fix: keep wide upcast for arith instructions (#2730)

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

@@ -231,6 +231,9 @@ public class SimplifyVisitor extends AbstractVisitor {
 		}
 
 		ArgType castToType = (ArgType) castInsn.getIndex();
+		if (isArithWideUpCast(parentInsn, argType, castToType)) {
+			return null;
+		}
 		if (!ArgType.isCastNeeded(mth.root(), argType, castToType)
 				|| isCastDuplicate(castInsn)
 				|| shadowedByOuterCast(mth.root(), castToType, parentInsn)) {
@@ -243,6 +246,21 @@ public class SimplifyVisitor extends AbstractVisitor {
 		return null;
 	}
 
+	/**
+	 * Keep cast to wide types in arith instructions,
+	 * because arguments type determine instruction used in result bytecode.
+	 * Example: (long) i << 32 - without 'long' cast will be used 'int shift' instruction and result
+	 * will be incorrect
+	 */
+	private static boolean isArithWideUpCast(@Nullable InsnNode parentInsn, ArgType argType, ArgType castToType) {
+		if (parentInsn != null
+				&& parentInsn.getType() == InsnType.ARITH
+				&& argType.isPrimitive() && castToType.isPrimitive()) {
+			return castToType.getRegCount() > argType.getRegCount();
+		}
+		return false;
+	}
+
 	private static boolean isCastDuplicate(IndexInsnNode castInsn) {
 		InsnArg arg = castInsn.getArg(0);
 		if (arg.isRegister()) {

jadx-core/src/test/java/jadx/tests/integration/types/TestLongCast.java

@@ -0,0 +1,37 @@
+package jadx.tests.integration.types;
+
+import org.junit.jupiter.api.Test;
+
+import jadx.tests.api.IntegrationTest;
+
+import static jadx.tests.api.utils.assertj.JadxAssertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class TestLongCast extends IntegrationTest {
+
+	public static class TestCls {
+
+		public long test(char c) {
+			return (long) c << 32;
+		}
+
+		public int test2(long l) {
+			return (int) l >> 2;
+		}
+
+		public void check() {
+			assertThat(test((char) 22)).isEqualTo(94489280512L);
+			assertThat(test2((1L << 32) + 8)).isEqualTo(2);
+		}
+	}
+
+	@Test
+	public void test() {
+		noDebugInfo();
+		assertThat(getClassNode(TestCls.class))
+				.code()
+				.containsOneOf(
+						"return (long) c << 32;",
+						"return ((long) c) << 32;");
+	}
+}