Merge branch 'consteval'

README.md

@@ -196,6 +196,35 @@ Some instructions use bit offsets and widths. Width is directly attached to the
 offsets are attached at the respective arguments after a colon: `(ld16 r0:8 r1:32)`  -
 load 16 bits, starting at offset 32 of `r1`, into `r0`, starting at offset 8. The rest if the register is not affected.
 
+### Compile-time arithmetics
+
+Quite often you will want to do some calculations at compile time, for example to create a constant whose value depends on another,
+or to compose a binary value using bit shifts and masking. This can be done in any place that expects an input operand (`Rd`).
+
+The syntax for this is as follows:
+
+```
+(ld r0 (=add 123 456))
+```
+
+The expressions can be nested. The equals sign is not required in the inner levels, and the output operand must be omitted 
+(the compiler inserts a placeholder register there during evaluation):
+
+```
+(def WIDTH 1024)
+(def HALFW_MAX (=sub (div WIDTH 2) 1))
+```
+
+Almost any instruction can be evaluated this way, excluding instructions that perform IO, work with the screen, objects etc.
+Instructions that are not compile-time evaluation safe will produce a compile error.
+
+There are several limitations to consider:
+
+- Only immediate values (literals) and constant names may be used.
+- Registers, if used, will always read as zero and writes have no effect. (This should also produce an error)
+- Only instructions that take the form `(op Wr ...)` can be used. The `Wr` operand is inserted automatically and must NOT be specified!
+- Conditionals are not allowed inside expressions: branches, conditional suffixes
+
 ### Conditional branches
 
 Conditonal branches are written like this:
@@ -296,7 +325,9 @@ Jumping to a label is always safer than a manual skip.
 ; However, if the register is a global register, then the alias is valid everywhere.
 (sym SYM REG)
 
-; Define a constant. These are valid in the whole program.
+; Define a constant. These are valid in the entire program following the definition point, unless
+; un-defined. Constants are evaluated and assigned at compile time, the program control flow has no
+; effect.
 ; Value must be known at compile time.
 (def CONST VALUE)
 

compile_examples.sh

@@ -4,8 +4,4 @@ set -e
 
 cargo build
 
-for file in examples/*.csn
-do
-  echo "--- $file ---"
-  target/debug/launcher -P "$file"
-done
+find examples -name '*.csn' -type f -exec target/debug/launcher -P {} \;

crsn/crsn-sexp/src/error.rs

@@ -1,4 +1,5 @@
 use std::{cmp, fmt};
+use std::fmt::{Formatter, Debug};
 
 /// The representation of an s-expression parse error.
 pub struct Error {
@@ -9,7 +10,7 @@ pub struct Error {
 }
 
 /// Position in the input string
-#[derive(Debug, PartialEq, Clone, Default)]
+#[derive(PartialEq, Clone, Default)]
 pub struct SourcePosition {
     /// The line number on which the error occurred.
     pub line: u32,
@@ -25,6 +26,21 @@ impl fmt::Display for SourcePosition {
     }
 }
 
+impl Debug for SourcePosition {
+    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
+        if f.alternate() {
+            f.debug_struct("SourcePosition")
+                .field("line", &self.line)
+                .field("column", &self.column)
+                .field("index", &self.index)
+                .finish()
+        } else {
+            // shorter version
+            write!(f, "Pos({}:{})", self.line, self.column)
+        }
+    }
+}
+
 /// Since errors are the uncommon case, they're boxed. This keeps the size of
 /// structs down, which helps performance in the common case.
 ///

crsn/src/asm/instr/op.rs

@@ -65,4 +65,11 @@ impl OpTrait for Op {
 
         se
     }
+
+    fn is_compile_time_evaluable(&self) -> bool {
+         match &self.kind {
+            OpKind::BuiltIn(op) => op.is_compile_time_evaluable(),
+            OpKind::Ext(op) => op.is_compile_time_evaluable()
+        }
+    }
 }

