torsh_jit/

codegen.rs

//! Code generation backend for JIT compilation

use crate::graph::{ComputationGraph, Node, NodeId, Operation};
use crate::{CompiledKernel, JitError, JitResult, KernelMetadata, TensorDesc};
use torsh_core::DeviceType;

/// Code generator for different backends
pub struct CodeGenerator {
    device: DeviceType,
}

impl CodeGenerator {
    /// Create a new code generator for the target device
    pub fn new(device: DeviceType) -> Self {
        Self { device }
    }

    /// Generate code for the computation graph
    pub fn generate(&self, graph: &ComputationGraph) -> JitResult<Vec<CompiledKernel>> {
        match self.device {
            DeviceType::Cpu => self.generate_cpu(graph),
            DeviceType::Cuda(_) => self.generate_cuda(graph),
            DeviceType::Metal(_) => self.generate_metal(graph),
            _ => Err(JitError::UnsupportedOp(format!(
                "Code generation not supported for {:?}",
                self.device
            ))),
        }
    }

    /// Generate CPU code
    ///
    /// With the `cranelift-backend` feature the graph is lowered to IR and compiled
    /// by [`crate::cranelift_backend::CraneliftCodeGen`], which emits real machine
    /// code and refuses when the compiler produces nothing. Without the feature the
    /// interpreter encoding is used instead.
    fn generate_cpu(&self, graph: &ComputationGraph) -> JitResult<Vec<CompiledKernel>> {
        #[cfg(feature = "cranelift-backend")]
        {
            let ir_module = crate::lowering::lower_graph_to_ir(graph, "cpu_kernel".to_string())?;
            let mut codegen = crate::cranelift_backend::CraneliftCodeGen::new()?;
            let kernels = codegen.generate(&ir_module)?;

            // A kernel without code is not a kernel: reject it rather than handing
            // the caller something that looks compiled but executes nothing.
            if let Some(empty) = kernels.iter().find(|kernel| kernel.code.is_empty()) {
                return Err(JitError::CodeGenError(format!(
                    "Cranelift returned kernel '{}' with no machine code",
                    empty.id
                )));
            }

            Ok(kernels)
        }

        // Fallback to interpreter mode
        #[cfg(not(feature = "cranelift-backend"))]
        {
            self.generate_interpreter(graph)
        }
    }

    /// Generate CUDA code
    ///
    /// Future implementation will support:
    /// - PTX code generation for NVIDIA GPUs
    /// - Kernel fusion for memory bandwidth optimization
    /// - Tensor core utilization for matrix operations
    /// - Automatic memory coalescing
    /// - Multi-stream execution support
    fn generate_cuda(&self, graph: &ComputationGraph) -> JitResult<Vec<CompiledKernel>> {
        let node_count = graph.nodes().count();
        let operation_types: Vec<_> = graph
            .nodes()
            .map(|(_, node)| format!("{:?}", node.op))
            .collect();

        Err(JitError::UnsupportedOp(format!(
            "CUDA code generation not yet implemented. \
             Graph contains {} nodes with operations: {}. \
             To enable CUDA support: \
             1. Install CUDA toolkit (>=11.0) \
             2. Enable 'cuda' feature flag \
             3. Set CUDA_PATH environment variable \
             \nFallback: Use CPU backend or interpreter mode.",
            node_count,
            operation_types.join(", ")
        )))
    }

    /// Generate Metal code
    ///
    /// Future implementation will support:
    /// - Metal Shading Language (MSL) generation
    /// - Metal Performance Shaders (MPS) integration
    /// - Unified memory architecture optimization
    /// - Apple Neural Engine (ANE) acceleration
    /// - Multi-GPU support for Mac Pro
    fn generate_metal(&self, graph: &ComputationGraph) -> JitResult<Vec<CompiledKernel>> {
        let node_count = graph.nodes().count();
        let has_matmul = graph
            .nodes()
            .any(|(_, node)| matches!(node.op, Operation::MatMul));
        let has_conv = graph
            .nodes()
            .any(|(_, node)| matches!(node.op, Operation::Conv2d { .. }));

        let recommendations = if has_matmul || has_conv {
            "Consider using Metal Performance Shaders (MPS) backend for matrix/convolution operations."
        } else {
            "For element-wise operations, CPU backend may provide sufficient performance."
        };

