add opt that doesn't make anything faster but might allow better opts later

rust2/src/codegen.rs

@@ -31,6 +31,7 @@ pub enum Stmt {
     Out,
     In,
     SetNull,
+    SetN(u8),
     JmpIfZero(u32),
     JmpIfNonZero(u32),
     End,
@@ -84,6 +85,7 @@ fn ir_to_stmt<'c>(code: &mut Code<'c>, ir_stmt: &IrStmt<'_>) {
         StmtKind::Out => Stmt::Out,
         StmtKind::In => Stmt::In,
         StmtKind::SetNull => Stmt::SetNull,
+        StmtKind::SetN(n) => Stmt::SetN(*n),
         StmtKind::Loop(instr) => {
             let skip_jmp_idx = code.stmts.len();
             code.stmts.push(Stmt::JmpIfZero(0)); // placeholder

rust2/src/codegen_interpreter.rs

@@ -87,6 +87,9 @@ where
                 Stmt::SetNull => {
                     *self.elem_mut() = Wrapping(0);
                 }
+                Stmt::SetN(n) => {
+                    *self.elem_mut() = Wrapping(n);
+                }
                 Stmt::JmpIfZero(pos) => {
                     if self.elem() == 0 {
                         self.ip = pos as usize;

rust2/src/lib.rs

@@ -1,7 +1,6 @@
 #![feature(allocator_api, let_else)]
 #![deny(unsafe_op_in_unsafe_fn)]
 #![warn(rust_2018_idioms)]
-#![allow(dead_code)]
 
 use crate::parse::ParseError;
 use bumpalo::Bump;

rust2/src/main.rs

@@ -20,7 +20,12 @@ fn main() {
     let stdin = io::stdin();
     let stdin = stdin.lock();
 
-    brainfuck::run(&file, stdout, stdin, UseProfile::Yes).unwrap_or_else(|_| {
+    let profile = env::args()
+        .any(|a| a == "--profile")
+        .then(|| UseProfile::Yes)
+        .unwrap_or(UseProfile::No);
+
+    brainfuck::run(&file, stdout, stdin, profile).unwrap_or_else(|_| {
         eprintln!("error: Failed to parse brainfuck code");
         process::exit(1);
     });

rust2/src/opts.rs

@@ -14,11 +14,12 @@ pub struct Stmt<'ir> {
 }
 
 impl<'ir> Stmt<'ir> {
-    fn lol(kind: StmtKind<'ir>) -> Stmt<'ir> {
-        Self {
-            kind,
-            span: Span::default(),
-        }
+    fn new(kind: StmtKind<'ir>, span: Span) -> Stmt<'ir> {
+        Self { kind, span }
+    }
+
+    fn kind(&self) -> &StmtKind<'ir> {
+        &self.kind
     }
 }
 
@@ -32,12 +33,14 @@ pub enum StmtKind<'ir> {
     Out,
     In,
     SetNull,
+    SetN(u8),
 }
 
 pub fn optimize<'ir>(alloc: &'ir Bump, instrs: &[(Instr<'_>, Span)]) -> Ir<'ir> {
     let ir = ast_to_ir(alloc, instrs);
     let mut ir = pass_group(alloc, ir);
     pass_find_set_null(&mut ir);
+    pass_set_n(&mut ir);
     ir
 }
 
@@ -57,7 +60,7 @@ fn ast_to_ir<'ir>(alloc: &'ir Bump, ast: &[(Instr<'_>, Span)]) -> Ir<'ir> {
                 StmtKind::Loop(ir_body)
             }
         };
-        Stmt { kind, span: *span }
+        Stmt::new(kind, *span)
     });
 
     stmts.extend(stmts_iter);
@@ -65,6 +68,7 @@ fn ast_to_ir<'ir>(alloc: &'ir Bump, ast: &[(Instr<'_>, Span)]) -> Ir<'ir> {
     Ir { stmts }
 }
 
