Add loop syntactic sugar; errors now use print instead of debug; add check for duplicate labels.

README.md

@@ -408,6 +408,36 @@ to a varying number of skips and conditional instructions by the assembler. Only
 
 Jumping to a label is always safer than a manual skip.
 
+### Loop syntactic sugar
+
+Infinite loops are a very common construct, so there is special syntax added for them.
+
+These are converted by the assembler to an anonymous label and a jump to it.
+
+```
+(loop
+    ...ops
+)
+```
+
+If you want to have a convenient jump target, give the loop a name. This lets you easily "break" and "continue" 
+by jumping to the labels.
+
+```
+(loop :label
+    ...ops
+)
+```
+
+becomes
+
+```
+(:label)
+...ops
+(j :label)
+(:label-end)
+```
+
 ## Built-in Instructions
 
 ...and pseudo-instructions

crsn/src/asm/error.rs

@@ -12,13 +12,13 @@ use crate::asm::instr::Cond;
 /// csn_asm unified error type
 #[derive(Error, Debug)]
 pub enum CrsnError {
-    #[error("S-expression parsing error: {0:?}")]
+    #[error("S-expression parsing error: {0}")]
     Sexp(#[from] Box<sexp::Error>),
-    #[error("Parse error: {0:?} at {1:?}")]
+    #[error("Parse error: {0} at {1}")]
     Parse(Cow<'static, str>, SourcePosition),
-    #[error("Parse error: {0:?} at {1:?}")]
+    #[error("Parse error: {0} at {1}")]
     ParseOther(Box<dyn Error + Send + Sync>, SourcePosition),
-    #[error("Assembler error: {0:?} at {1:?}")]
+    #[error("Assembler error: {0} at {1}")]
     Asm(AsmError, SourcePosition),
 }
 
@@ -33,8 +33,10 @@ pub enum AsmError {
     DiscardAsValue,
     #[error("Conditional branch already defined for \"{0}\"")]
     ConditionalAlreadyUsed(Cond),
-    #[error("Label \"{0:?}\" not defined")]
+    #[error("Label \"{0}\" not defined")]
     LabelNotDefined(Label),
+    #[error("Label \"{0}\" already defined in this scope")]
+    LabelDuplicate(Label),
     #[error("Bad register type: {0}")]
     BadRegisterType(Register),
 }

crsn/src/asm/instr/flatten.rs

@@ -174,6 +174,10 @@ pub fn jumps_to_skips(ops: Vec<Op>) -> Result<Vec<Op>, CrsnError> {
     let mut label_positions = HashMap::<Label, usize>::new();
     for (n, op) in ops.iter().enumerate() {
         if let OpKind::BuiltIn(BuiltinOp::Label(name)) = &op.kind {
+            if label_positions.contains_key(name) {
+                return Err(CrsnError::Asm(AsmError::LabelDuplicate(name.clone()), op.pos.clone()));
+            }
+
             label_positions.insert(name.clone(), n - label_positions.len());
         }
     }

crsn/src/asm/parse/arg_parser.rs

@@ -109,7 +109,7 @@ impl<'a> TokenParser<'a> {
     }
 
     /// Look at the next entry
-    pub fn peek(&mut self) -> Option<&Sexp> {
+    pub fn peek(&self) -> Option<&Sexp> {
         self.args.last()
     }
 

crsn/src/builtin/mod.rs

@@ -1,15 +1,16 @@
-use sexp::SourcePosition;
+use sexp::{SourcePosition, Sexp, Atom};
 
 use crate::asm::error::CrsnError;
 use crate::asm::instr::op::OpKind;
 use crate::asm::parse::arg_parser::TokenParser;
 use crate::module::{CrsnExtension, ParseRes};
-use crate::asm::data::literal::Value;
+use crate::asm::data::literal::{Value, Label};
 use crate::asm::instr::{Flatten, Op};
 use crate::asm::parse::parse_instructions;
 use crate::builtin::defs::BuiltinOp;
 use crate::asm::instr::flatten::jumps_to_skips;
 use crate::asm::data::{Rd, RdData};
+use crate::asm::parse::parse_data::parse_label;
 