crsn/src/asm/mod.rs

@@ -8,6 +8,8 @@ use crate::asm::parse::{ParserContext, ParserState};
 use crate::module::{CrsnExtension, CrsnUniq};
 use crate::runtime::program::Program;
 use crate::builtin::BuiltinOps;
+use crate::runtime::run_thread::{RunState, ThreadInfo, ThreadToken};
+use crate::runtime::frame::REG_COUNT;
 
 pub mod data;
 pub mod error;
@@ -18,11 +20,12 @@ pub mod patches;
 /// Parse a program from string and assemble a low level instruction sequence from it.
 pub fn assemble(source: &str, uniq : &CrsnUniq, mut parsers: Vec<Box<dyn CrsnExtension>>) -> Result<Arc<Program>, error::CrsnError> {
     parsers.insert(0, BuiltinOps::new());
-
     for p in &mut parsers {
         p.init(uniq);
     }
 
+    let parsers_arc = Arc::new(parsers);
+
     // remove first line if it looks like a shebang
     let source = if source.starts_with("#!") {
         if let Some(nl) = source.find('\n') {
@@ -34,18 +37,38 @@ pub fn assemble(source: &str, uniq : &CrsnUniq, mut parsers: Vec<Box<dyn CrsnExt
         source
     };
 
+    let ti = Arc::new(ThreadInfo {
+        id: ThreadToken(0),
+        uniq: Default::default(),
+        program: Program::new(vec![], parsers_arc.clone()).unwrap(),
+        cycle_time: Default::default(),
+        extensions: parsers_arc.clone(),
+    });
+
     let pcx = ParserContext {
-        parsers: &parsers,
+        parsers: &parsers_arc,
         state: RefCell::new(ParserState {
             reg_aliases: Default::default(),
             reg_alias_stack: vec![],
             global_reg_aliases: Default::default(),
             constants: Default::default(),
+
+            // This is a fake thread to pass to constant expressions when evaluating them.
+            // This allows to evaluate nearly all instructions at compile time.
+            const_eval: RunState {
+                thread_info: ti.clone(),
+                frame: Default::default(),
+                call_stack: vec![],
+                global_regs: [0; REG_COUNT],
+                ext_data: Default::default()
+            },
+            const_eval_ti: ti,
+            parsing_expr: false
         }),
     };
 
     let ops = parse::parse(source, &SourcePosition::default(), &pcx)?;
     let ops = labels_to_skips(ops)?;
 
-    Ok(Program::new(ops, Arc::new(parsers))?)
+    Ok(Program::new(ops, parsers_arc)?)
 }

crsn/src/asm/parse/arg_parser.rs

@@ -8,9 +8,10 @@ use crate::asm::parse::sexp_expect::expect_string_atom;
 use crate::asm::data::literal::Value;
 use crate::builtin::defs::BitMask;
 use crate::asm::patches::ErrWithPos;
+use std::fmt::{Debug, Formatter};
+use std::fmt;
 
 /// Utility for argument parsing
-#[derive(Debug)]
 pub struct TokenParser<'a> {
     orig_len: usize,
     args: Vec<Sexp>,
@@ -18,6 +19,16 @@ pub struct TokenParser<'a> {
     pub pcx: &'a ParserContext<'a>,
 }
 
+impl<'a> Debug for TokenParser<'a> {
+    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
+        f.debug_struct("TokenParser")
+            .field("orig_len", &self.orig_len)
+            .field("args", &self.args)
+            .field("start_pos", &self.start_pos)
+            .finish()
+    }
+}
+
 impl<'a> IntoIterator for TokenParser<'a> {
     type Item = Sexp;
     type IntoIter = std::vec::IntoIter<Sexp>;
@@ -42,6 +53,13 @@ impl<'a> TokenParser<'a> {
         }
     }
 
