String concat const folding

OpenDreamProject · Oct 25, 2024 · d285143 · d285143
1 parent b974c59
commit d285143
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Showing 3 changed files with 32 additions and 7 deletions.
diff --git a/DMCompiler/DM/Builders/DMASTFolder.cs b/DMCompiler/DM/Builders/DMASTFolder.cs
@@ -254,13 +254,6 @@ private DMASTExpression FoldExpression(DMASTExpression? expression) {
 
                 break;
             }
-            case DMASTAdd add: {
-                DMASTConstantString? lhsString = add.LHS as DMASTConstantString;
-                DMASTConstantString? rhsString = add.RHS as DMASTConstantString;
-                if (lhsString != null && rhsString != null) return new DMASTConstantString(expression.Location, lhsString.Value + rhsString.Value);
-
-                break;
-            }
 
             #endregion Math
 

diff --git a/DMCompiler/Optimizer/AnnotatedBytecode.cs b/DMCompiler/Optimizer/AnnotatedBytecode.cs
@@ -249,6 +249,10 @@ public void SetLocation(Location loc) {
     public Location GetLocation() {
         return Location;
     }
+
+    public string ResolveString() {
+        return DMObjectTree.StringTable[Id];
+    }
 }
 
 internal sealed class AnnotatedBytecodeArgumentType : IAnnotatedBytecode {

diff --git a/DMCompiler/Optimizer/PeepholeOptimizations.cs b/DMCompiler/Optimizer/PeepholeOptimizations.cs
@@ -1,4 +1,5 @@
 using DMCompiler.Bytecode;
+using DMCompiler.DM;
 
 namespace DMCompiler.Optimizer;
 
@@ -678,6 +679,33 @@ public void Apply(List<IAnnotatedBytecode> input, int index) {
     }
 }
 
+// PushString [constant]
+// PushString [constant]
+// Add
+// -> PushString [result]
+internal sealed class ConstFoldAddStrings : IPeepholeOptimization {
+    public ReadOnlySpan<DreamProcOpcode> GetOpcodes() {
+        return [
+            DreamProcOpcode.PushString,
+            DreamProcOpcode.PushString,
+            DreamProcOpcode.Add,
+        ];
+    }
+
+    public void Apply(List<IAnnotatedBytecode> input, int index) {
+        var firstInstruction = (AnnotatedBytecodeInstruction)input[index];
+        var firstString = firstInstruction.GetArg<AnnotatedBytecodeString>(0);
+        var secondString = ((AnnotatedBytecodeInstruction)input[index+1]).GetArg<AnnotatedBytecodeString>(0);
+
+        var combinedId = DMObjectTree.AddString(firstString.ResolveString() + secondString.ResolveString());
+
+        var args = new List<IAnnotatedBytecode>(1) {new AnnotatedBytecodeString(combinedId, firstInstruction.Location)};
+
+        IPeepholeOptimization.ReplaceInstructions(input, index, 3,
+            new AnnotatedBytecodeInstruction(DreamProcOpcode.PushString, 1, args));
+    }
+}
+
 // PushFloat [constant]
 // PushFloat [constant]
 // Subtract