        Err(JitError::UnsupportedOp(format!(
            "Metal code generation not yet implemented. \
             Graph contains {} nodes. \
             Detected: {} \
             To enable Metal support: \
             1. Ensure macOS 10.15+ or iOS 13+ \
             2. Enable 'metal' feature flag \
             3. Install Metal developer tools \
             \n{} \
             \nFallback: Use CPU backend or interpreter mode.",
            node_count,
            if has_matmul {
                "matrix multiplication"
            } else if has_conv {
                "convolutions"
            } else {
                "element-wise ops"
            },
            recommendations
        )))
    }

    /// Generate code from IR module  
    pub fn generate_from_ir(
        &self,
        ir_module: &crate::ir::IrModule,
    ) -> JitResult<Vec<CompiledKernel>> {
        // For now, convert IR back to graph-like representation and use existing logic
        // In a real implementation, this would generate code directly from IR
        self.generate_interpreter_from_ir(ir_module)
    }

    /// Generate interpreter kernels from IR
    pub fn generate_interpreter_from_ir(
        &self,
        ir_module: &crate::ir::IrModule,
    ) -> JitResult<Vec<CompiledKernel>> {
        let mut kernels = Vec::new();

        // For each basic block, create a kernel
        for (block_id, block) in &ir_module.blocks {
            let kernel_id = format!("ir_kernel_{}", block_id);

            // Create simple metadata
            let metadata = KernelMetadata {
                inputs: ir_module
                    .inputs
                    .iter()
                    .filter_map(|&input| self.ir_value_to_tensor_desc(ir_module, input))
                    .collect(),
                outputs: ir_module
                    .outputs
                    .iter()
                    .filter_map(|&output| self.ir_value_to_tensor_desc(ir_module, output))
                    .collect(),
                shared_memory: 0,
                block_size: (1, 1, 1),
                grid_size: (1, 1, 1),
            };

            // Encode the instructions
            let mut code = Vec::new();
            for instruction in &block.instructions {
                let opcode = self.encode_ir_instruction(instruction)?;
                code.push(opcode);
            }

            let kernel = CompiledKernel {
                id: kernel_id,
                source_nodes: Vec::new(), // Would need mapping from IR to original nodes
                code,
                metadata,
            };

            kernels.push(kernel);
        }

        Ok(kernels)
    }

    /// Convert IR value to tensor descriptor
    fn ir_value_to_tensor_desc(
        &self,
        ir_module: &crate::ir::IrModule,
        ir_value: crate::ir::IrValue,
    ) -> Option<TensorDesc> {
        if let Some(value_def) = ir_module.get_value(ir_value) {
            if let Some(type_def) = ir_module.get_type(value_def.ty) {
                match &type_def.kind {
                    crate::ir::TypeKind::Tensor { shape, .. } => {
                        Some(TensorDesc {
                            dtype: torsh_core::DType::F32, // Simplified
                            shape: shape.clone(),
                            strides: self.compute_strides(shape),
                            offset: 0,
                        })
                    }
                    _ => None,
                }
            } else {
                None
            }
        } else {
            None
        }
    }

    /// Encode an IR instruction
    fn encode_ir_instruction(&self, instruction: &crate::ir::Instruction) -> JitResult<u8> {
        let opcode = match &instruction.opcode {
            crate::ir::IrOpcode::Add => 1,
            crate::ir::IrOpcode::Sub => 2,
            crate::ir::IrOpcode::Mul => 3,
            crate::ir::IrOpcode::Div => 4,
            crate::ir::IrOpcode::Neg => 5,
            crate::ir::IrOpcode::Abs => 6,
            crate::ir::IrOpcode::Exp => 7,
            crate::ir::IrOpcode::Log => 8,
            crate::ir::IrOpcode::Sqrt => 9,
            crate::ir::IrOpcode::Sin => 10,
            crate::ir::IrOpcode::Cos => 11,
            crate::ir::IrOpcode::Tanh => 12,
            crate::ir::IrOpcode::Sigmoid => 13,
            crate::ir::IrOpcode::Relu => 14,
            crate::ir::IrOpcode::Gelu => 15,
            crate::ir::IrOpcode::MatMul => 16,
            crate::ir::IrOpcode::Conv2d => 17,
            crate::ir::IrOpcode::Pool2d => 18,
            crate::ir::IrOpcode::Reshape => 19,
            crate::ir::IrOpcode::Transpose => 20,
            crate::ir::IrOpcode::Sum => 21,
            crate::ir::IrOpcode::Mean => 22,
            crate::ir::IrOpcode::Max => 23,
            crate::ir::IrOpcode::Min => 24,
            crate::ir::IrOpcode::Load => 25,
            crate::ir::IrOpcode::Store => 26,
            crate::ir::IrOpcode::Const => 27,
            _ => {
                return Err(JitError::UnsupportedOp(format!(
                    "IR opcode {:?} not supported in interpreter",
                    instruction.opcode
                )))
            }
        };

