Remove ifThenElse instruction

swiftwasm · Apr 7, 2024 · 2a5d6f9 · 2a5d6f9
1 parent de39caa
commit 2a5d6f9
Show file tree

Hide file tree

Showing 5 changed files with 11 additions and 31 deletions.
diff --git a/Sources/WasmKit/Execution/Instructions/Control.swift b/Sources/WasmKit/Execution/Instructions/Control.swift
@@ -10,25 +10,15 @@ extension ExecutionState {
 
     typealias BlockType = Instruction.BlockType
 
-    mutating func ifThen(runtime: Runtime, stack: inout Stack, endRef: ExpressionRef, type: BlockType) {
+    mutating func ifThen(runtime: Runtime, stack: inout Stack, elseOrEndRef: ExpressionRef, type: BlockType) {
         let isTrue = stack.popValue().i32 != 0
         if isTrue {
             programCounter += 1
         } else {
-            programCounter += endRef.relativeOffset
+            programCounter += elseOrEndRef.relativeOffset
         }
     }
 
-    mutating func ifThenElse(runtime: Runtime, stack: inout Stack, elseRef: ExpressionRef, type: BlockType) {
-        let isTrue = stack.popValue().i32 != 0
-        let addendToPC: Int
-        if isTrue {
-            addendToPC = 1
-        } else {
-            addendToPC = elseRef.relativeOffset
-        }
-        programCounter += addendToPC
-    }
     mutating func end(runtime: Runtime, stack: inout Stack) {
         fatalError()
     }

diff --git a/Sources/WasmKit/Execution/Instructions/Instruction.swift b/Sources/WasmKit/Execution/Instructions/Instruction.swift
@@ -6,8 +6,7 @@ enum Instruction: Equatable {
     case globalSet(index: GlobalIndex)
     case unreachable
     case nop
-    case ifThen(endRef: ExpressionRef, type: BlockType)
-    case ifThenElse(elseRef: ExpressionRef, type: BlockType)
+    case ifThen(elseOrEndRef: ExpressionRef, type: BlockType)
     case end
     case `else`(endRef: ExpressionRef)
     case br(offset: Int32, copyCount: UInt32, popCount: UInt32)

diff --git a/Sources/WasmKit/Execution/Runtime/InstDispatch.swift b/Sources/WasmKit/Execution/Runtime/InstDispatch.swift
@@ -19,11 +19,8 @@ extension ExecutionState {
         case .nop:
             try self.nop(runtime: runtime, stack: &stack)
             return true
-        case .ifThen(let endRef, let type):
-            self.ifThen(runtime: runtime, stack: &stack, endRef: endRef, type: type)
-            return true
-        case .ifThenElse(let elseRef, let type):
-            self.ifThenElse(runtime: runtime, stack: &stack, elseRef: elseRef, type: type)
+        case .ifThen(let elseOrEndRef, let type):
+            self.ifThen(runtime: runtime, stack: &stack, elseOrEndRef: elseOrEndRef, type: type)
             return true
         case .end:
             self.end(runtime: runtime, stack: &stack)
@@ -254,7 +251,6 @@ extension Instruction {
         case .unreachable: return "unreachable"
         case .nop: return "nop"
         case .ifThen: return "ifThen"
-        case .ifThenElse: return "ifThenElse"
         case .end: return "end"
         case .`else`: return "`else`"
         case .br: return "br"

diff --git a/Sources/WasmKit/Translator.swift b/Sources/WasmKit/Translator.swift
@@ -417,15 +417,13 @@ struct InstructionTranslator: InstructionVisitor {
         )
         let selfPC = iseqBuilder.insertingPC
         iseqBuilder.emitWithLabel(endLabel) { iseqBuilder, endPC in
-            let endRef = ExpressionRef(from: selfPC, to: endPC)
+            let elseOrEndRef: ExpressionRef
             if let elsePC = iseqBuilder.resolveLabel(elseLabel) {
-                return .ifThenElse(
-                    elseRef: ExpressionRef(from: selfPC, to: elsePC),
-                    type: Instruction.BlockType(blockType)
-                )
+                elseOrEndRef = ExpressionRef(from: selfPC, to: elsePC)
             } else {
-                return .ifThen(endRef: endRef, type: Instruction.BlockType(blockType))
+                elseOrEndRef = ExpressionRef(from: selfPC, to: endPC)
             }
+            return .ifThen(elseOrEndRef: elseOrEndRef, type: Instruction.BlockType(blockType))
         }
     }
 

diff --git a/Utilities/generate_inst_dispatch.swift b/Utilities/generate_inst_dispatch.swift
@@ -131,11 +131,8 @@ let instructions: [Instruction] = [
     Instruction(name: "unreachable", isControl: true, mayThrow: true, immediates: []),
     Instruction(name: "nop", isControl: true, mayThrow: true, immediates: []),
     Instruction(name: "ifThen", isControl: true, immediates: [
-        Immediate(name: "endRef", type: "ExpressionRef"),
-        Immediate(name: "type", type: "BlockType")
-    ]),
-    Instruction(name: "ifThenElse", isControl: true, immediates: [
-        Immediate(name: "elseRef", type: "ExpressionRef"),
+        // elseRef for if-then-else-end sequence, endRef for if-then-end sequence
+        Immediate(name: "elseOrEndRef", type: "ExpressionRef"),
         Immediate(name: "type", type: "BlockType")
     ]),
     Instruction(name: "end", isControl: true, immediates: []),