fix: additional checks before insert move to help type inference (#843)

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

@@ -208,7 +208,7 @@ public class MethodNode extends LineAttrNode implements ILoadable, ICodeNode {
 			}
 			return argsTypes;
 		} catch (Exception e) {
-			addWarningComment("Failed to parse method signature: " + sp.getSignature(), e);
+			addWarnComment("Failed to parse method signature: " + sp.getSignature(), e);
 			return null;
 		}
 	}
@@ -698,11 +698,11 @@ public class MethodNode extends LineAttrNode implements ILoadable, ICodeNode {
 		ErrorsCounter.methodWarn(this, warnStr);
 	}
 
-	public void addWarningComment(String warn) {
-		addWarningComment(warn, null);
+	public void addWarnComment(String warn) {
+		addWarnComment(warn, null);
 	}
 
-	public void addWarningComment(String warn, @Nullable Throwable exc) {
+	public void addWarnComment(String warn, @Nullable Throwable exc) {
 		String commentStr = "JADX WARN: " + warn;
 		addAttr(AType.COMMENTS, commentStr);
 		if (exc != null) {

jadx-core/src/main/java/jadx/core/dex/visitors/debuginfo/DebugInfoApplyVisitor.java

@@ -64,7 +64,7 @@ public class DebugInfoApplyVisitor extends AbstractVisitor {
 		mth.getSVars().forEach(var -> {
 			ArgType type = var.getTypeInfo().getType();
 			if (!type.isTypeKnown()) {
-				mth.addComment("JADX WARNING: type inference failed for: " + var.getDetailedVarInfo(mth));
+				mth.addWarnComment("Type inference failed for: " + var.getDetailedVarInfo(mth));
 			}
 		});
 	}

jadx-core/src/main/java/jadx/core/dex/visitors/typeinference/TypeInferenceVisitor.java

@@ -72,7 +72,9 @@ public final class TypeInferenceVisitor extends AbstractVisitor {
 		if (!resolved) {
 			boolean moveAdded = false;
 			for (SSAVar var : new ArrayList<>(mth.getSVars())) {
-				moveAdded |= tryInsertAdditionalInsn(mth, var);
+				if (tryInsertAdditionalInsn(mth, var)) {
+					moveAdded = true;
+				}
 			}
 			if (moveAdded) {
 				InitCodeVariables.rerun(mth);
@@ -361,50 +363,67 @@ public final class TypeInferenceVisitor extends AbstractVisitor {
 			}
 		}
 		for (PhiInsn phiInsn : usedInPhiList) {
-			if (!insertMoveForPhi(mth, phiInsn, var)) {
+			if (!insertMoveForPhi(mth, phiInsn, var, false)) {
 				return false;
 			}
 		}
+
+		// all check passed => apply
+		for (PhiInsn phiInsn : usedInPhiList) {
+			insertMoveForPhi(mth, phiInsn, var, true);
+		}
+		mth.addComment("JADX INFO: additional move instructions added (" + usedInPhiList.size() + ") to help type inference");
 		return true;
 	}
 
-	private boolean insertMoveForPhi(MethodNode mth, PhiInsn phiInsn, SSAVar var) {
+	private boolean insertMoveForPhi(MethodNode mth, PhiInsn phiInsn, SSAVar var, boolean apply) {
 		int argsCount = phiInsn.getArgsCount();
 		for (int argIndex = 0; argIndex < argsCount; argIndex++) {
 			RegisterArg reg = phiInsn.getArg(argIndex);
 			if (reg.getSVar() == var) {
-				BlockNode blockNode = phiInsn.getBlockByArgIndex(argIndex);
-				InsnNode lastInsn = BlockUtils.getLastInsn(blockNode);
-				if (lastInsn != null && BlockSplitter.isSeparate(lastInsn.getType())) {
-					// can't insert move in block with separate instruction
-					// trying previous block
-					List<BlockNode> preds = blockNode.getPredecessors();
-					if (preds.size() == 1) {
-						blockNode = preds.get(0);
-					} else {
-						mth.addWarn("Failed to insert additional move for type inference");
-						return false;
-					}
+				BlockNode startBlock = phiInsn.getBlockByArgIndex(argIndex);
+				BlockNode blockNode = checkBlockForInsnInsert(startBlock);
+				if (blockNode == null) {
+					mth.addWarnComment("Failed to insert an additional move for type inference into block " + startBlock);
+					return false;
+				}
+				if (apply) {
+					int regNum = reg.getRegNum();
+					RegisterArg resultArg = reg.duplicate(regNum, null);
+					SSAVar newSsaVar = mth.makeNewSVar(regNum, resultArg);
+					RegisterArg arg = reg.duplicate(regNum, var);
+
+					InsnNode moveInsn = new InsnNode(InsnType.MOVE, 1);
+					moveInsn.setResult(resultArg);
+					moveInsn.addArg(arg);
+					moveInsn.add(AFlag.SYNTHETIC);
+					blockNode.getInstructions().add(moveInsn);
+
+					phiInsn.replaceArg(reg, reg.duplicate(regNum, newSsaVar));
 				}
-
-				int regNum = reg.getRegNum();
-				RegisterArg resultArg = reg.duplicate(regNum, null);
-				SSAVar newSsaVar = mth.makeNewSVar(regNum, resultArg);
-				RegisterArg arg = reg.duplicate(regNum, var);
-
-				InsnNode moveInsn = new InsnNode(InsnType.MOVE, 1);
-				moveInsn.setResult(resultArg);
-				moveInsn.addArg(arg);
-				moveInsn.add(AFlag.SYNTHETIC);
-				blockNode.getInstructions().add(moveInsn);
-
-				phiInsn.replaceArg(reg, reg.duplicate(regNum, newSsaVar));
 				return true;
 			}
 		}
 		return false;
 	}
 
+	@Nullable
+	private BlockNode checkBlockForInsnInsert(BlockNode blockNode) {
+		if (blockNode.isSynthetic()) {
+			return null;
+		}
+		InsnNode lastInsn = BlockUtils.getLastInsn(blockNode);
+		if (lastInsn != null && BlockSplitter.isSeparate(lastInsn.getType())) {
+			// can't insert move in a block with 'separate' instruction => try previous block by simple path
+			List<BlockNode> preds = blockNode.getPredecessors();
+			if (preds.size() == 1) {
+				return checkBlockForInsnInsert(preds.get(0));
+			}
+			return null;
+		}
+		return blockNode;
+	}
+
 	private boolean tryWiderObjects(MethodNode mth, SSAVar var) {
 		Set<ArgType> objTypes = new LinkedHashSet<>();
 		for (ITypeBound bound : var.getTypeInfo().getBounds()) {