remove swap

git-svn-id: https://svn.code.sf.net/p/jode/code/trunk@209 379699f6-c40d-0410-875b-85095c16579e

jode/jode/flow/SpecialBlock.java

@@ -17,6 +17,8 @@
  */
 package jode.flow;
 import jode.TabbedPrintWriter;
+import jode.Decompiler;
+import jode.decompiler.*;
 
 /**
  * This is the structured block for atomic instructions.
@@ -25,7 +27,8 @@ public class SpecialBlock extends StructuredBlock {
 
     public static int DUP  = 0;
     public static int SWAP = 1;
-    private static String[] output = { "DUP", "SWAP" };
+    public static int POP  = 2;
+    private static String[] output = { "DUP", "SWAP", "POP" };
 
     /**
      * The type, one of DUP or SWAP
@@ -58,7 +61,157 @@ public class SpecialBlock extends StructuredBlock {
     }
 
     public boolean doTransformations() {
-        return type == SWAP
-            && RemoveEmpty.removeSwap(this, flowBlock.lastModified);
+        return (type == SWAP && removeSwap(flowBlock.lastModified))
+	    || (type == POP && removePop(flowBlock.lastModified));
+    }
+
+    public boolean removeSwap(StructuredBlock last) {
+
+        /* Remove non needed swaps; convert:
+         *
+         *   PUSH expr1
+         *   PUSH expr2
+         *   SWAP
+         *
+         * to:
+         *
+         *   PUSH expr2
+         *   PUSH expr1
+         */
+        if (last.outer instanceof SequentialBlock
+            && last.outer.outer instanceof SequentialBlock
+            && last.outer.getSubBlocks()[0] instanceof InstructionBlock
+            && last.outer.outer.getSubBlocks()[0] 
+            instanceof InstructionBlock) {
+
+            InstructionBlock block1 
+                = (InstructionBlock) last.outer.outer.getSubBlocks()[0];
+            InstructionBlock block2
+                = (InstructionBlock) last.outer.getSubBlocks()[0];
+
+	    Expression expr1 = block1.getInstruction();
+	    Expression expr2 = block2.getInstruction();
+
+            if (expr1.isVoid() || expr2.isVoid()
+		|| expr1.getOperandCount() != 0
+		|| expr2.getOperandCount() != 0
+		|| expr1.hasSideEffects(expr2) 
+		|| expr2.hasSideEffects(expr1))
+                return false;
+
+            /* PUSH expr1 == block1
+             * PUSH expr2
+             * SWAP
+             * ...
+             */
+            last.outer.replace(block1.outer);
+            /* PUSH expr2
+             * SWAP
+             * ...
+             */
+            block1.replace(this);
+            block1.moveJump(jump);
+            /* PUSH expr2
+             * PUSH expr1
+             */
+            block1.flowBlock.lastModified = block1;
+            return true;
+        }
+        return false;
+    }
+
+    public boolean removePop(StructuredBlock last) {
+
+	/* There are three possibilities:
+         *
+         *   PUSH method_invocation()
+         *   POP[sizeof PUSH]
+         * to:
+         *   method_invocation()
+	 *
+	 *   PUSH arg1
+	 *   PUSH arg2
+	 *   POP2
+	 * to:
+	 *   if (arg1 == arg2)
+	 *     empty
+	 *
+	 *   PUSH arg1
+	 *   POP
+	 * to:
+	 *   if (arg1 != 0)
+	 *     empty 
+         */
+
+        if (last.outer instanceof SequentialBlock
+	    && last.outer.getSubBlocks()[0] instanceof InstructionBlock) {
+
+            InstructionBlock prev
+                = (InstructionBlock) last.outer.getSubBlocks()[0];
+	    Expression instr = prev.getInstruction();
+
+	    if (instr.getType().stackSize() == count) {
+		StructuredBlock newBlock;
+		if (instr.getOperator() instanceof InvokeOperator
+		    || instr.getOperator() instanceof ConstructorOperator) {
+		    ComplexExpression newExpr = new ComplexExpression
+			(new PopOperator(instr.getType()),
+			 new Expression[] { instr });
+		    prev.setInstruction(newExpr);
+		    newBlock = prev;
+		} else {
+		    ComplexExpression newCond = new ComplexExpression
+			(new CompareUnaryOperator(instr.getType(), 
+						  Operator.NOTEQUALS_OP), 
+			 new Expression[] { instr });
+		    IfThenElseBlock newIfThen = new IfThenElseBlock(newCond);
+		    newIfThen.setThenBlock(new EmptyBlock());
+		    newBlock = newIfThen;
+		}
+		newBlock.moveDefinitions(last.outer, newBlock);
+		newBlock.moveJump(jump);
+		if (this == last) {
+		    newBlock.replace(last.outer);
+		    flowBlock.lastModified = newBlock;
+		} else {
+		    newBlock.replace(this);
+		    last.replace(last.outer);
+		}
+		return true;
+	    } else if (last.outer.outer instanceof SequentialBlock
+		       && (last.outer.outer.getSubBlocks()[0] 
+			   instanceof InstructionBlock)) {
+		InstructionBlock prevprev
+		    = (InstructionBlock) last.outer.outer.getSubBlocks()[0];
+		Expression previnstr = prevprev.getInstruction();
+		if (previnstr.getType().stackSize() == 1 
+		    && instr.getType().stackSize() == 1
+		    && count == 2) {
+		    /* compare two objects */
+
+		    ComplexExpression newCond = new ComplexExpression
+			(new CompareBinaryOperator(instr.getType(), 
+						   Operator.EQUALS_OP), 
+			 new Expression[] { previnstr, instr });
+		    ConditionalBlock newIfThen = new ConditionalBlock(newCond);
+		    newIfThen.moveDefinitions(last.outer.outer, newIfThen);
+		    newIfThen.trueBlock.copyJump(jump);
+		    newIfThen.moveJump(jump);
+		    if (this == last) {
+			newIfThen.replace(last.outer.outer);
+			flowBlock.lastModified = newIfThen;
+		    } else {
+			newIfThen.replace(this);
+			last.replace(last.outer.outer);
+		    }
+		    return true;
+		}
+	    }
+        }
+        return false;
     }
 }
+
+
+
+