Additional label optimization

DMCompiler/Optimizer/BytecodeOptimizer.cs

@@ -12,8 +12,17 @@
         RemoveUnreferencedLabels(input);
         JoinAndForwardLabels(input);
         RemoveUnreferencedLabels(input);
+        RemoveImmediateJumps(input);
+        RemoveUnreferencedLabels(input);
 
         _peepholeOptimizer.RunPeephole(input);
+
+        // Run label optimizations again due to possibly removed jumps in peephole optimizers
+        RemoveUnreferencedLabels(input);
+        JoinAndForwardLabels(input);
+        RemoveUnreferencedLabels(input);
+        RemoveImmediateJumps(input);
+        RemoveUnreferencedLabels(input);
     }
 
     private void RemoveUnreferencedLabels(List<IAnnotatedBytecode> input) {
@@ -40,6 +49,24 @@
         }
     }
 
+    /**
+     * <summary>Removes jumps for which the next element is the jump's destination</summary>
+     */
+    private void RemoveImmediateJumps(List<IAnnotatedBytecode> input) {
+        Dictionary<string, int> labelReferences = new();
+        for (int i = input.Count-2; i >= 0; i--) {
+            IAnnotatedBytecode curCode = input[i];
+            if (curCode is AnnotatedBytecodeInstruction instruction && instruction.Opcode == Bytecode.DreamProcOpcode.Jump) {
+                if (input[i+1] is AnnotatedBytecodeLabel followingLabel) {
+                    AnnotatedBytecodeLabel jumpLabelName = instruction.GetArg<AnnotatedBytecodeLabel>(0);
+                    if (jumpLabelName.LabelName == followingLabel.LabelName) {
+                        input.RemoveAt(i);
+                    }
+                }
+            }
+        }
+    }
+
     private void JoinAndForwardLabels(List<IAnnotatedBytecode> input) {
         Dictionary<string, string> labelAliases = new();
         for (int i = 0; i < input.Count; i++) {