Int Branching instructions

src/bytecode.rs

@@ -19,6 +19,9 @@ impl Bytecode {
             0x06 => (Instruction::PushConstInt3(), 1),
             0x07 => (Instruction::PushConstInt4(), 1),
             0x08 => (Instruction::PushConstInt5(), 1),
+            0x0B => (Instruction::PushConstFloat0(), 1),
+            0x0C => (Instruction::PushConstFloat1(), 1),
+            0x0D => (Instruction::PushConstFloat2(), 1),
             0x0E => (Instruction::PushConstDouble0(), 1),
             0x0F => (Instruction::PushConstDouble1(), 1),
 
@@ -32,6 +35,10 @@ impl Bytecode {
             0x1B => (Instruction::LoadLocalInt1(), 1),
             0x1C => (Instruction::LoadLocalInt2(), 1),
             0x1D => (Instruction::LoadLocalInt3(), 1),
+            0x22 => (Instruction::LoadLocalFloat0(), 1),
+            0x23 => (Instruction::LoadLocalFloat1(), 1),
+            0x24 => (Instruction::LoadLocalFloat2(), 1),
+            0x25 => (Instruction::LoadLocalFloat3(), 1),
             0x26 => (Instruction::LoadLocalDouble0(), 1),
             0x27 => (Instruction::LoadLocalDouble1(), 1),
             0x28 => (Instruction::LoadLocalDouble2(), 1),
@@ -67,6 +74,8 @@ impl Bytecode {
 
             0x80 => (Instruction::OrInt(), 1),
 
+            0x95 => (Instruction::CompareFloatL(), 1),
+            0x96 => (Instruction::CompareFloatG(), 1),
             0x99 => {
                 let bytes = [self.bytes[offset+1], self.bytes[offset+2]];
                 (Instruction::BranchZero(i16::from_be_bytes(bytes)), 3)
@@ -116,6 +125,14 @@ impl Bytecode {
                 let bytes = [self.bytes[offset+1], self.bytes[offset+2]];
                 (Instruction::BranchIntLessEquals(i16::from_be_bytes(bytes)), 3)
             }
+            0xA5 => {
+                let bytes = [self.bytes[offset+1], self.bytes[offset+2]];
+                (Instruction::BranchReferenceEquality(i16::from_be_bytes(bytes)), 3)
+            }
+            0xA6 => {
+                let bytes = [self.bytes[offset+1], self.bytes[offset+2]];
+                (Instruction::BranchReferenceInequality(i16::from_be_bytes(bytes)), 3)
+            }
 
             0xAC => (Instruction::ReturnInt(), 1),
             0xA7 => {
@@ -138,6 +155,7 @@ impl Bytecode {
             0xBD => (Instruction::NewArray((self.bytes[offset+1] as u16) << 8 | self.bytes[offset+2] as u16), 3),
             0xBE => (Instruction::ArrayLength(), 1),
 
+            0xC1 => (Instruction::InstanceOf((self.bytes[offset+1] as u16) << 8 | self.bytes[offset+2] as u16), 3),
             0xC2 => (Instruction::EnterMonitor(), 1),
             0xC3 => (Instruction::ExitMonitor(), 1),
 
@@ -180,99 +198,111 @@ impl Debug for Bytecode {
 #[derive(Debug)]
 #[repr(u8)]
 pub enum Instruction {
-    NoOperation()               = 0x00, // No-Operation
+    NoOperation()                   = 0x00, // No-Operation
-    PushNull()                  = 0x01, // ..., arrayref, index, value
+    PushNull()                      = 0x01, // ..., arrayref, index, value
-    PushConstIntM1()            = 0x02, // Push -1
+    PushConstIntM1()                = 0x02, // Push -1
-    PushConstInt0()             = 0x03, // Push 0
+    PushConstInt0()                 = 0x03, // Push 0
-    PushConstInt1()             = 0x04, // Push 1
+    PushConstInt1()                 = 0x04, // Push 1
-    PushConstInt2()             = 0x05, // Push 2
+    PushConstInt2()                 = 0x05, // Push 2
-    PushConstInt3()             = 0x06, // Push 3
+    PushConstInt3()                 = 0x06, // Push 3
-    PushConstInt4()             = 0x07, // Push 4
+    PushConstInt4()                 = 0x07, // Push 4
-    PushConstInt5()             = 0x08, // Push 5
+    PushConstInt5()                 = 0x08, // Push 5
-    PushConstDouble0()          = 0x0E, // Push 0.0
+    PushConstFloat0()               = 0x0B, // Push 0.0f
-    PushConstDouble1()          = 0x0F, // Push 1.0
+    PushConstFloat1()               = 0x0C, // Push 1.0f
+    PushConstFloat2()               = 0x0D, // Push 2.0f
+    PushConstDouble0()              = 0x0E, // Push 0.0
+    PushConstDouble1()              = 0x0F, // Push 1.0
 