+    /// Prepend a token
+    pub fn prepend(&mut self, what: Sexp) {
+        // the list is reversed - actually, append it
+        self.args.push(what);
+        self.orig_len += 1;
+    }
+
     /// Get error if not empty.
     /// The argument is substituted into the phrase "Instruction needs ...!" - i.e. "one Wr argument and a list or string"
     pub fn ensure_empty(&self, what_arguments : &str) -> Result<(), CrsnError> {

crsn/src/asm/parse/mod.rs

@@ -11,6 +11,8 @@ use crate::asm::error::CrsnError;
 use crate::asm::instr::Op;
 use crate::asm::parse::sexp_expect::expect_list;
 use crate::module::CrsnExtension;
+use crate::runtime::run_thread::{ThreadInfo, RunState};
+use std::sync::Arc;
 
 pub mod parse_cond;
 pub mod parse_instr;
@@ -28,7 +30,7 @@ pub struct ParserContext<'a> {
     pub state: RefCell<ParserState>,
 }
 
-#[derive(Default, Debug)]
+#[derive(Debug)]
 pub struct ParserState {
     /// Register aliases valid globally
     pub global_reg_aliases: HashMap<RegisterAlias, Register>,
@@ -41,6 +43,14 @@ pub struct ParserState {
 
     /// Global constants
     pub constants: HashMap<ConstantName, Value>,
+
+    /// Dummy run state used for const eval
+    pub const_eval: RunState,
+    // ThreadInfo is needed separately from RunState. TODO check if this can be refactored
+    pub const_eval_ti: Arc<ThreadInfo>,
+
+    /// True if we are in an expression parser context
+    pub parsing_expr : bool,
 }
 
 pub fn parse(source: &str, pos: &SourcePosition, parsers: &ParserContext) -> Result<Vec<Op>, CrsnError> {

crsn/src/asm/parse/parse_data.rs

@@ -3,12 +3,15 @@ use std::convert::TryFrom;
 
 use sexp::{Atom, Sexp, SourcePosition};
 
-use crate::asm::data::{DataDisp, Rd, RdData, reg, Wr, WrData, RdWr};
+use crate::asm::data::{DataDisp, Rd, RdData, reg, Wr, WrData, RdWr, Register};
 use crate::asm::data::literal::{ConstantName, Label, RegisterAlias, Value};
 use crate::asm::error::CrsnError;
-use crate::asm::parse::ParserContext;
+use crate::asm::parse::{ParserContext, parse_instructions};
 use crate::asm::parse::sexp_expect::expect_string_atom;
 use crate::asm::patches::ErrWithPos;
+use std::sync::atomic::AtomicU32;
+use crate::module::OpTrait;
+use crate::asm::instr::Cond;
 
 fn is_valid_identifier(name: &str) -> bool {
     // ascii symbols "!\"#$_&'()*+,-./:;<=>?@[\\]^_`{|}~"
@@ -72,6 +75,7 @@ pub fn parse_label_str(name: &str, pos: &SourcePosition) -> Result<Label, CrsnEr
 pub fn parse_data_disp(tok: Sexp, pcx: &ParserContext) -> Result<DataDisp, CrsnError> {
     // trace!("parse data: {:?}", tok);
     match tok {
+        // immediates are okay in const eval - no tests needed
         Sexp::Atom(Atom::I(val), _pos) => {
             Ok(DataDisp::Immediate(unsafe { std::mem::transmute(val) }))
         }
@@ -87,7 +91,57 @@ pub fn parse_data_disp(tok: Sexp, pcx: &ParserContext) -> Result<DataDisp, CrsnE
         Sexp::Atom(Atom::QS(_s), pos) => {
             Err(CrsnError::Parse("Quoted string not expected here".into(), pos))
         }
-        Sexp::List(_list, pos) => {
+        Sexp::List(list, pos) => {
+            if let Some(Sexp::Atom(Atom::S(s), s_pos)) = list.first() {
+                // Const eval
+
+                let parsing_expr = pcx.state.borrow().parsing_expr;
+
+                if !s.starts_with('=') && !parsing_expr {
+                    return Err(CrsnError::Parse(format!("Invalid syntax, did you mean \"={}\" (a compile-time expression)?", s).into(), s_pos.clone()));
+                }
+
+                // start expr parsing mode
+                let orig_parsing_expr = pcx.state.borrow().parsing_expr;
+                pcx.state.borrow_mut().parsing_expr = true;
+
+                let lmut = AtomicU32::new(0);
+
+                let mut expr_ops = parse_instructions(
+                    // TODO avoid this madness
+                    vec![Sexp::List(list, pos.clone())].into_iter(),
+                    &pos, pcx)?
+                    .flatten(&lmut)?;
+
+                if expr_ops.len() != 1 {
+                    return Err(CrsnError::Parse(format!("Expected one top level operation in an expression, got: {:?}", expr_ops).into(), pos.clone()));
+                }
+
+                let op = expr_ops.remove(0);
+
+                if !op.is_compile_time_evaluable() {
+                    return Err(CrsnError::Parse(format!("Instruction {} cannot be used in an expression!", op.to_sexp()).into(), pos.clone()));
+                }
+
+                let mut state_mut = pcx.state.borrow_mut();
+                state_mut.const_eval.clear_all();
+
+                let ticl = state_mut.const_eval.thread_info.clone();
+                op.execute(&ticl, &mut state_mut.const_eval)
+                    .map_err(|f| CrsnError::ParseOther(Box::new(f), pos.clone()))?;
+
+                if state_mut.const_eval.test_cond(Cond::Invalid) {
+                    return Err(CrsnError::Parse("Expression evaluation failed - invalid flag set!".into(), pos.clone()));
+                }
+
+                if !orig_parsing_expr {
+                    // exit expr parsing mode
+                    state_mut.parsing_expr = false;
+                }
+
+                return Ok(DataDisp::Immediate(state_mut.const_eval.frame.gen[0]));
+            }
+
             Err(CrsnError::Parse("List not expected here".into(), pos))
         }
         Sexp::Atom(Atom::S(s), pos) => {
@@ -97,12 +151,16 @@ pub fn parse_data_disp(tok: Sexp, pcx: &ParserContext) -> Result<DataDisp, CrsnE
 }
 
