fix: inline move instructions to help process constructors (#927)

jadx-core/src/main/java/jadx/core/Jadx.java

@@ -58,6 +58,7 @@ public class Jadx {
 			passes.add(new BlockFinish());
 
 			passes.add(new SSATransform());
+			passes.add(new MoveInlineVisitor());
 			passes.add(new ConstructorVisitor());
 			passes.add(new InitCodeVariables());
 			passes.add(new MarkFinallyVisitor());

jadx-core/src/main/java/jadx/core/dex/instructions/args/RegisterArg.java

@@ -130,12 +130,20 @@ public class RegisterArg extends InsnArg implements Named {
 		return duplicate(getRegNum(), sVar);
 	}
 
+	public RegisterArg duplicate(ArgType initType) {
+		return duplicate(getRegNum(), initType, sVar);
+	}
+
 	public RegisterArg duplicate(@Nullable SSAVar ssaVar) {
 		return duplicate(getRegNum(), ssaVar);
 	}
 
 	public RegisterArg duplicate(int regNum, @Nullable SSAVar sVar) {
-		RegisterArg dup = new RegisterArg(regNum, getInitType());
+		return duplicate(regNum, getInitType(), sVar);
+	}
+
+	public RegisterArg duplicate(int regNum, ArgType initType, @Nullable SSAVar sVar) {
+		RegisterArg dup = new RegisterArg(regNum, initType);
 		if (sVar != null) {
 			// only 'set' here, 'assign' or 'use' will binds later
 			dup.setSVar(sVar);

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

@@ -217,6 +217,17 @@ public class InsnNode extends LineAttrNode {
 		}
 	}
 
+	public boolean canRemoveResult() {
+		switch (getType()) {
+			case INVOKE:
+			case CONSTRUCTOR:
+				return true;
+
+			default:
+				return false;
+		}
+	}
+
 	public boolean canReorder() {
 		if (contains(AFlag.DONT_GENERATE)) {
 			if (getType() == InsnType.MONITOR_EXIT) {

jadx-core/src/main/java/jadx/core/dex/visitors/ConstructorVisitor.java

@@ -24,7 +24,7 @@ import jadx.core.utils.InsnRemover;
 @JadxVisitor(
 		name = "ConstructorVisitor",
 		desc = "Replace invoke with constructor call",
-		runAfter = SSATransform.class,
+		runAfter = { SSATransform.class, MoveInlineVisitor.class },
 		runBefore = TypeInferenceVisitor.class
 )
 public class ConstructorVisitor extends AbstractVisitor {

jadx-core/src/main/java/jadx/core/dex/visitors/MoveInlineVisitor.java

+package jadx.core.dex.visitors;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import jadx.core.dex.attributes.AType;
+import jadx.core.dex.attributes.nodes.RegDebugInfoAttr;
+import jadx.core.dex.instructions.InsnType;
+import jadx.core.dex.instructions.args.InsnArg;
+import jadx.core.dex.instructions.args.RegisterArg;
+import jadx.core.dex.instructions.args.SSAVar;
+import jadx.core.dex.nodes.BlockNode;
+import jadx.core.dex.nodes.InsnNode;
+import jadx.core.dex.nodes.MethodNode;
+import jadx.core.dex.visitors.shrink.CodeShrinkVisitor;
+import jadx.core.dex.visitors.ssa.SSATransform;
+import jadx.core.utils.InsnRemover;
+
+@JadxVisitor(
+		name = "MoveInlineVisitor",
+		desc = "Inline redundant move instructions",
+		runAfter = SSATransform.class,
+		runBefore = CodeShrinkVisitor.class
+)
+public class MoveInlineVisitor extends AbstractVisitor {
+	@Override
+	public void visit(MethodNode mth) {
+		if (mth.isNoCode()) {
+			return;
+		}
+		moveInline(mth);
+	}
+
+	private static void moveInline(MethodNode mth) {
+		InsnRemover remover = new InsnRemover(mth);
+		for (BlockNode block : mth.getBasicBlocks()) {
+			remover.setBlock(block);
+			List<InsnNode> insns = block.getInstructions();
+			int size = insns.size();
+			for (int i = 0; i < size; i++) {
+				InsnNode insn = insns.get(i);
+				if (insn.getType() == InsnType.MOVE
+						&& processMove(mth, block, insn, i)) {
+					remover.addAndUnbind(insn);
+				}
+			}
+			remover.perform();
+		}
+	}
+
+	private static boolean processMove(MethodNode mth, BlockNode block, InsnNode move, int i) {
+		RegisterArg resultArg = move.getResult();
+		InsnArg moveArg = move.getArg(0);
+		if (resultArg.sameRegAndSVar(moveArg)) {
+			return true;
+		}
+		SSAVar ssaVar = resultArg.getSVar();
+		if (ssaVar.isUsedInPhi()) {
+			return false;
+		}
+		RegDebugInfoAttr debugInfo = resultArg.get(AType.REG_DEBUG_INFO);
+		for (RegisterArg useArg : ssaVar.getUseList()) {
+			InsnNode useInsn = useArg.getParentInsn();
+			if (useInsn == null || !fromThisBlock(block, useInsn, i)) {
+				return false;
+			}
+			RegDebugInfoAttr debugInfoAttr = useArg.get(AType.REG_DEBUG_INFO);
+			if (debugInfoAttr != null) {
+				debugInfo = debugInfoAttr;
+			}
+		}
+
+		// all checks passed, execute inline
+		for (RegisterArg useArg : new ArrayList<>(ssaVar.getUseList())) {
+			InsnNode useInsn = useArg.getParentInsn();
+			InsnArg replaceArg;
+			if (moveArg.isRegister()) {
+				replaceArg = ((RegisterArg) moveArg).duplicate(useArg.getInitType());
+			} else {
+				replaceArg = moveArg.duplicate();
+			}
+			replaceArg.copyAttributesFrom(useArg);
+			if (debugInfo != null) {
+				replaceArg.addAttr(debugInfo);
+			}
+			if (useInsn == null || !useInsn.replaceArg(useArg, replaceArg)) {
+				mth.addWarnComment("Failed to replace arg in insn: " + useInsn);
+			}
+		}
+		return true;
+	}
+
+	private static boolean fromThisBlock(BlockNode block, InsnNode insn, int curPos) {
+		List<InsnNode> list = block.getInstructions();
+		int size = list.size();
+		for (int j = curPos; j < size; j++) {
+			if (list.get(j) == insn) {
+				return true;
+			}
+		}
+		return false;
+	}
+}

