core: move same instructions from predecessors for loops

jadx-core/src/main/java/jadx/core/dex/attributes/AttrNode.java

@@ -96,4 +96,8 @@ public abstract class AttrNode implements IAttributeNode {
 	public String getAttributesString() {
 		return storage.toString();
 	}
+
+	public boolean isAttrStorageEmpty() {
+		return storage.isEmpty();
+	}
 }

jadx-core/src/main/java/jadx/core/dex/nodes/InsnNode.java

@@ -4,6 +4,7 @@ import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Collections;
 import java.util.List;
+import java.util.Objects;
 
 import com.android.dx.io.instructions.DecodedInstruction;
 import com.rits.cloning.Cloner;
@@ -251,12 +252,14 @@ public class InsnNode extends LineAttrNode {
 		if (this == other) {
 			return true;
 		}
-		if (insnType != other.insnType
-				|| arguments.size() != other.arguments.size()) {
+		if (insnType != other.insnType) {
 			return false;
 		}
-		// check wrapped instructions
 		int size = arguments.size();
+		if (size != other.arguments.size()) {
+			return false;
+		}
+		// check wrapped instructions
 		for (int i = 0; i < size; i++) {
 			InsnArg arg = arguments.get(i);
 			InsnArg otherArg = other.arguments.get(i);
@@ -273,6 +276,16 @@ public class InsnNode extends LineAttrNode {
 		}
 		return true;
 	}
+	/**
+	 * 'Hard' equals, compare all arguments
+	 */
+	public boolean isDeepEquals(InsnNode other) {
+		if (this == other) {
+			return true;
+		}
+		return isSame(other)
+				&& Objects.equals(arguments, other.arguments);
+	}
 
 	protected <T extends InsnNode> T copyCommonParams(T copy) {
 		copy.setResult(result);

jadx-core/src/main/java/jadx/core/dex/visitors/blocksmaker/BlockProcessor.java

@@ -45,6 +45,10 @@ public class BlockProcessor extends AbstractVisitor {
 
 	private static void processBlocksTree(MethodNode mth) {
 		computeDominators(mth);
+		if (independentBlockTreeMod(mth)) {
+			clearBlocksState(mth);
+			computeDominators(mth);
+		}
 		markReturnBlocks(mth);
 
 		int i = 0;
@@ -64,6 +68,109 @@ public class BlockProcessor extends AbstractVisitor {
 		processNestedLoops(mth);
 	}
 