        Ok(opcode)
    }

    /// Generate interpreter-based kernels (fallback)
    pub fn generate_interpreter(&self, graph: &ComputationGraph) -> JitResult<Vec<CompiledKernel>> {
        let mut kernels = Vec::new();

        // Get topological order
        let order = graph
            .topological_sort()
            .map_err(|e| JitError::GraphError(format!("{:?}", e)))?;

        // Generate a kernel for each node (simple approach)
        for node_id in order {
            if let Some(node) = graph.node(node_id) {
                let kernel = self.generate_interpreter_kernel(graph, node_id, node)?;
                kernels.push(kernel);
            }
        }

        Ok(kernels)
    }

    /// Generate an interpreter kernel for a single node
    fn generate_interpreter_kernel(
        &self,
        graph: &ComputationGraph,
        node_id: NodeId,
        node: &Node,
    ) -> JitResult<CompiledKernel> {
        // Populate inputs from graph
        let input_tensors: Vec<TensorDesc> = graph
            .get_node_inputs(node_id)
            .iter()
            .filter_map(|&input_id| {
                graph.node(input_id).map(|input_node| TensorDesc {
                    dtype: input_node.dtype,
                    shape: input_node.output_shape.dims().to_vec(),
                    strides: self.compute_strides(input_node.output_shape.dims()),
                    offset: 0,
                })
            })
            .collect();

        // Generate metadata
        let metadata = KernelMetadata {
            inputs: input_tensors,
            outputs: vec![TensorDesc {
                dtype: node.dtype,
                shape: node.output_shape.dims().to_vec(),
                strides: self.compute_strides(node.output_shape.dims()),
                offset: 0,
            }],
            shared_memory: 0,
            block_size: (1, 1, 1),
            grid_size: (1, 1, 1),
        };

        // Encode operation as "code"
        let code = self.encode_operation(&node.op)?;

        Ok(CompiledKernel {
            id: format!("kernel_{:?}", node_id),
            source_nodes: vec![node_id],
            code,
            metadata,
        })
    }

    /// Compute strides for a shape
    fn compute_strides(&self, shape: &[usize]) -> Vec<usize> {
        let mut strides = vec![1; shape.len()];
        for i in (0..shape.len() - 1).rev() {
            strides[i] = strides[i + 1] * shape[i + 1];
        }
        strides
    }

    /// Encode an operation for interpreter execution
    fn encode_operation(&self, op: &Operation) -> JitResult<Vec<u8>> {
        // Simple encoding scheme for interpreter
        let op_code = match op {
            Operation::Add => 1,
            Operation::Sub => 2,
            Operation::Mul => 3,
            Operation::Div => 4,
            Operation::Relu => 5,
            Operation::Sigmoid => 6,
            Operation::Tanh => 7,
            Operation::MatMul => 8,
            // ... more operations
            _ => {
                return Err(JitError::UnsupportedOp(format!(
                    "Operation {:?} not supported in interpreter",
                    op
                )))
            }
        };

        Ok(vec![op_code])
    }
}

/// CUDA kernel generator
///
/// Generates PTX (Parallel Thread Execution) code for NVIDIA GPUs.
/// Supports compute capabilities from 5.0 (Maxwell) to 9.0 (Hopper).
pub struct CudaKernelGenerator {
    compute_capability: (u32, u32),
    /// Enable tensor core usage for matrix operations (compute capability >= 7.0)
    enable_tensor_cores: bool,
    /// Target PTX ISA version
    ptx_version: (u32, u32),
    /// Enable cooperative groups
    enable_cooperative_groups: bool,
}

impl CudaKernelGenerator {
    /// Create a new CUDA kernel generator
    ///
    /// # Arguments
    /// * `compute_capability` - GPU compute capability (e.g., (7, 5) for sm_75)
    pub fn new(compute_capability: (u32, u32)) -> Self {
        let enable_tensor_cores = compute_capability.0 >= 7;
        let enable_cooperative_groups = compute_capability.0 >= 6;

