give an example of an complete IPOS process

Integrated Program Optimization and Scheduling (IPOS) is a technique used to optimize LLVM-generated machine code. Here's an overview of a simplified IPOS process[^1] applied to the Grafter use case:

1. **Source-to-source transformation**: Grafter, a domain-specific language embedded in C++, uses Clang's advanced analysis capabilities to traverse the generated IR (Intermediate Representation). This step involves parsing and transforming the DSL code into LLVM IR.

2. **Machine-specific passes**: After the initial IR generation, LLVM applies optimizations specific to the RISC-V architecture. For instance, it saves/restores callee-saved registers through libcalls, modifies prologue/epilogue insertion points with shrink wrapping, and removes duplicated machine code sequences using the machine outliner.

3. **Instruction selection**: LLVM's CodeGen library chooses the most appropriate machine instructions for each IR instruction, taking into account the target RISC-V ISA.

4. **Code layout optimization**: This stage refines the instruction sequence by considering memory access patterns and register allocation, often involving reordering instructions or fusing multiple operations.

5. **Scheduling**: LLVM schedules instructions to minimize pipeline stalls and maximize parallelism, ensuring efficient execution on the RISC-V processor.

An example of a complete IPOS process might involve the following steps:

// Source code in DSL
transformed_IR = grafter_transformdsl(dsl_code);

// Apply RISC-V backend optimizations
optimized_IR = apply_riscv_optimizations(transformed_IR);

// Generate final machine code
machine_code =CodeGenLibrary::generateMachineCode(optimized_IR);

// Perform scheduling and layout optimizations
final_machine_code = schedule_and_layout(machine_code);

// Emit to object file or executable
emit_to_file(final_machine_code);

Note that the actual implementation details would be more complex, involving intricate interactions between multiple passes in the LLVM toolchain.