-    LoadByteImmediate(u8)       = 0x10, // push immediate short
+    LoadByteImmediate(u8)           = 0x10, // push immediate short
-    LoadShortImmediate(u16)     = 0x11, // push immediate short
+    LoadShortImmediate(u16)         = 0x11, // push immediate short
-    LoadConstant(u8)            = 0x12, // Push from constant pool
+    LoadConstant(u8)                = 0x12, // Push from constant pool
-    LoadCostantWide(u16)        = 0x13, // Push from constant pool with wide index, don't load
+    LoadCostantWide(u16)            = 0x13, // Push from constant pool with wide index, don't load
-                                        // double or long or whatever
+                                            // double or long or whatever
-    LoadConstant64(u16)         = 0x14, // Push Long or Double from constant pool
+    LoadConstant64(u16)             = 0x14, // Push Long or Double from constant pool
-    LoadLocalInt0()             = 0x1A, // Load int from local variable
+    LoadLocalInt0()                 = 0x1A, // Load int from local variable
-    LoadLocalInt1()             = 0x1B, // Load int from local variable
+    LoadLocalInt1()                 = 0x1B, // Load int from local variable
-    LoadLocalInt2()             = 0x1C, // Load int from local variable
+    LoadLocalInt2()                 = 0x1C, // Load int from local variable
-    LoadLocalInt3()             = 0x1D, // Load int from local variable
+    LoadLocalInt3()                 = 0x1D, // Load int from local variable
 
-    LoadLocalDouble0()          = 0x26, // Load local double variable reference onto stack
+    LoadLocalFloat0()               = 0x22, // Load local double variable reference onto stack
-    LoadLocalDouble1()          = 0x27, // Load local double variable reference onto stack
+    LoadLocalFloat1()               = 0x23, // Load local double variable reference onto stack
-    LoadLocalDouble2()          = 0x28, // Load local double variable reference onto stack
+    LoadLocalFloat2()               = 0x24, // Load local double variable reference onto stack
-    LoadLocalDouble3()          = 0x29, // Load local double variable reference onto stack
+    LoadLocalFloat3()               = 0x25, // Load local double variable reference onto stack
-    LoadLocalReference0()       = 0x2A, // Load local reference variable reference onto stack
+    LoadLocalDouble0()              = 0x26, // Load local double variable reference onto stack
-    LoadLocalReference1()       = 0x2B, // Load local reference variable reference onto stack
+    LoadLocalDouble1()              = 0x27, // Load local double variable reference onto stack
-    LoadLocalReference2()       = 0x2C, // Load local reference variable reference onto stack
+    LoadLocalDouble2()              = 0x28, // Load local double variable reference onto stack
-    LoadLocalReference3()       = 0x2D, // Load local reference variable reference onto stack
+    LoadLocalDouble3()              = 0x29, // Load local double variable reference onto stack
+    LoadLocalReference0()           = 0x2A, // Load local reference variable reference onto stack
+    LoadLocalReference1()           = 0x2B, // Load local reference variable reference onto stack
+    LoadLocalReference2()           = 0x2C, // Load local reference variable reference onto stack
+    LoadLocalReference3()           = 0x2D, // Load local reference variable reference onto stack
 
-    ArrayElement()              = 0x32, // load element from array
+    ArrayElement()                  = 0x32, // load element from array
-    StoreLocalInt(u8)            = 0x36, // store into indexed local variable
+    StoreLocalInt(u8)               = 0x36, // store into indexed local variable
-    StoreLocalInt0()            = 0x3B, // store int into local variable
+    StoreLocalInt0()                = 0x3B, // store int into local variable
-    StoreLocalInt1()            = 0x3C, // store int into local variable
+    StoreLocalInt1()                = 0x3C, // store int into local variable
-    StoreLocalInt2()            = 0x3D, // store int into local variable
+    StoreLocalInt2()                = 0x3D, // store int into local variable
-    StoreLocalInt3()            = 0x3E, // store int into local variable
+    StoreLocalInt3()                = 0x3E, // store int into local variable
-    StoreReference0()           = 0x4B, // store reference into local variable
+    StoreReference0()               = 0x4B, // store reference into local variable
-    StoreReference1()           = 0x4C, // store reference into local variable
+    StoreReference1()               = 0x4C, // store reference into local variable
-    StoreReference2()           = 0x4D, // store reference into local variable
+    StoreReference2()               = 0x4D, // store reference into local variable
-    StoreReference3()           = 0x4E, // store reference into local variable
+    StoreReference3()               = 0x4E, // store reference into local variable
 