+	private static boolean removeEmptyBlock(MethodNode mth, BlockNode block) {
+		if (block.getInstructions().isEmpty()
+				&& !block.isSynthetic()
+				&& block.isAttrStorageEmpty()
+				&& block.getSuccessors().size() <= 1) {
+			LOG.debug("Removing empty block: {}", block);
+			if (block.getSuccessors().size() == 1) {
+				BlockNode successor = block.getSuccessors().get(0);
+				block.getPredecessors().forEach(pred -> {
+					pred.getSuccessors().remove(block);
+					BlockSplitter.connect(pred, successor);
+					BlockSplitter.replaceTarget(pred, block, successor);
+					pred.updateCleanSuccessors();
+				});
+				BlockSplitter.removeConnection(block, successor);
+			} else {
+				block.getPredecessors().forEach(pred -> {
+					pred.getSuccessors().remove(block);
+					pred.updateCleanSuccessors();
+				});
+			}
+			block.add(AFlag.REMOVE);
+			block.getSuccessors().clear();
+			block.getPredecessors().clear();
+			return true;
+		}
+		return false;
+	}
+
+	private static boolean deduplicateBlockInsns(BlockNode block) {
+		if (block.contains(AFlag.LOOP_START) || block.contains(AFlag.LOOP_END)) {
+			// search for same instruction at end of all predecessors blocks
+			List<BlockNode> predecessors = block.getPredecessors();
+			int predsCount = predecessors.size();
+			if (predsCount > 1) {
+				InsnNode lastInsn = BlockUtils.getLastInsn(block);
+				if (lastInsn != null && lastInsn.getType() == InsnType.IF) {
+					return false;
+				}
+				int sameInsnCount = getSameLastInsnCount(predecessors);
+				if (sameInsnCount > 0) {
+					List<InsnNode> insns = getLastInsns(predecessors.get(0), sameInsnCount);
+					insertAtStart(block, insns);
+					predecessors.forEach(pred -> getLastInsns(pred, sameInsnCount).clear());
+					LOG.debug("Move duplicate insns, count: {} to block {}", sameInsnCount, block);
+					return true;
+				}
+			}
+		}
+		return false;
+	}
+
+	private static List<InsnNode> getLastInsns(BlockNode blockNode, int sameInsnCount) {
+		List<InsnNode> instructions = blockNode.getInstructions();
+		int size = instructions.size();
+		return instructions.subList(size - sameInsnCount, size);
+	}
+
+	private static void insertAtStart(BlockNode block, List<InsnNode> insns) {
+		List<InsnNode> blockInsns = block.getInstructions();
+
+		List<InsnNode> newInsnList = new ArrayList<>(insns.size() + blockInsns.size());
+		newInsnList.addAll(insns);
+		newInsnList.addAll(blockInsns);
+
+		blockInsns.clear();
+		blockInsns.addAll(newInsnList);
+	}
+
+	private static int getSameLastInsnCount(List<BlockNode> predecessors) {
+		int sameInsnCount = 0;
+		while (true) {
+			InsnNode insn = null;
+			for (BlockNode pred : predecessors) {
+				InsnNode curInsn = getInsnsFromEnd(pred, sameInsnCount);
+				if (curInsn == null) {
+					return sameInsnCount;
+				}
+				if (insn == null) {
+					insn = curInsn;
+				} else {
+					if (!isSame(insn, curInsn)) {
+						return sameInsnCount;
+					}
+				}
+			}
+			sameInsnCount++;
+		}
+	}
+
+	private static boolean isSame(InsnNode insn, InsnNode curInsn) {
+		return /*insn.getType() == InsnType.MOVE &&*/ insn.isDeepEquals(curInsn) && insn.canReorder();
+	}
+
+	private static InsnNode getInsnsFromEnd(BlockNode block, int number) {
+		List<InsnNode> instructions = block.getInstructions();
+		int insnCount = instructions.size();
+		if (insnCount <= number) {
+			return null;
+		}
+		return instructions.get(insnCount - number - 1);
+	}
+
 	private static void computeDominators(MethodNode mth) {
 		List<BlockNode> basicBlocks = mth.getBasicBlocks();
 		int nBlocks = basicBlocks.size();
@@ -104,9 +211,7 @@ public class BlockProcessor extends AbstractVisitor {
 		markLoops(mth);
 
 		// clear self dominance
-		for (BlockNode block : basicBlocks) {
-			block.getDoms().clear(block.getId());
-		}
+		basicBlocks.forEach(block -> block.getDoms().clear(block.getId()));
 
 		// calculate immediate dominators
 		for (BlockNode block : basicBlocks) {
@@ -148,9 +253,7 @@ public class BlockProcessor extends AbstractVisitor {
 		if (block.getDomFrontier() != null) {
 			return;
 		}
-		for (BlockNode c : block.getDominatesOn()) {
-			computeBlockDF(mth, c);
-		}
+		block.getDominatesOn().forEach(c -> computeBlockDF(mth, c));
 		List<BlockNode> blocks = mth.getBasicBlocks();
 		BitSet domFrontier = null;
 		for (BlockNode s : block.getSuccessors()) {
@@ -180,39 +283,37 @@ public class BlockProcessor extends AbstractVisitor {
 
 	private static void markReturnBlocks(MethodNode mth) {
 		mth.getExitBlocks().clear();
-		for (BlockNode block : mth.getBasicBlocks()) {
+		mth.getBasicBlocks().forEach(block -> {
 			if (BlockUtils.checkLastInsnType(block, InsnType.RETURN)) {
 				block.add(AFlag.RETURN);
 				mth.getExitBlocks().add(block);
 			}
-		}
+		});
 	}
 
