diff options
Diffstat (limited to 'examples')
| -rw-r--r-- | examples/bf.rs | 35 |
1 files changed, 21 insertions, 14 deletions
diff --git a/examples/bf.rs b/examples/bf.rs index ec02228..69d1bc1 100644 --- a/examples/bf.rs +++ b/examples/bf.rs @@ -1,7 +1,6 @@ //! Brainfuck VM. //! -//! This example implements a simple -//! [brainfuck](https://en.wikipedia.org/wiki/Brainfuck) interpreter +//! This example implements a simple [brainfuck][bf] interpreter //! [`BrainfuckInterp`] and a jit compiler [`BrainfuckJit`]. //! //! Brainfuck is an esoteric programming languge existing of 8 commands. @@ -11,8 +10,16 @@ //! - `-` decrement data at current data pointer. //! - `.` output data at current data pointer. //! - `,` read input and store at current data pointer. -//! - `[` jump behind matching ']' if data at data pointer is zero. -//! - `]` jump behind matching '[' if data at data pointer is non-zero. +//! - `[` jump behind matching `]` if data at data pointer is zero. +//! - `]` jump behind matching `[` if data at data pointer is non-zero. +//! +//! The following is the `hello-world` program from [wikipedia][hw]. +//! ``` +//! ++++++++[>++++[>++>+++>+++>+<<<<-]>+>+>->>+[<]<-]>>.>---.+++++++..+++.>>.<-.<.+++.------.--------.>>+.>++. +//! ``` +//! +//! [bf]: https://en.wikipedia.org/wiki/Brainfuck +//! [hw]: https://en.wikipedia.org/wiki/Brainfuck#Hello_World! use std::collections::HashMap; use std::io::Write; @@ -35,7 +42,7 @@ impl BrainfuckInterp { fn new(prog: &str) -> Result<Self, String> { // Do a first pass over the bf program to filter whitespace and detect // invalid tokens. Additionally validate all conditional branches, and - // compute their branch target. + // compute their branch targets. let (imem, branches) = { // Instruction memory holding the final bf program. let mut imem = Vec::new(); @@ -187,8 +194,8 @@ fn run_jit(prog: &str) { // Move data memory pointer (argument on jit entry) into correct register. asm.mov(dmem_base, Reg64::rdi); - // Move data memory size into correct register. - asm.mov(dmem_size, Reg64::rsi); + // Move data memory size (compile time constant) into correct register. + asm.mov(dmem_size, Imm64::from(vm.dmem.len())); // Clear data memory index. asm.xor(dmem_idx, dmem_idx); @@ -316,11 +323,11 @@ fn run_jit(prog: &str) { pc += 1; } - let mut ret_epilogue = Label::new(); + let mut epilogue = Label::new(); // Successful return from bf program. asm.xor(Reg64::rax, Reg64::rax); - asm.bind(&mut ret_epilogue); + asm.bind(&mut epilogue); // Restore callee saved registers before returning from jit. asm.pop(dmem_idx); asm.pop(dmem_size); @@ -330,12 +337,12 @@ fn run_jit(prog: &str) { // Return because of data pointer overflow. asm.bind(&mut oob_ov); asm.mov(Reg64::rax, Imm64::from(1)); - asm.jmp(&mut ret_epilogue); + asm.jmp(&mut epilogue); // Return because of data pointer underflow. asm.bind(&mut oob_uv); asm.mov(Reg64::rax, Imm64::from(2)); - asm.jmp(&mut ret_epilogue); + asm.jmp(&mut epilogue); if !label_stack.is_empty() { panic!("encountered un-balanced brackets, left-over '[' after jitting bf program") @@ -343,11 +350,11 @@ fn run_jit(prog: &str) { // Get function pointer to jitted bf program. let mut rt = Runtime::new(); - let bf_entry = unsafe { rt.add_code::<extern "C" fn(*mut u8, usize) -> u64>(asm.into_code()) }; + let bf_entry = unsafe { rt.add_code::<extern "C" fn(*mut u8) -> u64>(asm.into_code()) }; // Execute jitted bf program. - match bf_entry(&mut vm.dmem as *mut u8, vm.dmem.len()) { - 0 => {} + match bf_entry(&mut vm.dmem as *mut u8) { + 0 => { /* success */ } 1 => panic!("oob: data pointer overflow"), 2 => panic!("oob: data pointer underflow"), _ => unreachable!(), |