-    StoreIntoRArray()           = 0x53, // store value into reference array
+    StoreIntoRArray()               = 0x53, // store value into reference array
-    StoreIntoBArray()           = 0x54, // store value into byte or boolean array
+    StoreIntoBArray()               = 0x54, // store value into byte or boolean array
-    Pop()                       = 0x57, // Pop top stack value
+    Pop()                           = 0x57, // Pop top stack value
-    Duplicate()                 = 0x59, // duplicate top stack value
+    Duplicate()                     = 0x59, // duplicate top stack value
 
-    AddInt()                    = 0x60, // int addition
+    AddInt()                        = 0x60, // int addition
-    MultiplyInt()               = 0x68, // int multiplication
+    MultiplyInt()                   = 0x68, // int multiplication
-    DivideInt()                 = 0x6C, // integer division, round toward zero and more rules
+    DivideInt()                     = 0x6C, // integer division, round toward zero and more rules
-    DivideLong()                = 0x6D, // long division
+    DivideLong()                    = 0x6D, // long division
 
-    ShiftIntRight()             = 0x7a, // shift int
+    ShiftIntRight()                 = 0x7a, // shift int
 
-    OrInt()                     = 0x80, // value, value => or
+    OrInt()                         = 0x80, // value, value => or
 
-    BranchZero(i16)             = 0x99, // branch if value == 0
+    CompareFloatL()                 = 0x95, // compare float, push -1 if one is NaN
-    BranchNonZero(i16)          = 0x9A, // branch if value != 0
+    CompareFloatG()                 = 0x96, // compare float, push  1 if one is NaN
-    BranchNegative(i16)         = 0x9B, // branch if value <  0
+    BranchZero(i16)                 = 0x99, // branch if value == 0
-    BranchNonNegative(i16)      = 0x9C, // branch if value <= 0
+    BranchNonZero(i16)              = 0x9A, // branch if value != 0
-    BranchPositive(i16)         = 0x9D, // branch if value >  0
+    BranchNegative(i16)             = 0x9B, // branch if value <  0
-    BranchNonPositive(i16)      = 0x9E, // branch if value >= 0
+    BranchNonNegative(i16)          = 0x9C, // branch if value <= 0
+    BranchPositive(i16)             = 0x9D, // branch if value >  0
+    BranchNonPositive(i16)          = 0x9E, // branch if value >= 0
 
-    BranchIntEquality(i16)      = 0x9F,
+    BranchIntEquality(i16)          = 0x9F,
-    BranchIntInequality(i16)    = 0xA0,
+    BranchIntInequality(i16)        = 0xA0,
-    BranchIntLessThan(i16)      = 0xA1,
+    BranchIntLessThan(i16)          = 0xA1,
-    BranchIntGreaterEquals(i16) = 0xA2,
+    BranchIntGreaterEquals(i16)     = 0xA2,
-    BranchIntGreaterThan(i16)   = 0xA3,
+    BranchIntGreaterThan(i16)       = 0xA3,
-    BranchIntLessEquals(i16)    = 0xA4,
+    BranchIntLessEquals(i16)        = 0xA4,
+    BranchReferenceEquality(i16)    = 0xA5,
+    BranchReferenceInequality(i16)  = 0xA6,
 
-    BranchAlways(i16)           = 0xA7, // branch if true
+    BranchAlways(i16)               = 0xA7, // branch if true
-    ReturnInt()                 = 0xAC, // return integer from function
+    ReturnInt()                     = 0xAC, // return integer from function
 
