Fix array assign ppmm bug

Author: Kroppeb

src/org/jetbrains/java/decompiler/modules/decompiler/SimplifyExprentsHelper.java

@@ -729,8 +729,12 @@ private static Pair<Exprent, VarExprent> findFirstValidUsage(VarExprent match, E
       for (int i = exprents.size() - 1; i >= 0; i--) {
         Exprent ex = exprents.get(i);
 
-        // Skip LHS of assignment as it is invalid
-        if (expr instanceof AssignmentExprent asExpr && ex == asExpr.getLeft()) {
+        // Avoid making something like `++a = 5`. It shouldn't happen but better be safe than sorry.
+        if (expr instanceof AssignmentExprent asExpr &&
+          ex == asExpr.getLeft() &&
+          ex instanceof VarExprent innerEx &&
+          innerEx.getIndex() == match.getIndex()
+        ) {
           continue;
         }
 

testData/results/pkg/TestArrayPPMM.dec

@@ -38,11 +38,11 @@ public class TestArrayPPMM {
    }// 40
 
    public void test9(int[] array, int i) {
-      array[i] = ++i;// 43
+      array[++i] = i;// 43
    }// 44
 
    public void test10(int i) {
-      this.getArray()[i] = ++i;// 47
+      this.getArray()[++i] = i;// 47
    }// 48
 
    private void accept(int i, int j) {
@@ -207,7 +207,7 @@ class 'pkg/TestArrayPPMM' {
       1      40
       2      40
       3      40
-      4      40
+      5      40
       6      40
       7      41
    }
@@ -220,7 +220,7 @@ class 'pkg/TestArrayPPMM' {
       4      44
       5      44
       6      44
-      7      44
+      8      44
       9      44
       a      45
    }

testData/results/pkg/TestPPMM.dec

@@ -82,11 +82,44 @@ public class TestPPMM {
       t2(a, a);// 98
    }// 99
 
+   public void ppiAssign() {
+      int a = 0;// 102
+      a++;// 103
+      a = 5;// 104
+      System.out.println();// 105
+      a = ++a + 5;// 106 107
+      System.out.println();// 108
+      a = 5 * ++a;// 109 110
+      System.out.println();// 111
+      t(a);// 112
+   }// 113
+
+   public void ppiAssignPhi(boolean b) {
+      int a = 0;// 117
+      if (b) {// 118
+         a++;// 119
+         a = 5;// 120
+      }
+
+      System.out.println();// 122
+      if (b) {// 123
+         a = ++a + 5;// 124 125
+      }
+
+      System.out.println();// 127
+      if (b) {// 128
+         a = 5 * ++a;// 129 130
+      }
+
+      System.out.println();// 132
+      t(a);// 133
+   }// 134
+
    private static void t(int x) {
-   }// 102
+   }// 137
 
    private static void t2(int x, int y) {
-   }// 106
+   }// 141
 }
 
 class 'pkg/TestPPMM' {
@@ -375,12 +408,114 @@ class 'pkg/TestPPMM' {
       66      82
    }
 
-   method 't (I)V' {
+   method 'ppiAssign ()V' {
       0      85
+      1      85
+      2      86
+      3      86
+      4      86
+      5      87
+      6      87
+      7      88
+      8      88
+      9      88
+      a      88
+      b      88
+      c      88
+      d      89
+      e      89
+      f      89
+      11      89
+      12      89
+      13      89
+      14      90
+      15      90
+      16      90
+      17      90
+      18      90
+      19      90
+      1a      91
+      1b      91
+      1c      91
+      1d      91
+      1f      91
+      20      91
+      21      92
+      22      92
+      23      92
+      24      92
+      25      92
+      26      92
+      27      93
+      28      93
+      29      93
+      2a      93
+      2b      94
+   }
+
+   method 'ppiAssignPhi (Z)V' {
+      0      97
+      1      97
+      2      98
+      3      98
+      4      98
+      5      98
+      6      99
+      7      99
+      8      99
+      9      100
+      a      100
+      b      103
+      c      103
+      d      103
+      e      103
+      f      103
+      10      103
+      11      104
+      12      104
+      13      104
+      14      104
+      15      105
+      16      105
+      17      105
+      19      105
+      1a      105
+      1b      105
+      1c      108
+      1d      108
+      1e      108
+      1f      108
+      20      108
+      21      108
+      22      109
+      23      109
+      24      109
+      25      109
+      26      110
+      27      110
+      28      110
+      29      110
+      2b      110
+      2c      110
+      2d      113
+      2e      113
+      2f      113
+      30      113
+      31      113
+      32      113
+      33      114
+      34      114
+      35      114
+      36      114
+      37      115
+   }
+
+   method 't (I)V' {
+      0      118
    }
 
    method 't2 (II)V' {
-      0      88
+      0      121
    }
 }
 
@@ -454,4 +589,31 @@ Lines mapping:
 98 <-> 82
 99 <-> 83
 102 <-> 86
-106 <-> 89
+103 <-> 87
+104 <-> 88
+105 <-> 89
+106 <-> 90
+107 <-> 90
+108 <-> 91
+109 <-> 92
+110 <-> 92
+111 <-> 93
+112 <-> 94
+113 <-> 95
+117 <-> 98
+118 <-> 99
+119 <-> 100
+120 <-> 101
+122 <-> 104
+123 <-> 105
+124 <-> 106
+125 <-> 106
+127 <-> 109
+128 <-> 110
+129 <-> 111
+130 <-> 111
+132 <-> 114
+133 <-> 115
+134 <-> 116
+137 <-> 119
+141 <-> 122

testData/src/java8/pkg/TestPPMM.java

@@ -98,6 +98,41 @@ public void doubleppi() {
       t2(a, a);
    }
 
+   public void ppiAssign() {
+      int a = 0;
+      ++a;
+      a = 5;
+      System.out.println();
+      ++a;
+      a = a + 5;
+      System.out.println();
+      ++a;
+      a = 5 * a;
+      System.out.println();
+      t(a);
+   }
+
+
+  public void ppiAssignPhi(boolean b) {
+    int a = 0;
+    if (b) {
+      ++a;
+      a = 5;
+    }
+    System.out.println();
+    if (b) {
+      ++a;
+      a = a + 5;
+    }
+    System.out.println();
+    if (b) {
+      ++a;
+      a = 5 * a;
+    }
+    System.out.println();
+    t(a);
+  }
+
    private static void t(int x){
    }