Threads: parsing of atomic instructions

Author: MaxDesiatov

Sources/WAT/BinaryInstructionEncoder.swift

@@ -392,4 +392,5 @@ extension BinaryInstructionEncoder {
         try encodeInstruction([0xFC, 0x10])
         try encodeImmediates(table: table)
     }
+    mutating func visitAtomicFence() throws { try encodeInstruction([0xFE, 0x03, 0x00]) }
 }

Sources/WAT/ParseTextInstruction.swift

@@ -332,6 +332,7 @@ func parseTextInstruction<V: InstructionVisitor>(keyword: String, expressionPars
     case "i64.trunc_sat_f32_u": return { return try $0.visitConversion(.i64TruncSatF32U) }
     case "i64.trunc_sat_f64_s": return { return try $0.visitConversion(.i64TruncSatF64S) }
     case "i64.trunc_sat_f64_u": return { return try $0.visitConversion(.i64TruncSatF64U) }
+    case "atomic.fence": return { return try $0.visitAtomicFence() }
     default: return nil
     }
 }

Sources/WasmParser/BinaryInstructionDecoder.swift

@@ -9,6 +9,7 @@ protocol BinaryInstructionDecoder {
     /// Claim the next byte to be decoded
     @inlinable func claimNextByte() throws -> UInt8
 
+    /// Throw an error due to unknown opcode.
     func throwUnknown(_ opcode: [UInt8]) throws -> Never
     /// Decode `block` immediates
     @inlinable mutating func visitBlock() throws -> BlockType
@@ -565,6 +566,22 @@ func parseBinaryInstruction(visitor: inout some InstructionVisitor, decoder: ino
         default:
             if try !visitor.visitUnknown([opcode0, opcode1]) { try decoder.throwUnknown([opcode0, opcode1]) }
         }
+    case 0xFE:
+
+        let opcode1 = try decoder.claimNextByte()
+        switch opcode1 {
+        case 0x03:
+
+            let opcode2 = try decoder.claimNextByte()
+            switch opcode2 {
+            case 0x00:
+                try visitor.visitAtomicFence()
+            default:
+                if try !visitor.visitUnknown([opcode0, opcode1, opcode2]) { try decoder.throwUnknown([opcode0, opcode1, opcode2]) }
+            }
+        default:
+            if try !visitor.visitUnknown([opcode0, opcode1]) { try decoder.throwUnknown([opcode0, opcode1]) }
+        }
     default:
         if try !visitor.visitUnknown([opcode0]) { try decoder.throwUnknown([opcode0]) }
     }

Sources/WasmParser/InstructionVisitor.swift

@@ -226,6 +226,7 @@ public enum Instruction: Equatable {
     case `tableSet`(table: UInt32)
     case `tableGrow`(table: UInt32)
     case `tableSize`(table: UInt32)
+    case `atomicFence`
 }
 
 /// A visitor that visits all instructions by a single visit method.
@@ -287,6 +288,7 @@ extension AnyInstructionVisitor {
     public mutating func visitTableSet(table: UInt32) throws { return try self.visit(.tableSet(table: table)) }
     public mutating func visitTableGrow(table: UInt32) throws { return try self.visit(.tableGrow(table: table)) }
     public mutating func visitTableSize(table: UInt32) throws { return try self.visit(.tableSize(table: table)) }
+    public mutating func visitAtomicFence() throws { return try self.visit(.atomicFence) }
 }
 
 /// A visitor for WebAssembly instructions.
@@ -398,6 +400,8 @@ public protocol InstructionVisitor {
     mutating func visitTableGrow(table: UInt32) throws
     /// Visiting `table.size` instruction.
     mutating func visitTableSize(table: UInt32) throws
+    /// Visiting `atomic.fence` instruction.
+    mutating func visitAtomicFence() throws
     /// Returns: `true` if the parser should silently proceed parsing.
     mutating func visitUnknown(_ opcode: [UInt8]) throws -> Bool
 }
@@ -458,6 +462,7 @@ extension InstructionVisitor {
         case let .tableSet(table): return try visitTableSet(table: table)
         case let .tableGrow(table): return try visitTableGrow(table: table)
         case let .tableSize(table): return try visitTableSize(table: table)
+        case .atomicFence: return try visitAtomicFence()
         }
     }
 }
@@ -516,6 +521,7 @@ extension InstructionVisitor {
     public mutating func visitTableSet(table: UInt32) throws {}
     public mutating func visitTableGrow(table: UInt32) throws {}
     public mutating func visitTableSize(table: UInt32) throws {}
+    public mutating func visitAtomicFence() throws {}
     public mutating func visitUnknown(_ opcode: [UInt8]) throws -> Bool { false }
 }
 

Sources/_CWasmKit/include/_CWasmKit.h

@@ -1,6 +1,7 @@
 #ifndef WASMKIT__CWASMKIT_H
 #define WASMKIT__CWASMKIT_H
 
+#include <stdatomic.h>
 #include <stddef.h>
 #include <stdint.h>
 #include <stdio.h>

Utilities/Instructions.json

@@ -201,5 +201,6 @@
   ["saturatingFloatToInt", "i64.trunc_sat_f32_s"      , ["0xFC", "0x04"], []                                                 , "conversion"],
   ["saturatingFloatToInt", "i64.trunc_sat_f32_u"      , ["0xFC", "0x05"], []                                                 , "conversion"],
   ["saturatingFloatToInt", "i64.trunc_sat_f64_s"      , ["0xFC", "0x06"], []                                                 , "conversion"],
-  ["saturatingFloatToInt", "i64.trunc_sat_f64_u"      , ["0xFC", "0x07"], []                                                 , "conversion"]
+  ["saturatingFloatToInt", "i64.trunc_sat_f64_u"      , ["0xFC", "0x07"], []                                                 , "conversion"],
+  ["threads"             , "atomic.fence"             , ["0xFE", "0x03", "0x00"], []                                         , null        ]
 ]