: kateinoigakukun

Sources/WasmKit/Execution/Function.swift

@@ -189,6 +189,7 @@ struct WasmFunctionEntity {
             type: runtime.value.resolveType(type),
             locals: code.locals,
             functionIndex: index,
+            codeSize: code.expression.count,
             intercepting: runtime.value.interceptor != nil
         )
         let iseq = try code.withValue { code in

Sources/WasmKit/Execution/Instances.swift

@@ -133,11 +133,18 @@ public struct Instance {
                 target.write(" '\(name)'")
             }
             target.write(" ====\n")
+            guard case .uncompiled(let code) = function.wasm.code else {
+                fatalError("Already compiled!?")
+            }
             try function.ensureCompiled(runtime: RuntimeRef(runtime))
             let (iseq, locals, _) = function.assumeCompiled()
 
             // Print slot space information
-            let stackLayout = StackLayout(type: runtime.funcTypeInterner.resolve(function.type), numberOfLocals: locals)
+            let stackLayout = StackLayout(
+                type: runtime.funcTypeInterner.resolve(function.type),
+                numberOfLocals: locals,
+                codeSize: code.expression.count
+            )
             stackLayout.dump(to: &target, iseq: iseq)
 
             var context = InstructionPrintingContext(

Sources/WasmKit/Translator.swift

@@ -214,16 +214,18 @@ struct FrameHeaderLayout {
 
 struct StackLayout {
     let frameHeader: FrameHeaderLayout
-    let constantSlotSize: Int = 8
+    let constantSlotSize: Int
     let numberOfLocals: Int
 
     var stackRegBase: VReg {
         return VReg(numberOfLocals + constantSlotSize)
     }
 
-    init(type: FunctionType, numberOfLocals: Int) {
+    init(type: FunctionType, numberOfLocals: Int, codeSize: Int) {
         self.frameHeader = FrameHeaderLayout(type: type)
         self.numberOfLocals = numberOfLocals
+        // The number of constant slots is determined by the code size
+        self.constantSlotSize = max(codeSize / 20, 4)
     }
 
     func localReg(_ index: LocalIndex) -> VReg {
@@ -780,6 +782,7 @@ struct InstructionTranslator<Context: TranslatorContext>: InstructionVisitor {
         type: FunctionType,
         locals: [WasmTypes.ValueType],
         functionIndex: FunctionIndex,
+        codeSize: Int,
         intercepting: Bool
     ) {
         self.allocator = allocator
@@ -788,7 +791,11 @@ struct InstructionTranslator<Context: TranslatorContext>: InstructionVisitor {
         self.module = module
         self.iseqBuilder = ISeqBuilder(runtimeConfiguration: runtimeConfiguration)
         self.controlStack = ControlStack()
-        self.stackLayout = StackLayout(type: type, numberOfLocals: locals.count)
+        self.stackLayout = StackLayout(
+            type: type,
+            numberOfLocals: locals.count,
+            codeSize: codeSize
+        )
         self.valueStack = ValueStack(stackLayout: stackLayout)
         self.locals = Locals(types: type.parameters + locals)
         self.functionIndex = functionIndex