From 11f338eea86cd84b1d58f5fe585251f2b041cb03 Mon Sep 17 00:00:00 2001
From: Volker Berlin <volker.berlin@googlemail.com>
Date: Sat, 25 Apr 2020 22:22:18 +0200
Subject: [PATCH] implements dup_x2 instruction

---
 .../module/JavaMethodWasmCodeBuilder.java     |  5 +--
 .../jwebassembly/module/WasmCodeBuilder.java  | 33 ++++++++++++++++++-
 .../jwebassembly/runtime/ArrayOperations.java | 14 ++++++++
 3 files changed, 49 insertions(+), 3 deletions(-)

diff --git a/src/de/inetsoftware/jwebassembly/module/JavaMethodWasmCodeBuilder.java b/src/de/inetsoftware/jwebassembly/module/JavaMethodWasmCodeBuilder.java
index e03c4cc..1caa27d 100644
--- a/src/de/inetsoftware/jwebassembly/module/JavaMethodWasmCodeBuilder.java
+++ b/src/de/inetsoftware/jwebassembly/module/JavaMethodWasmCodeBuilder.java
@@ -311,9 +311,10 @@ class JavaMethodWasmCodeBuilder extends WasmCodeBuilder {
                         break;
                     case 91: // dup_x2
                     case 94: // dup2_x2
+                        addDupX2Instruction( codePos, lineNumber );
+                        break;
                     case 95: // swap
-                        // can be do with functions with more as one return value in future WASM standard
-                        throw new WasmException( "Stack duplicate is not supported in current WASM. try to save immediate values in a local variable: "
+                        throw new WasmException( "Stack swap is not supported in current WASM. try to save immediate values in a local variable: "
                                         + op, lineNumber );
                     case 96: // iadd
                         addNumericInstruction( NumericOperator.add, ValueType.i32, codePos, lineNumber );
diff --git a/src/de/inetsoftware/jwebassembly/module/WasmCodeBuilder.java b/src/de/inetsoftware/jwebassembly/module/WasmCodeBuilder.java
index 3af6158..49e791e 100644
--- a/src/de/inetsoftware/jwebassembly/module/WasmCodeBuilder.java
+++ b/src/de/inetsoftware/jwebassembly/module/WasmCodeBuilder.java
@@ -348,7 +348,7 @@ public abstract class WasmCodeBuilder {
         AnyType type2 = findValueTypeFromStack( 2, javaCodePos );
 
         int varIndex1 = getTempVariable( type1, javaCodePos, javaCodePos + 1 );
-        int varIndex2 = getTempVariable( type2, javaCodePos, javaCodePos + 1 );;
+        int varIndex2 = getTempVariable( type2, javaCodePos, javaCodePos + 1 );
 
         // save in temp variables
         instructions.add( new WasmLocalInstruction( VariableOperator.set, varIndex1, localVariables, javaCodePos, lineNumber ) );
@@ -360,6 +360,37 @@ public abstract class WasmCodeBuilder {
         instructions.add( new WasmLocalInstruction( VariableOperator.get, varIndex1, localVariables, javaCodePos, lineNumber ) );
     }
 
+    /**
+     * Simulate the dup_x2 Java byte code instruction.<p>
+     * 
+     * ..., value3, value2, value1 → ..., value1, value3, value2, value1
+     * 
+     * @param javaCodePos
+     *            the code position/offset in the Java method
+     * @param lineNumber
+     *            the line number in the Java source code
+     */
+    protected void addDupX2Instruction( int javaCodePos, int lineNumber ) {
+        AnyType type1 = findValueTypeFromStack( 1, javaCodePos );
+        AnyType type2 = findValueTypeFromStack( 2, javaCodePos );
+        AnyType type3 = findValueTypeFromStack( 3, javaCodePos );
+
+        int varIndex1 = getTempVariable( type1, javaCodePos, javaCodePos + 1 );
+        int varIndex2 = getTempVariable( type2, javaCodePos, javaCodePos + 1 );
+        int varIndex3 = getTempVariable( type3, javaCodePos, javaCodePos + 1 );
+
+        // save in temp variables
+        instructions.add( new WasmLocalInstruction( VariableOperator.set, varIndex1, localVariables, javaCodePos, lineNumber ) );
+        instructions.add( new WasmLocalInstruction( VariableOperator.set, varIndex2, localVariables, javaCodePos, lineNumber ) );
+        instructions.add( new WasmLocalInstruction( VariableOperator.set, varIndex3, localVariables, javaCodePos, lineNumber ) );
+
+        // and restore it in new order on the stack
+        instructions.add( new WasmLocalInstruction( VariableOperator.get, varIndex1, localVariables, javaCodePos, lineNumber ) );
+        instructions.add( new WasmLocalInstruction( VariableOperator.get, varIndex3, localVariables, javaCodePos, lineNumber ) );
+        instructions.add( new WasmLocalInstruction( VariableOperator.get, varIndex2, localVariables, javaCodePos, lineNumber ) );
+        instructions.add( new WasmLocalInstruction( VariableOperator.get, varIndex1, localVariables, javaCodePos, lineNumber ) );
+    }
+
     /**
      * Add a global instruction
      * 
diff --git a/test/de/inetsoftware/jwebassembly/runtime/ArrayOperations.java b/test/de/inetsoftware/jwebassembly/runtime/ArrayOperations.java
index e0967e3..6af6ab1 100644
--- a/test/de/inetsoftware/jwebassembly/runtime/ArrayOperations.java
+++ b/test/de/inetsoftware/jwebassembly/runtime/ArrayOperations.java
@@ -59,6 +59,7 @@ public class ArrayOperations extends AbstractBaseTest {
             addParam( list, script, "loopObject" );
             addParam( list, script, "copyBack2Front" );
             addParam( list, script, "copyFront2Back" );
+            addParam( list, script, "dup_x2" );
         }
         rule.setTestParameters( list );
         return list;
@@ -183,5 +184,18 @@ public class ArrayOperations extends AbstractBaseTest {
             crc.update( a );
             return crc.getValue();
         }
+
+        @Export
+        static int dup_x2() {
+            Object[] data = {null,null,null};
+            int index = 1;
+            Object value = null;
+
+            if ((data[index] = value) != null) { // test for instruction dup_x2
+                return 1;
+            } else {
+                return 2;
+            }
+        }
     }
 }