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-rw-r--r--examples/bf.rs47
1 files changed, 25 insertions, 22 deletions
diff --git a/examples/bf.rs b/examples/bf.rs
index ce2a682..f288178 100644
--- a/examples/bf.rs
+++ b/examples/bf.rs
@@ -21,6 +21,8 @@ use juicebox_asm::insn::*;
use juicebox_asm::Runtime;
use juicebox_asm::{Asm, Imm64, Imm8, Label, MemOp, MemOp8, Reg64, Reg8};
+// -- BRAINFUCK INTERPRETER ----------------------------------------------------
+
struct BrainfuckInterp {
pc: usize,
imem: Vec<char>,
@@ -31,8 +33,9 @@ struct BrainfuckInterp {
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.
+ // 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.
let (imem, branches) = {
// Instruction memory holding the final bf program.
let mut imem = Vec::new();
@@ -130,7 +133,7 @@ fn run_interp(prog: &str) {
}
}
-// -- BRAINFUCK JIT --------------------------------------------------------------
+// -- BRAINFUCK JIT ------------------------------------------------------------
#[cfg(not(any(target_arch = "x86_64", target_os = "linux")))]
compile_error!("Only supported on x86_64 with SystemV abi");
@@ -142,7 +145,8 @@ struct BrainfuckJit {
impl BrainfuckJit {
fn new(prog: &str) -> Result<Self, String> {
- // Do a first pass over the bf program to filter whitespace and detect invalid tokens.
+ // Do a first pass over the bf program to filter whitespace and detect
+ // invalid tokens.
let imem = prog
.chars()
.filter(|c| !c.is_whitespace())
@@ -168,20 +172,19 @@ extern "C" fn putchar(c: u8) {
fn run_jit(prog: &str) {
let mut vm = BrainfuckJit::new(prog).unwrap();
- // Use callee saved registers to hold vm state, such that we don't
- // need to save any state before calling out to putchar.
+ // Use callee saved registers to hold vm state, such that we don't need to
+ // save any state before calling out to putchar.
let dmem_base = Reg64::rbx;
let dmem_idx = Reg64::r12;
let mut asm = Asm::new();
- // Move data memory pointer (argument on jit entry) into correct
- // register.
+ // Move data memory pointer (argument on jit entry) into correct register.
asm.mov(dmem_base, Reg64::rdi);
// Clear data memory index.
asm.xor(dmem_idx, dmem_idx);
- // A stack of label pairs, used to link up forward and backward
- // jumps for a given '[]' pair.
+ // A stack of label pairs, used to link up forward and backward jumps for a
+ // given '[]' pair.
let mut label_stack = Vec::new();
// Generate code for each instruction in the bf program.
@@ -202,12 +205,11 @@ fn run_jit(prog: &str) {
asm.dec(MemOp8::from(MemOp::IndirectBaseIndex(dmem_base, dmem_idx)));
}
'.' => {
- // Load data memory from active cell into di register,
- // which is the first argument register according to
- // the SystemV abi, then call into putchar. Since we
- // stored all out vm state in callee saved registers
- // we don't need to save any registers before the
- // call.
+ // Load data memory from active cell into di register, which is
+ // the first argument register according to the SystemV abi,
+ // then call into putchar. Since we stored all out vm state in
+ // callee saved registers we don't need to save any registers
+ // before the call.
asm.mov(Reg8::dil, MemOp::IndirectBaseIndex(dmem_base, dmem_idx));
asm.mov(Reg64::rax, Imm64::from(putchar as usize));
asm.call(Reg64::rax);
@@ -229,8 +231,8 @@ fn run_jit(prog: &str) {
);
asm.jz(&mut label_pair.0);
- // Bind label_pair.1 after the jump instruction, which
- // will be the branch target for the matching ']'.
+ // Bind label_pair.1 after the jump instruction, which will be
+ // the branch target for the matching ']'.
asm.bind(&mut label_pair.1);
}
']' => {
@@ -238,8 +240,7 @@ fn run_jit(prog: &str) {
.pop()
.expect("encountered un-balanced brackets, found ']' without matching '['");
- // Goto label_pair.1 if data memory at active cell is
- // not 0.
+ // Goto label_pair.1 if data memory at active cell is not 0.
// if vm.dmem[vm.dptr] != 0 goto label_pair.1
asm.cmp(
MemOp::IndirectBaseIndex(dmem_base, dmem_idx),
@@ -247,8 +248,8 @@ fn run_jit(prog: &str) {
);
asm.jnz(&mut label_pair.1);
- // Bind label_pair.0 after the jump instruction, which
- // is the branch target for the matching '['.
+ // Bind label_pair.0 after the jump instruction, which is the
+ // branch target for the matching '['.
asm.bind(&mut label_pair.0);
}
_ => unreachable!(),
@@ -268,6 +269,8 @@ fn run_jit(prog: &str) {
bf_entry(&mut vm.dmem as *mut u8);
}
+// -- MAIN ---------------------------------------------------------------------
+
fn main() {
// https://en.wikipedia.org/wiki/Brainfuck#Adding_two_values
//let inp = "++>+++++ [<+>-] ++++++++[<++++++>-]<.";