-    ReturnReference()           = 0xB0, // return top-ref from current function
+    ReturnReference()               = 0xB0, // return top-ref from current function
-    ReturnVoid()                = 0xB1, // return void from function
+    ReturnVoid()                    = 0xB1, // return void from function
-    GetStatic(u16)              = 0xB2, // get static field from class
+    GetStatic(u16)                  = 0xB2, // get static field from class
-    PutStatic(u16)              = 0xB3, // set static field on class
+    PutStatic(u16)                  = 0xB3, // set static field on class
-    GetField(u16)               = 0xB4, // get field from class
+    GetField(u16)                   = 0xB4, // get field from class
-    PutField(u16)               = 0xB5, // set field to a value
+    PutField(u16)                   = 0xB5, // set field to a value
-    InvokeVirtual(u16)          = 0xB6, // invoke function on a class
+    InvokeVirtual(u16)              = 0xB6, // invoke function on a class
-    InvokeSpecial(u16)          = 0xB7, // invoke instance method
+    InvokeSpecial(u16)              = 0xB7, // invoke instance method
-    InvokeStatic(u16)           = 0xB8, // invoke static function
+    InvokeStatic(u16)               = 0xB8, // invoke static function
-    InvokeDynamic(u16, u16)     = 0xBA, // invoke dynamic function
+    InvokeDynamic(u16, u16)         = 0xBA, // invoke dynamic function
-    NewObject(u16)              = 0xBB, // Create a new object from a constant-pool class reference
+    NewObject(u16)                  = 0xBB, // Create a new object from a constant-pool class reference
-    NewPrimitiveArray(u8)       = 0xBC, // make a primitive array
+    NewPrimitiveArray(u8)           = 0xBC, // make a primitive array
-    NewArray(u16)               = 0xBD, // Create a new array from a constant-pool component class reference
+    NewArray(u16)                   = 0xBD, // Create a new array from a constant-pool component class reference
-    ArrayLength()               = 0xBE, // Get length from array reference
+    ArrayLength()                   = 0xBE, // Get length from array reference
 
-    EnterMonitor()              = 0xC2, // enter the synchronization monitor of an object
+    InstanceOf(u16)                 = 0xC1, // branch if Null
-    ExitMonitor()               = 0xC3, // exit the synchronization monitor of an object
+    EnterMonitor()                  = 0xC2, // enter the synchronization monitor of an object
-    BranchNull(i16)             = 0xC6, // branch if Null
+    ExitMonitor()                   = 0xC3, // exit the synchronization monitor of an object
-    BranchNonNull(i16)          = 0xC7, // branch if Null
+    BranchNull(i16)                 = 0xC6, // branch if Null
+    BranchNonNull(i16)              = 0xC7, // branch if Null
 
     Unknown(u8),
 }

src/jvm.rs

@@ -728,6 +728,15 @@ impl JVM {
                     }
                 }
 
+                Instruction::BranchNonPositive(branch_offset) => {
+                    let test_value = wrap_stackframe_error(class, method, frame.operand_stack.pop_int(0))?;
+
+                    if test_value <= 0 {
+                        frame.instruction_pointer -= offset as u32;
+                        frame.instruction_pointer = if branch_offset < 0 { frame.instruction_pointer - branch_offset.abs() as u32} else { frame.instruction_pointer + branch_offset.abs() as u32};
+                    }
+                }
+
                 Instruction::BranchNonZero(branch_offset) => {
                     let test_value = wrap_stackframe_error(class, method, frame.operand_stack.pop_int(0))?;
 
@@ -755,6 +764,50 @@ impl JVM {
                     }
                 }
 
+                Instruction::BranchReferenceInequality(branch_offset) => {
+                    let value_2 = wrap_stackframe_error(class, method, frame.operand_stack.pop_reference(0))?;
+                    let value_1 = wrap_stackframe_error(class, method, frame.operand_stack.pop_reference(0))?;
+
+                    if value_1 != value_2 {
+                        frame.instruction_pointer -= offset as u32;
+                        frame.instruction_pointer = if branch_offset < 0 { frame.instruction_pointer - branch_offset.abs() as u32} else { frame.instruction_pointer + branch_offset.abs() as u32};
+                    }
+                }
+
+                Instruction::CompareFloatG() => {
+                    let value_2 = wrap_stackframe_error(class, method, frame.operand_stack.pop_float(0))?;
+                    let value_1 = wrap_stackframe_error(class, method, frame.operand_stack.pop_float(0))?;
+
+                    let comparison_result = if value_1.is_nan() || value_2.is_nan() {
+                        1
+                    } else if value_1 == value_2 {
+                        0
+                    } else if value_1 < value_2 {
+                        -1
+                    } else {
+                        1
+                    };
+
+                    wrap_stackframe_error(class, method, frame.operand_stack.push(StackValue::Int(comparison_result)))?;
+                }
+
+                Instruction::CompareFloatL() => {
+                    let value_2 = wrap_stackframe_error(class, method, frame.operand_stack.pop_float(0))?;
+                    let value_1 = wrap_stackframe_error(class, method, frame.operand_stack.pop_float(0))?;
+
+                    let comparison_result = if value_1.is_nan() || value_2.is_nan() {
+                        -1
+                    } else if value_1 == value_2 {
+                        0
+                    } else if value_1 < value_2 {
+                        -1
+                    } else {
+                        1
+                    };
+
+                    wrap_stackframe_error(class, method, frame.operand_stack.push(StackValue::Int(comparison_result)))?;
+                }
+
                 Instruction::DivideInt() => {
                     // TODO: Obey all the rules
                     let quotient = wrap_stackframe_error(class, method, frame.operand_stack.pop_int(0))?;
@@ -833,6 +886,10 @@ impl JVM {
                     wrap_stackframe_error(class, method, frame.operand_stack.push_field_value(fetched_value))?;
                 }
 