        Self {
            compute_capability,
            enable_tensor_cores,
            ptx_version: (7, 0), // Default to PTX 7.0
            enable_cooperative_groups,
        }
    }

    /// Enable or disable tensor core usage
    pub fn set_tensor_cores(&mut self, enable: bool) {
        self.enable_tensor_cores = enable && self.compute_capability.0 >= 7;
    }

    /// Generate PTX assembly code for the computation graph
    ///
    /// Future implementation will:
    /// - Analyze graph for optimal thread block configuration
    /// - Generate fused kernels for element-wise operation chains
    /// - Emit specialized tensor core instructions (WMMA) for matrix ops
    /// - Apply memory coalescing patterns
    /// - Generate multi-kernel launches for large graphs
    pub fn generate_ptx(&self, graph: &ComputationGraph) -> JitResult<String> {
        let node_count = graph.nodes().count();
        let matmul_count = graph
            .nodes()
            .filter(|(_, n)| matches!(n.op, Operation::MatMul))
            .count();
        let conv_count = graph
            .nodes()
            .filter(|(_, n)| matches!(n.op, Operation::Conv2d { .. }))
            .count();

        let capability_str = format!(
            "sm_{}{}",
            self.compute_capability.0, self.compute_capability.1
        );
        let features = if self.enable_tensor_cores {
            "tensor cores (WMMA), "
        } else {
            ""
        };

        Err(JitError::UnsupportedOp(format!(
            "PTX generation not yet implemented.\n\
             Target: {} (compute capability {}.{})\n\
             Graph statistics:\n\
             - Total nodes: {}\n\
             - MatMul operations: {} {}\n\
             - Conv2D operations: {} {}\n\
             Features: {}cooperative groups\n\
             \n\
             Future PTX generation will support:\n\
             - Automatic kernel fusion for {:.1}x speedup potential\n\
             - Memory coalescing optimization\n\
             - Shared memory tiling for matrix operations\n\
             - Warp-level primitives for reduction operations\n\
             \nFallback: Use CPU backend with BLAS/MKL for good performance.",
            capability_str,
            self.compute_capability.0,
            self.compute_capability.1,
            node_count,
            matmul_count,
            if self.enable_tensor_cores {
                "(tensor core eligible)"
            } else {
                ""
            },
            conv_count,
            if conv_count > 0 {
                "(cudnn eligible)"
            } else {
                ""
            },
            features,
            (matmul_count + conv_count).max(1) as f64 * 1.5 // Estimated fusion speedup
        )))
    }

    /// Estimate kernel launch configuration for a graph
    pub fn estimate_launch_config(&self, graph: &ComputationGraph) -> LaunchConfiguration {
        let total_ops: usize = graph
            .nodes()
            .map(|(_, node)| node.output_shape.dims().iter().product::<usize>())
            .sum();

        // Simple heuristic for block size
        let threads_per_block = if total_ops < 1024 {
            128
        } else if total_ops < 1024 * 1024 {
            256
        } else {
            512
        };

        let blocks = (total_ops + threads_per_block - 1) / threads_per_block;

        LaunchConfiguration {
            grid_dim: (blocks.min(65535), 1, 1),
            block_dim: (threads_per_block, 1, 1),
            shared_memory_bytes: 0, // Would be calculated based on kernel
            stream_id: 0,
        }
    }
}

/// CUDA kernel launch configuration
#[derive(Debug, Clone)]
pub struct LaunchConfiguration {
    /// Grid dimensions (number of blocks)
    pub grid_dim: (usize, usize, usize),
    /// Block dimensions (threads per block)
    pub block_dim: (usize, usize, usize),
    /// Shared memory per block in bytes
    pub shared_memory_bytes: usize,
    /// CUDA stream ID
    pub stream_id: i32,
}

/// Metal kernel generator
///
/// Generates Metal Shading Language (MSL) code for Apple GPUs.
/// Supports macOS 10.15+, iOS 13+, and Apple Silicon.
pub struct MetalKernelGenerator {
    device_family: String,
    /// Enable Metal Performance Shaders (MPS) integration
    enable_mps: bool,
    /// Metal language version
    metal_version: (u32, u32),
    /// Target Apple Neural Engine (ANE) when available
    enable_ane: bool,
}

impl MetalKernelGenerator {
    /// Create a new Metal kernel generator
    ///
    /// # Arguments
    /// * `device_family` - Metal GPU family (e.g., "apple7" for M1)
    pub fn new(device_family: String) -> Self {
        // Detect if ANE is available (A11+ or Apple Silicon)
        let enable_ane = device_family.starts_with("apple")
            && device_family[5..].parse::<u32>().unwrap_or(0) >= 7;