 	private static void markLoops(MethodNode mth) {
-		for (BlockNode block : mth.getBasicBlocks()) {
-			for (BlockNode succ : block.getSuccessors()) {
-				// Every successor that dominates its predecessor is a header of a loop,
-				// block -> succ is a back edge.
-				if (block.getDoms().get(succ.getId())) {
-					succ.add(AFlag.LOOP_START);
+		mth.getBasicBlocks().forEach(block -> {
+			// Every successor that dominates its predecessor is a header of a loop,
+			// block -> succ is a back edge.
+			block.getSuccessors().forEach(successor -> {
+				if (block.getDoms().get(successor.getId())) {
+					successor.add(AFlag.LOOP_START);
 					block.add(AFlag.LOOP_END);
 
-					LoopInfo loop = new LoopInfo(succ, block);
-					succ.addAttr(AType.LOOP, loop);
+					LoopInfo loop = new LoopInfo(successor, block);
+					successor.addAttr(AType.LOOP, loop);
 					block.addAttr(AType.LOOP, loop);
 				}
-			}
-		}
+			});
+		});
 	}
 
 	private static void registerLoops(MethodNode mth) {
-		for (BlockNode block : mth.getBasicBlocks()) {
+		mth.getBasicBlocks().forEach(block -> {
 			if (block.contains(AFlag.LOOP_START)) {
-				for (LoopInfo loop : block.getAll(AType.LOOP)) {
-					mth.registerLoop(loop);
-				}
+				block.getAll(AType.LOOP).forEach(mth::registerLoop);
 			}
-		}
+		});
 	}
 
 	private static void processNestedLoops(MethodNode mth) {
@@ -242,10 +343,14 @@ public class BlockProcessor extends AbstractVisitor {
 	}
 
 	private static boolean modifyBlocksTree(MethodNode mth) {
-		for (BlockNode block : mth.getBasicBlocks()) {
+		List<BlockNode> basicBlocks = mth.getBasicBlocks();
+		for (BlockNode block : basicBlocks) {
 			if (block.getPredecessors().isEmpty() && block != mth.getEnterBlock()) {
 				throw new JadxRuntimeException("Unreachable block: " + block);
 			}
+		}
+
+		for (BlockNode block : basicBlocks) {
 			if (checkLoops(mth, block)) {
 				return true;
 			}
@@ -253,6 +358,25 @@ public class BlockProcessor extends AbstractVisitor {
 		return splitReturn(mth);
 	}
 
+	private static boolean independentBlockTreeMod(MethodNode mth) {
+		List<BlockNode> basicBlocks = mth.getBasicBlocks();
+		boolean changed = false;
+		for (BlockNode basicBlock : basicBlocks) {
+			if (deduplicateBlockInsns(basicBlock)) {
+				changed = true;
+			}
+		}
+		for (BlockNode basicBlock : basicBlocks) {
+			if (removeEmptyBlock(mth, basicBlock)) {
+				changed = true;
+			}
+		}
+		if (BlockSplitter.removeEmptyDetachedBlocks(mth)) {
+			changed = true;
+		}
+		return changed;
+	}
+
 	private static boolean checkLoops(MethodNode mth, BlockNode block) {
 		// check loops
 		List<LoopInfo> loops = block.getAll(AType.LOOP);
@@ -303,9 +427,7 @@ public class BlockProcessor extends AbstractVisitor {
 						change = true;
 					}
 				}
-				if (change) {
-					return true;
-				}
+				return change;
 			}
 		}
 		return false;

jadx-core/src/main/java/jadx/core/dex/visitors/blocksmaker/BlockSplitter.java

@@ -253,8 +253,8 @@ public class BlockSplitter extends AbstractVisitor {
 		}
 	}
 
-	static void removeEmptyDetachedBlocks(MethodNode mth) {
-		mth.getBasicBlocks().removeIf(block ->
+	static boolean removeEmptyDetachedBlocks(MethodNode mth) {
+		return mth.getBasicBlocks().removeIf(block ->
 				block.getInstructions().isEmpty()
 						&& block.getPredecessors().isEmpty()
 						&& block.getSuccessors().isEmpty()