[view-compiler] DexBuilder: Add check-cast instruction

Bug: 111895153
Test: atest

Change-Id: I767e56713fab6beaa6970e58c4fc4d3560cc1304

4 files changed, 67 insertions, 8 deletions

diff --git a/startop/view_compiler/dex_builder.cc b/startop/view_compiler/dex_builder.cc
index 94879d0bbcc4..a78f7d53d135 100644
--- a/startop/view_compiler/dex_builder.cc
+++ b/startop/view_compiler/dex_builder.cc
@@ -79,6 +79,9 @@ std::ostream& operator<<(std::ostream& out, const Instruction::Op& opcode) {
     case Instruction::Op::kNew:
       out << "kNew";
       return out;
+    case Instruction::Op::kCheckCast:
+      out << "kCheckCast";
+      return out;
   }
 }
 
@@ -329,6 +332,8 @@ void MethodBuilder::EncodeInstruction(const Instruction& instruction) {
       return EncodeBranch(art::Instruction::IF_NEZ, instruction);
     case Instruction::Op::kNew:
       return EncodeNew(instruction);
+    case Instruction::Op::kCheckCast:
+      return EncodeCast(instruction);
   }
 }
 
@@ -422,6 +427,18 @@ void MethodBuilder::EncodeNew(const Instruction& instruction) {
   Encode21c(::art::Instruction::NEW_INSTANCE, RegisterValue(*instruction.dest()), type.value());
 }
 
+void MethodBuilder::EncodeCast(const Instruction& instruction) {
+  DCHECK_EQ(Instruction::Op::kCheckCast, instruction.opcode());
+  DCHECK(instruction.dest().has_value());
+  DCHECK(instruction.dest()->is_variable());
+  DCHECK_EQ(1, instruction.args().size());
+
+  const Value& type = instruction.args()[0];
+  DCHECK_LT(RegisterValue(*instruction.dest()), 256);
+  DCHECK(type.is_type());
+  Encode21c(::art::Instruction::CHECK_CAST, RegisterValue(*instruction.dest()), type.value());
+}
+
 size_t MethodBuilder::RegisterValue(const Value& value) const {
   if (value.is_register()) {
     return value.value();
diff --git a/startop/view_compiler/dex_builder.h b/startop/view_compiler/dex_builder.h
index 45596acfdc44..06059c8c6e56 100644
--- a/startop/view_compiler/dex_builder.h
+++ b/startop/view_compiler/dex_builder.h
@@ -142,17 +142,18 @@ class Instruction {
   // The operation performed by this instruction. These are virtual instructions that do not
   // correspond exactly to DEX instructions.
   enum class Op {
-    kReturn,
-    kReturnObject,
-    kMove,
-    kInvokeVirtual,
-    kInvokeDirect,
-    kInvokeStatic,
-    kInvokeInterface,
     kBindLabel,
     kBranchEqz,
     kBranchNEqz,
-    kNew
+    kCheckCast,
+    kInvokeDirect,
+    kInvokeInterface,
+    kInvokeStatic,
+    kInvokeVirtual,
+    kMove,
+    kNew,
+    kReturn,
+    kReturnObject,
   };
 
   ////////////////////////
@@ -168,6 +169,13 @@ class Instruction {
   static inline Instruction OpWithArgs(Op opcode, std::optional<const Value> dest, T... args) {
     return Instruction{opcode, /*method_id=*/0, /*result_is_object=*/false, dest, args...};
   }
+
+  // A cast instruction. Basically, `(type)val`
+  static inline Instruction Cast(Value val, Value type) {
+    DCHECK(type.is_type());
+    return OpWithArgs(Op::kCheckCast, val, type);
+  }
+
   // For method calls.
   template <typename... T>
   static inline Instruction InvokeVirtual(size_t method_id, std::optional<const Value> dest,
@@ -302,6 +310,7 @@ class MethodBuilder {
   void EncodeInvoke(const Instruction& instruction, ::art::Instruction::Code opcode);
   void EncodeBranch(art::Instruction::Code op, const Instruction& instruction);
   void EncodeNew(const Instruction& instruction);
+  void EncodeCast(const Instruction& instruction);
 
   // Low-level instruction format encoding. See
   // https://source.android.com/devices/tech/dalvik/instruction-formats for documentation of
diff --git a/startop/view_compiler/dex_builder_test/src/android/startop/test/DexBuilderTest.java b/startop/view_compiler/dex_builder_test/src/android/startop/test/DexBuilderTest.java
index 1508ad9ee56b..42d4161ee81e 100644
--- a/startop/view_compiler/dex_builder_test/src/android/startop/test/DexBuilderTest.java
+++ b/startop/view_compiler/dex_builder_test/src/android/startop/test/DexBuilderTest.java
@@ -20,6 +20,7 @@ import com.google.common.io.ByteStreams;
 import dalvik.system.InMemoryDexClassLoader;
 import dalvik.system.PathClassLoader;
 import java.io.InputStream;
+import java.lang.reflect.InvocationTargetException;
 import java.lang.reflect.Method;
 import java.nio.ByteBuffer;
 import org.junit.Assert;
@@ -151,4 +152,23 @@ public class DexBuilderTest {
     Method method = clazz.getMethod("invokeVirtualReturnObject", String.class, int.class);
     Assert.assertEquals("bc", method.invoke(null, "abc", 1));
   }
+
+  @Test
+  public void castObjectToString() throws Exception {
+    ClassLoader loader = loadDexFile("simple.dex");
+    Class clazz = loader.loadClass("android.startop.test.testcases.SimpleTests");
+    Method method = clazz.getMethod("castObjectToString", Object.class);
+    Assert.assertEquals("abc", method.invoke(null, "abc"));
+    boolean castFailed = false;
+    try {
+      method.invoke(null, 5);
+    } catch (InvocationTargetException e) {
+      if (e.getCause() instanceof ClassCastException) {
+        castFailed = true;
+      } else {
+        throw e;
+      }
+    }
+    Assert.assertTrue(castFailed);
+  }
 }
diff --git a/startop/view_compiler/dex_testcase_generator.cc b/startop/view_compiler/dex_testcase_generator.cc
index 2781aa55d1df..f62ec5dde85e 100644
--- a/startop/view_compiler/dex_testcase_generator.cc
+++ b/startop/view_compiler/dex_testcase_generator.cc
@@ -269,6 +269,19 @@ void GenerateSimpleTestCases(const string& outdir) {
     method.Encode();
   }(invokeVirtualReturnObject);
 
+  // Make sure we can cast objects
+  // String castObjectToString(Object o) { return (String)o; }
+  MethodBuilder castObjectToString{cbuilder.CreateMethod(
+      "castObjectToString",
+      Prototype{string_type, TypeDescriptor::FromClassname("java.lang.Object")})};
+  [&](MethodBuilder& method) {
+    const ir::Type* type_def = dex_file.GetOrAddType(string_type.descriptor());
+    method.AddInstruction(
+        Instruction::Cast(Value::Parameter(0), Value::Type(type_def->orig_index)));
+    method.BuildReturn(Value::Parameter(0), /*is_object=*/true);
+    method.Encode();
+  }(castObjectToString);
+
   slicer::MemView image{dex_file.CreateImage()};
   std::ofstream out_file(outdir + "/simple.dex");
   out_file.write(image.ptr<const char>(), image.size());