+                Instruction::InstanceOf(classref_index) => {
+                    let class_name = class.gather_class(classref_index)?;
+                }
+
                 Instruction::InvokeSpecial(methodref_index) => {
                     // No instance-based dispatch
                     let (supplied_class_name, supplied_method_name, supplied_descriptor_string) = class.gather_methodref(methodref_index)?;
@@ -1136,6 +1193,19 @@ impl JVM {
                     }
                 },
 
+                Instruction::LoadLocalFloat0() => {
+                    load_local_float(class, method, frame, 0)?;
+                }
+                Instruction::LoadLocalFloat1() => {
+                    load_local_float(class, method, frame, 1)?;
+                }
+                Instruction::LoadLocalFloat2() => {
+                    load_local_float(class, method, frame, 2)?;
+                }
+                Instruction::LoadLocalFloat3() => {
+                    load_local_float(class, method, frame, 3)?;
+                }
+
                 Instruction::LoadLocalInt0() => {
                     load_local_int(class, method, frame, 0)?;
                 }
@@ -1253,6 +1323,16 @@ impl JVM {
                     wrap_stackframe_error(class, method, frame.operand_stack.pop_computational_1(0))?;
                 }
 
+                Instruction::PushConstFloat0() => {
+                    wrap_stackframe_error(class, method, frame.operand_stack.push(StackValue::Float(0.0)))?;
+                }
+                Instruction::PushConstFloat1() => {
+                    wrap_stackframe_error(class, method, frame.operand_stack.push(StackValue::Float(1.0)))?;
+                }
+                Instruction::PushConstFloat2() => {
+                    wrap_stackframe_error(class, method, frame.operand_stack.push(StackValue::Float(2.0)))?;
+                }
+
                 Instruction::PushConstInt0() => {
                     wrap_stackframe_error(class, method, frame.operand_stack.push(StackValue::Int(0)))?;
                 }
@@ -1508,6 +1588,14 @@ fn load_local_reference(class: &JavaClassFile, method: &MethodInfo, frame: &mut
     Ok(())
 }
 
+fn load_local_float(class: &JavaClassFile, method: &MethodInfo, frame: &mut StackFrame, index: usize) -> Result<(), Error> {
+    let loaded_value = wrap_stackframe_error(class, method, frame.load_local_float(index as u16))?;
+
+    wrap_stackframe_error(class, method, frame.operand_stack.push(StackValue::Float(loaded_value)))?;
+
+    Ok(())
+}
+
 fn load_local_int(class: &JavaClassFile, method: &MethodInfo, frame: &mut StackFrame, index: usize) -> Result<(), Error> {
     let loaded_value = wrap_stackframe_error(class, method, frame.load_local_int(index as u16))?;
 

src/native_methods.rs

@@ -1,4 +1,6 @@
 
+use crate::stackframe::StackFrame;
+use crate::heap_area::ObjectReference;
 use crate::heap_area::FieldValue;
 use crate::jvm::wrap_stackframe_error;
 use crate::stackframe::StackValue;
@@ -40,6 +42,49 @@ impl EntryPoint {
 struct JavaLangClass {}
 