jadx-core/src/main/java/jadx/core/dex/visitors/regions/variables/ProcessVariables.java

@@ -26,6 +26,7 @@ import jadx.core.dex.nodes.InsnNode;
 import jadx.core.dex.nodes.MethodNode;
 import jadx.core.dex.regions.loops.LoopRegion;
 import jadx.core.dex.visitors.AbstractVisitor;
+import jadx.core.dex.visitors.regions.AbstractRegionVisitor;
 import jadx.core.dex.visitors.regions.DepthRegionTraversal;
 import jadx.core.dex.visitors.typeinference.TypeCompare;
 import jadx.core.dex.visitors.typeinference.TypeCompareEnum;
@@ -41,6 +42,7 @@ public class ProcessVariables extends AbstractVisitor {
 		if (mth.isNoCode() || mth.getSVars().isEmpty()) {
 			return;
 		}
+		removeUnusedResults(mth);
 
 		List<CodeVar> codeVars = collectCodeVars(mth);
 		if (codeVars.isEmpty()) {
@@ -64,6 +66,24 @@ public class ProcessVariables extends AbstractVisitor {
 		}
 	}
 
+	private static void removeUnusedResults(MethodNode mth) {
+		DepthRegionTraversal.traverse(mth, new AbstractRegionVisitor() {
+			@Override
+			public void processBlock(MethodNode mth, IBlock container) {
+				for (InsnNode insn : container.getInstructions()) {
+					RegisterArg resultArg = insn.getResult();
+					if (resultArg != null) {
+						SSAVar ssaVar = resultArg.getSVar();
+						if (ssaVar.getUseList().isEmpty() && insn.canRemoveResult()) {
+							insn.setResult(null);
+							mth.removeSVar(ssaVar);
+						}
+					}
+				}
+			}
+		});
+	}
+
 	private void checkCodeVars(MethodNode mth, List<CodeVar> codeVars) {
 		int unknownTypesCount = 0;
 		for (CodeVar codeVar : codeVars) {

jadx-core/src/test/java/jadx/tests/integration/invoke/TestConstructorWithMoves.java

+package jadx.tests.integration.invoke;
+
+import org.junit.jupiter.api.Test;
+
+import jadx.tests.api.SmaliTest;
+
+import static jadx.tests.api.utils.assertj.JadxAssertions.assertThat;
+
+public class TestConstructorWithMoves extends SmaliTest {
+	// @formatter:off
+	/*
+		public boolean test() {
+				java.lang.Boolean r5 = new java.lang.Boolean
+				r8 = r5
+				r5 = r8
+				r6 = r8
+				java.lang.String r7 = "test"
+				r6.<init>(r7)
+				java.lang.Boolean r5 = (java.lang.Boolean) r5
+				boolean r5 = r5.booleanValue()
+				r3 = r5
+				return r3
+		}
+	*/
+	// @formatter:on
+
+	@Test
+	public void test() {
+		assertThat(getClassNodeFromSmali())
+				.code()
+				.containsOne("return new Boolean(\"test\").booleanValue();");
+	}
+}

jadx-core/src/test/smali/invoke/TestConstructorWithMoves.smali

+.class public Linvoke/TestConstructorWithMoves;
+.super Ljava/lang/Object;
+
+.method static public test()Z
+    .registers 11
+
+    new-instance v5, Ljava/lang/Boolean;
+    move-object v8, v5
+    move-object v5, v8
+    move-object v6, v8
+    const-string v7, "test"
+    invoke-direct {v6, v7}, Ljava/lang/Boolean;-><init>(Ljava/lang/String;)V
+    check-cast v5, Ljava/lang/Boolean;
+    invoke-virtual {v5}, Ljava/lang/Boolean;->booleanValue()Z
+    move-result v5
+    move v3, v5
+    return v3
+.end method
+