From 776cf133bc668f0372531aa49b4f75280341def0 Mon Sep 17 00:00:00 2001
From: Volker <Volker@Volker.fritz.box>
Date: Fri, 27 Jul 2018 17:51:36 +0200
Subject: [PATCH] Use UNREACHABLE operation after endless loop.

---
 .../jwebassembly/binary/BinaryModuleWriter.java |  3 +++
 .../jwebassembly/binary/InstructionOpcodes.java |  2 ++
 .../jwebassembly/module/ModuleGenerator.java    | 17 +----------------
 .../jwebassembly/module/WasmBlockOperator.java  |  1 +
 .../jwebassembly/text/TextModuleWriter.java     |  3 +++
 5 files changed, 10 insertions(+), 16 deletions(-)

diff --git a/src/de/inetsoftware/jwebassembly/binary/BinaryModuleWriter.java b/src/de/inetsoftware/jwebassembly/binary/BinaryModuleWriter.java
index 30901f9..4a1e5eb 100644
--- a/src/de/inetsoftware/jwebassembly/binary/BinaryModuleWriter.java
+++ b/src/de/inetsoftware/jwebassembly/binary/BinaryModuleWriter.java
@@ -727,6 +727,9 @@ public class BinaryModuleWriter extends ModuleWriter implements InstructionOpcod
                 codeStream.write( LOOP );
                 codeStream.write( 0x40 ); // void; the return type of the loop. currently we does not use it
                 break;
+            case UNREACHABLE:
+                codeStream.write( UNREACHABLE );
+                break;
             default:
                 throw new Error( "Unknown block: " + op );
         }
diff --git a/src/de/inetsoftware/jwebassembly/binary/InstructionOpcodes.java b/src/de/inetsoftware/jwebassembly/binary/InstructionOpcodes.java
index fa6b349..a97d0d7 100644
--- a/src/de/inetsoftware/jwebassembly/binary/InstructionOpcodes.java
+++ b/src/de/inetsoftware/jwebassembly/binary/InstructionOpcodes.java
@@ -25,6 +25,8 @@ package de.inetsoftware.jwebassembly.binary;
  */
 interface InstructionOpcodes {
 
+    static final int UNREACHABLE = 0x00;
+
     static final int NOP       = 0x01;
 
     // === Control flow operators ====
diff --git a/src/de/inetsoftware/jwebassembly/module/ModuleGenerator.java b/src/de/inetsoftware/jwebassembly/module/ModuleGenerator.java
index 9f161e9..a2567b2 100644
--- a/src/de/inetsoftware/jwebassembly/module/ModuleGenerator.java
+++ b/src/de/inetsoftware/jwebassembly/module/ModuleGenerator.java
@@ -910,22 +910,7 @@ public class ModuleGenerator {
                 // if a method ends with a loop without a break then code after the loop is no reachable
                 // Java does not need a return byte code in this case
                 // But WebAssembly need the dead code to validate
-                switch( returnType ) {
-                    case i32:
-                        instructions.add( new WasmConstInstruction( 0, byteCode.getCodePosition() ) );
-                        break;
-                    case i64:
-                        instructions.add( new WasmConstInstruction( 0L, byteCode.getCodePosition() ) );
-                        break;
-                    case f32:
-                        instructions.add( new WasmConstInstruction( 0F, byteCode.getCodePosition() ) );
-                        break;
-                    case f64:
-                        instructions.add( new WasmConstInstruction( 0D, byteCode.getCodePosition() ) );
-                        break;
-                    default:
-                }
-                instructions.add( new WasmBlockInstruction( WasmBlockOperator.RETURN, null, byteCode.getCodePosition() ) );
+                instructions.add( new WasmBlockInstruction( WasmBlockOperator.UNREACHABLE, null, byteCode.getCodePosition() ) );
             }
         } catch( WasmException ex ) {
             throw ex;
diff --git a/src/de/inetsoftware/jwebassembly/module/WasmBlockOperator.java b/src/de/inetsoftware/jwebassembly/module/WasmBlockOperator.java
index 8a6b14a..60fc2ba 100644
--- a/src/de/inetsoftware/jwebassembly/module/WasmBlockOperator.java
+++ b/src/de/inetsoftware/jwebassembly/module/WasmBlockOperator.java
@@ -33,4 +33,5 @@ public enum WasmBlockOperator {
     BR_IF,
     BR_TABLE,
     LOOP,
+    UNREACHABLE,
 }
diff --git a/src/de/inetsoftware/jwebassembly/text/TextModuleWriter.java b/src/de/inetsoftware/jwebassembly/text/TextModuleWriter.java
index 61ae1e0..a835fe8 100644
--- a/src/de/inetsoftware/jwebassembly/text/TextModuleWriter.java
+++ b/src/de/inetsoftware/jwebassembly/text/TextModuleWriter.java
@@ -311,6 +311,9 @@ public class TextModuleWriter extends ModuleWriter {
                 name = "loop";
                 insetAfter++;
                 break;
+            case UNREACHABLE:
+                name = "unreachable";
+                break;
             default:
                 throw new Error( "Unknown block: " + op );
         }