Fix stack type of comparison operations

UnderminersTeam · Jul 1, 2024 · 94942e1 · 94942e1
1 parent 6f5816e
commit 94942e1
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Showing 2 changed files with 48 additions and 7 deletions.
diff --git a/Underanalyzer/Decompiler/AST/Nodes/BinaryNode.cs b/Underanalyzer/Decompiler/AST/Nodes/BinaryNode.cs
@@ -43,17 +43,25 @@ public BinaryNode(IExpressionNode left, IExpressionNode right, IGMInstruction in
         Right = right;  
         Instruction = instruction;
 
-        // Type1 and Type2 on the instruction represent the data types of Left and Right on the stack.
-        // Choose whichever type has a higher bias, or if equal, the smaller numerical data type value.
-        int bias1 = StackTypeBias(instruction.Type1);
-        int bias2 = StackTypeBias(instruction.Type2);
-        if (bias1 == bias2)
+        if (Instruction.Kind == Opcode.Compare)
         {
-            StackType = (DataType)Math.Min((byte)instruction.Type1, (byte)instruction.Type2);
+            // For comparison operations, the result is always a boolean.
+            StackType = DataType.Boolean;
         }
         else
         {
-            StackType = (bias1 > bias2) ? instruction.Type1 : instruction.Type2;
+            // Type1 and Type2 on the instruction represent the data types of Left and Right on the stack.
+            // Choose whichever type has a higher bias, or if equal, the smaller numerical data type value.
+            int bias1 = StackTypeBias(instruction.Type1);
+            int bias2 = StackTypeBias(instruction.Type2);
+            if (bias1 == bias2)
+            {
+                StackType = (DataType)Math.Min((byte)instruction.Type1, (byte)instruction.Type2);
+            }
+            else
+            {
+                StackType = (bias1 > bias2) ? instruction.Type1 : instruction.Type2;
+            }
         }
     }
 

diff --git a/UnderanalyzerTest/DecompileContext.DecompileToString.cs b/UnderanalyzerTest/DecompileContext.DecompileToString.cs
@@ -2070,4 +2070,37 @@ bf [end]
             """
         );
     }
+
+    [Fact]
+    public void TestBooleanSwitch()
+    {
+        TestUtil.VerifyDecompileResult(
+            """
+            :[0]
+            push.v builtin.a
+            push.v builtin.b
+            cmp.v.v LT
+            dup.b 0
+            pushi.e 0
+            cmp.i.b EQ
+            bt [2]
+
+            :[1]
+            b [3]
+
+            :[2]
+            b [3]
+
+            :[3]
+            popz.b
+            """,
+            """
+            switch (a < b)
+            {
+                case 0:
+                    break;
+            }
+            """
+        );
+    }
 }