 /// Parse data disp from a string token (a &str is used so the string can be preprocessed)
-pub fn parse_data_disp_from_str(s: &str, pos: &SourcePosition, pcx: &ParserContext) -> Result<DataDisp, CrsnError> {
+fn parse_data_disp_from_str(s: &str, pos: &SourcePosition, pcx: &ParserContext) -> Result<DataDisp, CrsnError> {
     if s == "_" {
         return Ok(DataDisp::Discard);
     }
 
     if let Some(reference) = s.strip_prefix('@') {
+        if pcx.state.borrow().parsing_expr {
+            return Err(CrsnError::Parse("Object handles cannot be used in expressions!".into(), pos.clone()));
+        }
+
         /* extension constants (pre-defined handles) */
         for p in pcx.parsers {
             if let Some(val) = p.get_constant_value(reference) {
@@ -141,7 +199,7 @@ pub fn parse_data_disp_from_str(s: &str, pos: &SourcePosition, pcx: &ParserConte
             return Ok(DataDisp::Immediate(*val));
         }
 
-        /* register aliases */
+        /* register aliases - no need to check for const_eval, the aliases could never be defined */
         if let Some(val) = pstate.reg_aliases.get(s) {
             return Ok(DataDisp::Register(*val));
         } else if let Some(val) = pstate.global_reg_aliases.get(s) {
@@ -168,6 +226,14 @@ pub fn parse_data_disp_from_str(s: &str, pos: &SourcePosition, pcx: &ParserConte
             }
         }
 
+        if pcx.state.borrow().parsing_expr {
+            if s == "=result" {
+                return Ok(DataDisp::Register(Register::Gen(0)));
+            } else {
+                return Err(CrsnError::Parse("Registers cannot be used in expressions!".into(), pos.clone()));
+            }
+        }
+
         /* register */
         let reg = reg::parse_reg(&s, &pos)?;
 
@@ -184,39 +250,13 @@ pub fn parse_data_disp_from_str(s: &str, pos: &SourcePosition, pcx: &ParserConte
 