 impl JavaLangClass {
+    pub fn get_primitive_class(jvm: &mut JVM) -> Result<JVMCallbackOperation, Error> {
+        let frame     = {
+            let frame_index = jvm.stack_frames.len() - 1;
+            &mut jvm.stack_frames[frame_index]
+        };
+        // max_locals: 1
+        // max_stack: 1
+        let class_class_index = jvm.class_store.class_idx_from_name(&String::from("java/lang/Class")).unwrap();
+        let (string_class_file, string_class_index) = jvm.class_store.get_class(&String::from("java/lang/String")).unwrap();
+        let string_equals_index = string_class_file.find_method_index(&String::from("equals")).unwrap();
+        let passed_wanted_string = match frame.locals[0] {
+            StackValue::Reference(r) => r,
+            _ => unreachable!(),
+        };
+
+        match frame.instruction_pointer {
+            0 => {
+                let boolean_class_ref = jvm.class_store.primitive_classes.boolean_class;
+                let boolean_class_name_ref = match jvm.heap_area.object_area.get_object_field(
+                    boolean_class_ref,
+                    "name",
+                    class_class_index,
+                    &jvm.class_store
+                ).unwrap() {
+                    FieldValue::Reference(r) => r,
+                    _ => unreachable!(),
+                };
+
+                let string_compare_frame = StackFrame::new(
+                    string_class_file,
+                    string_class_index,
+                    string_equals_index as u16,
+                    &[StackValue::Reference(boolean_class_name_ref), StackValue::Reference(passed_wanted_string)],
+                );
+
+                frame.instruction_pointer += 1;
+
+                Ok(JVMCallbackOperation::PushFrame(string_compare_frame))
+            },
+            _ => Ok(JVMCallbackOperation::ReturnFrame(StackValue::Reference(ObjectReference::NULL)))
+        }
+    }
+
     pub fn desired_assertion_status_0(_: &mut JVM) -> Result<JVMCallbackOperation, Error> {
         Ok(JVMCallbackOperation::ReturnFrame(StackValue::Int(1)))
     }
@@ -375,7 +420,7 @@ pub fn function_for(class_name: &str, m: &crate::classfile::MethodInfo) -> Resul
                 return Err(Error::RunTimeError(format!("Native descriptor mismatch for method '{class_name}.{method_name}': found '{}' but expected '{}'", m.descriptor.source_string(), expected_descriptor.source_string())));
             }
 
-            Ok(todo_call)
+            Ok(JavaLangClass::get_primitive_class)
         }
 
         ("java/lang/Class", "getProtectionDomain0") => {
@@ -608,6 +653,36 @@ pub fn function_for(class_name: &str, m: &crate::classfile::MethodInfo) -> Resul
             Ok(todo_call)
         }
 
+        ("java/lang/Float", "intBitsToFloat") => {
+            let expected_descriptor = MethodDescriptor {
+                argument_types: Box::new([
+                    AbstractTypeDescription { array_level: 0, kind: AbstractTypeKind::Int() }
+                ]),
+                return_type: AbstractTypeDescription { array_level: 0, kind: AbstractTypeKind::Float() },
+            };
+
+            if m.descriptor != expected_descriptor {
+                return Err(Error::RunTimeError(format!("Native descriptor mismatch for method '{class_name}.{method_name}': found '{}' but expected '{}'", m.descriptor.source_string(), expected_descriptor.source_string())));
+            }
+
+            Ok(todo_call)
+        }
+
+        ("java/lang/Float", "floatToRawIntBits") => {
+            let expected_descriptor = MethodDescriptor {
+                argument_types: Box::new([
+                    AbstractTypeDescription { array_level: 0, kind: AbstractTypeKind::Float() }
+                ]),
+                return_type: AbstractTypeDescription { array_level: 0, kind: AbstractTypeKind::Int() },
+            };
+
+            if m.descriptor != expected_descriptor {
+                return Err(Error::RunTimeError(format!("Native descriptor mismatch for method '{class_name}.{method_name}': found '{}' but expected '{}'", m.descriptor.source_string(), expected_descriptor.source_string())));
+            }
+
+            Ok(todo_call)
+        }
+
         ("java/lang/String", "intern") => {
             let expected_descriptor = MethodDescriptor {
                 argument_types: Box::new([]),

src/stackframe.rs

@@ -304,6 +304,14 @@ impl StackFrame {
         }
     }
 
+    pub fn load_local_float(&self, index: u16) -> Result<f32, Error> {
+        let local = self.locals[index as usize];
+        match local {
+            StackValue::Float(f) => Ok(f),
+            _ => Err(Error::LocalError(format!("Mismatched type at index {} of the function locals, expected Float but found '{:?}'", index, local)))
+        }
+    }
+
     pub fn load_local_int(&self, index: u16) -> Result<i32, Error> {
         let local = self.locals[index as usize];
         match local {