diff options
| -rw-r--r-- | examples/bf.rs | 48 |
1 files changed, 44 insertions, 4 deletions
diff --git a/examples/bf.rs b/examples/bf.rs index f288178..5d0da0b 100644 --- a/examples/bf.rs +++ b/examples/bf.rs @@ -188,8 +188,9 @@ fn run_jit(prog: &str) { let mut label_stack = Vec::new(); // Generate code for each instruction in the bf program. - for insn in vm.imem { - match insn { + let mut pc = 0; + while pc < vm.imem.len() { + match vm.imem[pc] { '>' => { // TODO: generate runtime bounds check. asm.inc(dmem_idx); @@ -199,10 +200,46 @@ fn run_jit(prog: &str) { asm.dec(dmem_idx); } '+' => { - asm.inc(MemOp8::from(MemOp::IndirectBaseIndex(dmem_base, dmem_idx))); + // Apply optimization to fold consecutive '+' instructions to a + // single add instruction during compile time. + + match vm.imem[pc..].iter().take_while(|&&i| i.eq(&'+')).count() { + 1 => asm.inc(MemOp8::from(MemOp::IndirectBaseIndex(dmem_base, dmem_idx))), + cnt if cnt <= i8::MAX as usize => { + // For add m64, imm8, the immediate is sign-extend and + // hence treated as signed. + asm.add( + MemOp::IndirectBaseIndex(dmem_base, dmem_idx), + Imm8::from(cnt as u8), + ); + + // Advance pc, but account for pc increment at the end + // of the loop. + pc += cnt - 1; + } + cnt @ _ => unimplemented!("cnt={cnt} oob, add with larger imm"), + } } '-' => { - asm.dec(MemOp8::from(MemOp::IndirectBaseIndex(dmem_base, dmem_idx))); + // Apply optimization to fold consecutive '-' instructions to a + // single sub instruction during compile time. + + match vm.imem[pc..].iter().take_while(|&&i| i.eq(&'-')).count() { + 1 => asm.dec(MemOp8::from(MemOp::IndirectBaseIndex(dmem_base, dmem_idx))), + cnt if cnt <= i8::MAX as usize => { + // For sub m64, imm8, the immediate is sign-extend and + // hence treated as signed. + asm.sub( + MemOp::IndirectBaseIndex(dmem_base, dmem_idx), + Imm8::from(cnt as u8), + ); + + // Advance pc, but account for pc increment at the end + // of the loop. + pc += cnt - 1; + } + cnt @ _ => unimplemented!("cnt={cnt} oob, sub with larger imm"), + } } '.' => { // Load data memory from active cell into di register, which is @@ -254,6 +291,9 @@ fn run_jit(prog: &str) { } _ => unreachable!(), } + + // Increment pc to next instruction. + pc += 1; } // Return from bf program. |