 /// Parse immediate value
 pub fn parse_value(tok: Sexp, pcx: &ParserContext) -> Result<(Value, SourcePosition), CrsnError> {
-    match tok {
-        Sexp::Atom(Atom::I(val), pos) => {
-            Ok((unsafe { std::mem::transmute(val) }, pos))
-        }
-        Sexp::Atom(Atom::U(val), pos) => {
-            Ok((val, pos))
-        }
-        Sexp::Atom(Atom::C(val), pos) => {
-            Ok((val as u64, pos))
-        }
-        Sexp::Atom(Atom::QS(_), pos) => {
-            Err(CrsnError::Parse("quoted string not expected here".into(), pos))
-        }
-        Sexp::Atom(Atom::F(val), pos) => {
-            Ok((unsafe { std::mem::transmute(val) }, pos))
-        }
-        Sexp::Atom(Atom::S(s), pos) => {
-            let pstate = pcx.state.borrow();
-            if let Some(val) = pstate.constants.get(&s) {
-                return Ok((*val, pos));
-            }
+    let pos = tok.pos().clone();
+    let parsed = parse_rd(tok, pcx)?;
 
-            /* extension constants */
-            for p in pcx.parsers {
-                if let Some(val) = p.get_constant_value(&s) {
-                    return Ok((val, pos));
-                }
-            }
-
-            Err(CrsnError::Parse(format!("unknown constant: {}", s).into(), pos))
-        }
-        Sexp::List(_, pos) => {
-            Err(CrsnError::Parse("expected a value".into(), pos))
+    match parsed {
+        Rd(RdData::Immediate(value)) => Ok((value, pos)),
+        _ => {
+            Err(CrsnError::Parse("expected an immediate value".into(), pos))
         }
     }
 }

crsn/src/asm/parse/parse_instr.rs

@@ -1,4 +1,4 @@
-use sexp::{Sexp, SourcePosition, Atom};
+use sexp::{Sexp, SourcePosition, Atom, atom_s};
 
 use crate::asm::error::CrsnError;
 use crate::asm::instr::{Flatten, InstrWithBranches};
@@ -18,9 +18,20 @@ pub fn parse_instructions(items: impl Iterator<Item=Sexp>, pos: &SourcePosition,
         let (tokens, listpos) = expect_list(expr, false)?;
 
         let mut toki = tokens.into_iter();
-        let (name, namepos) = expect_string_atom(toki.next_or_err(listpos.clone(), "Expected instruction name token")?)?;
+        let (mut name, namepos) = expect_string_atom(toki.next_or_err(listpos.clone(), "Expected instruction name token")?)?;
+
+        let parsing_expr = pcx.state.borrow().parsing_expr;
+
+        if parsing_expr {
+            if let Some(n) = name.strip_prefix('=') {
+                name = n.to_string();
+            }
+        }
 
         if name == "proc" {
+            if parsing_expr {
+                return Err(CrsnError::Parse("Illegal syntax in const expression".into(), pos.clone()));
+            }
             parsed.push(parse_routine(toki, pos, pcx)?);
             continue;
         }
@@ -62,8 +73,13 @@ pub fn parse_instructions(items: impl Iterator<Item=Sexp>, pos: &SourcePosition,
             })
             .collect::<Vec<_>>();
 
-        let arg_tokens = TokenParser::new(toki.take(token_count - branch_tokens.len()).collect(), &listpos, pcx);
-        // debug!("branch_tokens: {:#?}", branch_tokens);
+        if parsing_expr && !branch_tokens.is_empty() {
+            return Err(CrsnError::Parse(format!("Conditional branches are not allowed in const expression: {:?}", branch_tokens).into(), pos.clone()));
+        }
+
+        let mut arg_parser = TokenParser::new(toki.take(token_count - branch_tokens.len()).collect(), &listpos, pcx);
+
+        trace!("Parse op: {}\nargs {:?}\nbranches {:?}", name, arg_parser, branch_tokens);
 
         let branches = {
             let mut branches = vec![];
@@ -77,7 +93,12 @@ pub fn parse_instructions(items: impl Iterator<Item=Sexp>, pos: &SourcePosition,
             }
         };
 