+/// pass that replaces things like `Sub(1) Sub(1)` with `Sub(2)`
 fn pass_group<'ir>(alloc: &'ir Bump, ir: Ir<'ir>) -> Ir<'ir> {
     let new_stmts = Vec::new_in(alloc);
     let stmts = ir
@@ -74,10 +78,10 @@ fn pass_group<'ir>(alloc: &'ir Bump, ir: Ir<'ir>) -> Ir<'ir> {
             let Some(old) = stmts.last_mut() else {
                 if let StmtKind::Loop(body) = next.kind {
                     let new_body = pass_group(alloc, body);
-                    stmts.push(Stmt {
-                        span: next.span,
-                        kind: StmtKind::Loop(new_body),
-                    });
+                    stmts.push(Stmt::new(
+                         StmtKind::Loop(new_body),
+                        next.span,
+                    ));
                 } else {
                     stmts.push(next);
                 }
@@ -109,10 +113,7 @@ fn pass_group<'ir>(alloc: &'ir Bump, ir: Ir<'ir>) -> Ir<'ir> {
                     });
                 }
                 (_, kind) => {
-                    stmts.push(Stmt {
-                        span: next.span,
-                        kind,
-                    });
+                    stmts.push(Stmt::new(kind, next.span));
                 }
             }
 
@@ -122,6 +123,7 @@ fn pass_group<'ir>(alloc: &'ir Bump, ir: Ir<'ir>) -> Ir<'ir> {
     Ir { stmts }
 }
 
+/// pass that replaces `Loop([Sub(_)])` to `SetNull`
 fn pass_find_set_null(ir: &mut Ir<'_>) {
     for stmt in &mut ir.stmts {
         if let Stmt {
@@ -131,13 +133,37 @@ fn pass_find_set_null(ir: &mut Ir<'_>) {
         {
             if let [Stmt {
                 kind: StmtKind::Sub(_),
-                ..
+                span,
             }] = body.stmts.as_slice()
             {
-                *stmt = Stmt::lol(StmtKind::SetNull);
+                *stmt = Stmt::new(StmtKind::SetNull, *span);
             } else {
                 pass_find_set_null(body);
             }
         }
     }
 }
+
+/// pass that replaces `SetNull Add(5)` with `SetN(5)`
+fn pass_set_n(ir: &mut Ir<'_>) {
+    let stmts = &mut ir.stmts;
+    let mut i = 0;
+    while i < stmts.len() - 1 {
+        let a = &stmts[i];
+        if let StmtKind::SetNull = a.kind() {
+            let b = &stmts[i + 1];
+            let new = match b.kind() {
+                StmtKind::Add(n) => StmtKind::SetN(*n),
+                StmtKind::Sub(n) => StmtKind::SetN(0u8.wrapping_sub(*n)),
+                _ => {
+                    i += 1;
+                    continue;
+                }
+            };
+            let span = a.span.merge(b.span);
+            stmts.remove(i + 1);
+            stmts[i] = Stmt::new(new, span);
+        }
+        i += 1;
+    }
+}

rust2/src/snapshots/brainfuck__parse__tests__nested_loop.snap

@@ -1,6 +1,6 @@
 ---
 source: src/parse.rs
-assertion_line: 132
+assertion_line: 164
 expression: instrs
 ---
 Ok(
@@ -46,14 +46,14 @@ Ok(
                                     ),
                                     Span {
                                         start: 5,
-                                        len: 2,
+                                        len: 3,
                                     },
                                 ),
                             ],
                         ),
                         Span {
                             start: 3,
-                            len: 5,
+                            len: 6,
                         },
                     ),
                     (
@@ -88,7 +88,7 @@ Ok(
             ),
             Span {
                 start: 1,
-                len: 12,
+                len: 13,
             },
         ),
     ],

rust2/src/snapshots/brainfuck__parse__tests__simple.snap

@@ -1,6 +1,6 @@
 ---
 source: src/parse.rs
-assertion_line: 123
+assertion_line: 155
 expression: instrs
 ---
 Ok(
@@ -54,7 +54,7 @@ Ok(
             ),
             Span {
                 start: 5,
-                len: 2,
+                len: 3,
             },
         ),
         (