 pub mod defs;
 pub mod exec;
@@ -47,7 +48,7 @@ impl CrsnExtension for BuiltinOps {
     /// Parse a generic S-expression (non-op) that started with the given keyword
     ///
     /// pcx is available on the arg_tokens parser
-    fn parse_syntax<'a>(&self, pos: &SourcePosition, keyword: &str, tokens: TokenParser<'a>)
+    fn parse_syntax<'a>(&self, pos: &SourcePosition, keyword: &str, mut tokens: TokenParser<'a>)
                         -> Result<ParseRes<'a, Box<dyn Flatten>>, CrsnError>
     {
         if keyword == "crit" || keyword == "critical" {
@@ -91,19 +92,59 @@ impl CrsnExtension for BuiltinOps {
                 Box::new(Op {
                     kind: OpKind::BuiltIn(BuiltinOp::CriticalBegin),
                     cond: None,
-                    pos: pos.clone()
+                    pos: pos.clone(),
                 }),
                 Box::new(flattened),
                 Box::new(Op {
                     kind: OpKind::BuiltIn(BuiltinOp::CriticalEnd),
                     cond: None,
-                    pos: pos.clone()
+                    pos: pos.clone(),
-                })
+                }),
             ];
 
             return Ok(ParseRes::Parsed(Box::new(vec)));
         }
 
+        if keyword == "loop" {
+            let mut end_label = None;
+            let label = if let Some(Sexp::Atom(Atom::S(_), _)) = tokens.peek() {
+                let label = parse_label(tokens.next().unwrap())?;
+                if let Label::Named(n) = &label {
+                    end_label = Some(Label::Named(format!("{}-end", n)));
+                }
+                label
+            } else {
+                Label::unique(&tokens.pcx.state.borrow().label_num)
+            };
+
+            let pcx = tokens.pcx;
+            let inner = parse_instructions(tokens.into_iter(), pos, pcx)?;
+
+            let mut vec : Vec<Box<dyn Flatten>> = vec![
+                Box::new(Op {
+                    kind: OpKind::BuiltIn(BuiltinOp::Label(label.clone())),
+                    cond: None,
+                    pos: pos.clone(),
+                }),
+                inner,
+                Box::new(Op {
+                    kind: OpKind::BuiltIn(BuiltinOp::Jump(label)),
+                    cond: None,
+                    pos: pos.clone(),
+                }),
+            ];
+
+            if let Some(el) = end_label {
+                vec.push(Box::new(Op {
+                    kind: OpKind::BuiltIn(BuiltinOp::Label(el)),
+                    cond: None,
+                    pos: pos.clone(),
+                }));
+            }
+
+            return Ok(ParseRes::Parsed(Box::new(vec)))
+        }
+
         Ok(ParseRes::Unknown(tokens))
     }
 }

crsn_stdio/src/lib.rs

@@ -14,7 +14,6 @@ use std::io;
 use crsn::asm::instr::cond::Flag;
 use std::fmt;
 use crsn::asm::data::Wr;
-use std::time::Instant;
 
 mod console {
     use std::{io};
@@ -23,7 +22,7 @@ mod console {
     use std::ffi::c_void;
     use std::mem::{self, MaybeUninit};
     use crsn::runtime::fault::Fault;
-    use std::time::{Duration, Instant};
+    use std::time::{Instant};
 
     struct ReadCharState {
         bytes: [u8; 4],

examples/loop.csn

@@ -0,0 +1,43 @@
+(
+    ; Unlabeled loop. Can be exited by jumping out
+
+    (loop
+        (nop)
+        (nop)
+        (nop)
+    )
+
+    (barrier)
+
+    ; The above is equivalent to:
+
+    (:label)
+    (nop)
+    (nop)
+    (nop)
+    (j :label)
+
+    (barrier)
+
+    ; The label name can be specified.
+    ; This adds a start label and ":label-end" at the end of the loop:
+
+    (loop :repeat
+        (nop)
+        (nop)
+        (j :repeat-end)
+        (nop)
+    )
+
+    (barrier)
+
+    ; The above is equivalent to: (labels changed to avoid a compile error)
+
+    (:repeat2)
+    (nop)
+    (nop)
+    (j :repeat2-end)
+    (nop)
+    (j :repeat2)
+    (:repeat2-end)
+)