From 40375316e2aab269be9f3ce61c973872b40c8fdf Mon Sep 17 00:00:00 2001
From: Volker Berlin <volker.berlin@googlemail.com>
Date: Wed, 25 Sep 2019 19:24:01 +0200
Subject: [PATCH] detect some optimization of GOTO jumps

---
 .../jwebassembly/module/BranchManger.java        |  8 ++++++++
 .../runtime/ControlFlowOperators.java            | 16 ++++++++++++++++
 2 files changed, 24 insertions(+)

diff --git a/src/de/inetsoftware/jwebassembly/module/BranchManger.java b/src/de/inetsoftware/jwebassembly/module/BranchManger.java
index e3d1760..3119eb8 100644
--- a/src/de/inetsoftware/jwebassembly/module/BranchManger.java
+++ b/src/de/inetsoftware/jwebassembly/module/BranchManger.java
@@ -186,6 +186,14 @@ class BranchManger {
                                 convertToLoop( parsedBlock, conditionStart, conditionEnd );
                                 allParsedOperations.remove( n );
                                 ((IfParsedBlock)nextBlock).negateCompare();
+
+                                // if conditions that point at the end of the loop for optimization must now point at start.
+                                for( n = b - 1; n >= 0; n-- ) {
+                                    ParsedBlock prevBlock = allParsedOperations.get( n );
+                                    if( prevBlock.op == JavaBlockOperator.IF && prevBlock.endPosition == conditionStart ) {
+                                        prevBlock.endPosition = parsedBlock.startPosition;
+                                    }
+                                }
                                 break;
                             }
                             if( nextBlock.op == JavaBlockOperator.GOTO && nextBlock.endPosition == nextPos && n > 1 ) { // Eclipse loop with wide goto_w
diff --git a/test/de/inetsoftware/jwebassembly/runtime/ControlFlowOperators.java b/test/de/inetsoftware/jwebassembly/runtime/ControlFlowOperators.java
index 0e46a68..a7a2d63 100644
--- a/test/de/inetsoftware/jwebassembly/runtime/ControlFlowOperators.java
+++ b/test/de/inetsoftware/jwebassembly/runtime/ControlFlowOperators.java
@@ -70,6 +70,7 @@ public class ControlFlowOperators extends AbstractBaseTest {
             addParam( list, script, "ifAndOr4" );
             addParam( list, script, "ifAndOr6" );
             addParam( list, script, "ifAndOr8" );
+            addParam( list, script, "ifWithoutElseAndLoop" );
         }
         rule.setTestParameters( list );
         return list;
@@ -449,5 +450,20 @@ public class ControlFlowOperators extends AbstractBaseTest {
             }
             return result;
         }
+
+        private static int ifWithoutElseAndLoop;
+
+        @Export
+        static int ifWithoutElseAndLoop() {
+            int n = 1;
+            // because some compiler (Eclipse) move the loop condition to the end of the loop. Then there can be an optimization that the if jump to the end of the loop.
+            if( ifWithoutElseAndLoop != 1 ) {
+                ifWithoutElseAndLoop = 1;
+            }
+            while( n < 10 ) {
+                ifWithoutElseAndLoop *= n++;
+            }
+            return ifWithoutElseAndLoop;
+        }
     }
 }