ristretto_jit 0.31.0

JVM JIT Compiler
Documentation 
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use crate::Error::{InvalidConstant, InvalidConstantIndex, UnsupportedType};
use crate::Result;
use crate::operand_stack::OperandStack;
use cranelift::prelude::{FunctionBuilder, InstBuilder, types};
use ristretto_classfile::{Constant, ConstantPool};

/// # References
/// - [JVMS §6.5.ldc](https://docs.oracle.com/javase/specs/jvms/se25/html/jvms-6.html#jvms-6.5.ldc)
pub(crate) fn ldc(
    constant_pool: &ConstantPool,
    function_builder: &mut FunctionBuilder,
    stack: &mut OperandStack,
    index: u8,
) -> Result<()> {
    let index = u16::from(index);
    load_constant(constant_pool, function_builder, stack, index)
}

/// # References
/// - [JVMS §6.5.ldc_w](https://docs.oracle.com/javase/specs/jvms/se25/html/jvms-6.html#jvms-6.5.ldc_w)
pub(crate) fn ldc_w(
    constant_pool: &ConstantPool,
    function_builder: &mut FunctionBuilder,
    stack: &mut OperandStack,
    index: u16,
) -> Result<()> {
    load_constant(constant_pool, function_builder, stack, index)
}

/// Load the constant at the specified index onto the stack
///
/// # Errors
///
/// if the constant is not an integer, float, string or class
fn load_constant(
    constant_pool: &ConstantPool,
    function_builder: &mut FunctionBuilder,
    stack: &mut OperandStack,
    index: u16,
) -> Result<()> {
    let constant = constant_pool
        .get(index)
        .ok_or_else(|| InvalidConstantIndex(index))?;

    match constant {
        Constant::Integer(value) => {
            let value = i64::from(*value);
            let value = function_builder.ins().iconst(types::I32, value);
            stack.push_int(function_builder, value)?;
        }
        Constant::Float(value) => {
            let value = function_builder.ins().f32const(*value);
            stack.push_float(function_builder, value)?;
        }
        Constant::String(utf8_index) => {
            let _utf8_value = constant_pool.try_get_utf8(*utf8_index)?;
            return Err(UnsupportedType(
                "loading string constants not supported".to_string(),
            ));
        }
        Constant::Class(class_index) => {
            let _class_name = constant_pool.try_get_utf8(*class_index)?;
            return Err(UnsupportedType(
                "loading class constants not supported".to_string(),
            ));
        }
        constant => {
            return Err(InvalidConstant {
                expected: "integer|float|string|class".to_string(),
                actual: format!("{constant:?}"),
            });
        }
    }
    Ok(())
}

/// # References
/// - [JVMS §6.5.ldc2_w](https://docs.oracle.com/javase/specs/jvms/se25/html/jvms-6.html#jvms-6.5.ldc2_w)
pub(crate) fn ldc2_w(
    constant_pool: &ConstantPool,
    function_builder: &mut FunctionBuilder,
    stack: &mut OperandStack,
    index: u16,
) -> Result<()> {
    let constant = constant_pool
        .get(index)
        .ok_or_else(|| InvalidConstantIndex(index))?;

    match constant {
        Constant::Long(value) => {
            let value = function_builder.ins().iconst(types::I64, *value);
            stack.push(value)?;
        }
        Constant::Double(value) => {
            let value = function_builder.ins().f64const(*value);
            stack.push(value)?;
        }
        constant => {
            return Err(InvalidConstant {
                expected: "long|double".to_string(),
                actual: format!("{constant:?}"),
            });
        }
    }
    Ok(())
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::Compiler;
    use cranelift::frontend::FunctionBuilderContext;
    use cranelift::module::Module;

    #[test]
    fn test_load_constant_error() -> Result<()> {
        let compiler = Compiler::new()?;
        let jit_module = compiler.jit_module(&[]);
        let mut module_context = jit_module.make_context();
        let mut function_context = FunctionBuilderContext::new();
        let mut function_builder =
            FunctionBuilder::new(&mut module_context.func, &mut function_context);

        let mut constant_pool = ConstantPool::new();
        let index = constant_pool.add_long(42)?;
        let mut stack = OperandStack::with_capacity(1);

        let result = load_constant(&constant_pool, &mut function_builder, &mut stack, index);
        assert!(result.is_err());
        Ok(())
    }

    #[test]
    fn test_ldc2_w_constant_error() -> Result<()> {
        let compiler = Compiler::new()?;
        let jit_module = compiler.jit_module(&[]);
        let mut module_context = jit_module.make_context();
        let mut function_context = FunctionBuilderContext::new();
        let mut function_builder =
            FunctionBuilder::new(&mut module_context.func, &mut function_context);

        let mut constant_pool = ConstantPool::new();
        let index = constant_pool.add_integer(42)?;
        let mut stack = OperandStack::with_capacity(1);

        let result = ldc2_w(&constant_pool, &mut function_builder, &mut stack, index);
        assert!(result.is_err());
        Ok(())
    }
}