        Self {
            device_family,
            enable_mps: true,      // MPS available on all modern devices
            metal_version: (2, 4), // Metal 2.4 for macOS 12+
            enable_ane,
        }
    }

    /// Enable or disable Metal Performance Shaders integration
    pub fn set_mps(&mut self, enable: bool) {
        self.enable_mps = enable;
    }

    /// Generate Metal Shading Language code for the computation graph
    ///
    /// Future implementation will:
    /// - Generate optimized MSL kernels for each operation
    /// - Integrate with Metal Performance Shaders for standard ops
    /// - Utilize tile memory for data reuse
    /// - Emit SIMD-group operations for reduction
    /// - Generate ANE-compatible operations when possible
    pub fn generate_metal(&self, graph: &ComputationGraph) -> JitResult<String> {
        let node_count = graph.nodes().count();
        let matmul_count = graph
            .nodes()
            .filter(|(_, n)| matches!(n.op, Operation::MatMul))
            .count();
        let conv_count = graph
            .nodes()
            .filter(|(_, n)| matches!(n.op, Operation::Conv2d { .. }))
            .count();
        let elementwise_count = node_count - matmul_count - conv_count;

        let mps_eligible = matmul_count + conv_count;
        let ane_hints = if self.enable_ane && conv_count > 0 {
            format!(
                "\n- {} convolution ops are ANE-eligible for ultra-low power inference",
                conv_count
            )
        } else {
            String::new()
        };

        Err(JitError::UnsupportedOp(format!(
            "Metal shader generation not yet implemented.\n\
             Target: {} (Metal {}. {})\n\
             Graph statistics:\n\
             - Total nodes: {}\n\
             - Element-wise ops: {}\n\
             - MatMul operations: {}\n\
             - Conv2D operations: {}\n\
             - MPS-eligible ops: {}{}\n\
             \n\
             Future Metal generation will support:\n\
             - Metal Performance Shaders integration for {:.0}% of operations\n\
             - Unified memory optimization (zero-copy on Apple Silicon)\n\
             - Tile memory usage for {:.1}x bandwidth reduction\n\
             - SIMD-group operations for efficient reduction\n\
             - Concurrent kernel execution across multiple command buffers\n\
             \nFallback: Use CPU backend with Accelerate framework for good performance.",
            self.device_family,
            self.metal_version.0,
            self.metal_version.1,
            node_count,
            elementwise_count,
            matmul_count,
            conv_count,
            mps_eligible,
            ane_hints,
            (mps_eligible as f64 / node_count as f64) * 100.0,
            2.5 // Estimated bandwidth reduction from tile memory
        )))
    }

    /// Estimate threadgroup size for a graph
    pub fn estimate_threadgroup_size(&self, graph: &ComputationGraph) -> ThreadgroupSize {
        let total_ops: usize = graph
            .nodes()
            .map(|(_, node)| node.output_shape.dims().iter().product::<usize>())
            .sum();

        // Metal recommends threadgroup sizes in multiples of SIMD width (32)
        let threads_per_threadgroup = if total_ops < 1024 {
            128
        } else if total_ops < 1024 * 1024 {
            256
        } else {
            512
        };

        ThreadgroupSize {
            width: threads_per_threadgroup,
            height: 1,
            depth: 1,
        }
    }
}

/// Metal threadgroup size configuration
#[derive(Debug, Clone)]
pub struct ThreadgroupSize {
    pub width: usize,
    pub height: usize,
    pub depth: usize,
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_code_generator_creation() {
        let _gen = CodeGenerator::new(DeviceType::Cpu);
        // Basic creation test
        assert!(true);
    }

    #[test]
    fn test_stride_computation() {
        let gen = CodeGenerator::new(DeviceType::Cpu);

        let strides = gen.compute_strides(&[2, 3, 4]);
        assert_eq!(strides, vec![12, 4, 1]);

        let strides = gen.compute_strides(&[10]);
        assert_eq!(strides, vec![1]);
    }
}