-        if let Some(op) = parse_op(name.as_str(), arg_tokens, &namepos)? {
+        if parsing_expr {
+            // hackity hack for const expr eval
+            arg_parser.prepend(atom_s("=result"));
+        }
+
+        if let Some(op) = parse_op(name.as_str(), arg_parser, &namepos)? {
             parsed.push(Box::new(InstrWithBranches {
                 op,
                 pos: namepos,

crsn/src/asm/parse/parse_op.rs

@@ -16,6 +16,10 @@ pub fn parse_op<'a>(mut keyword: &str, mut arg_tokens: TokenParser<'a>, spos: &S
         keyword = &keyword[..pos];
     }
 
+    if cond.is_some() && arg_tokens.pcx.state.borrow().parsing_expr {
+        return Err(CrsnError::Parse("Conditional suffixes are not allowed in const expression".into(), spos.clone()));
+    }
+
     for p in arg_tokens.pcx.parsers {
         arg_tokens = match p.parse_op(spos, keyword, arg_tokens) {
             Ok(ParseRes::Parsed(kind)) => return Ok(Some(Op {

crsn/src/builtin/exec.rs

@@ -204,6 +204,13 @@ impl OpTrait for BuiltinOp {
         Ok(res)
     }
 
+    fn is_compile_time_evaluable(&self) -> bool {
+        match self {
+            BuiltinOp::Load { .. } | BuiltinOp::LoadBits { .. } => true,
+            _ => false
+        }
+    }
+
     fn to_sexp(&self) -> Sexp {
         super::parse::to_sexp(self)
     }

crsn/src/module/mod.rs

@@ -48,11 +48,18 @@ pub trait OpTrait: Debug + Send + Sync + 'static {
 
     /// Turn into an S-expression that produces this instruction when parsed
     fn to_sexp(&self) -> Sexp;
+
+    /// Check if an operation is safe to use in compile-time arithmetics - has no side effects
+    /// outside the input and output registers (and flags), has the form (op Wr ...), and does not
+    /// use object handles or extension data.
+    fn is_compile_time_evaluable(&self) -> bool {
+        false
+    }
 }
 
 /// CRSN initializer object.
 /// Only one should be created for the lifespan of the parser and runtime.
-#[derive(Default)]
+#[derive(Default,Debug)]
 pub struct CrsnUniq {
     object_handle_counter : AtomicU64
 }

crsn/src/runtime/run_thread/info.rs

@@ -7,6 +7,7 @@ use crate::runtime::program::Program;
 use crate::runtime::run_thread::ThreadToken;
 use crate::module::{CrsnExtension, CrsnUniq};
 
+#[derive(Debug)]
 pub struct ThreadInfo {
     /// Thread ID
     pub id: ThreadToken,

crsn/src/runtime/run_thread/state.rs

@@ -25,6 +25,16 @@ pub struct RunState {
     pub ext_data: ExtensionDataStore,
 }
 
+impl RunState {
+    /// Clear everything. Caution: when done at runtime, this effectively reboots the thread
+    pub fn clear_all(&mut self) {
+        self.frame = Default::default();
+        self.call_stack = Default::default();
+        self.global_regs = Default::default();
+        self.ext_data = Default::default();
+    }
+}
+
 impl Debug for RunState {
     fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
         f.debug_struct("RunState")

crsn_arith/src/exec.rs

@@ -757,6 +757,15 @@ impl OpTrait for ArithOp {
             ArithOp::FloatHypAcot { dst, a } => to_sexp_1_or_2("facoth", dst, a),
         }
     }
+
+    fn is_compile_time_evaluable(&self) -> bool {
+        match self {
+            ArithOp::Test { .. } | ArithOp::Compare { .. } | ArithOp::RangeTest { .. }
+            | ArithOp::FloatTest { .. } | ArithOp::FloatCompare { .. } | ArithOp::FloatRangeTest { .. } => false,
+            // rng is allowed... makes little sense, but it also has no side effects
+            _ => true, // a bold claim...
+        }
+    }
 }
 
 fn to_sexp_2_or_3(name: &str, dst: &Wr, a: &Rd, b: &Rd) -> Sexp {

examples/expr.csn

@@ -0,0 +1,15 @@
+(
+    (def A 10)
+    (def FOO (=add A (sub 10 5)))
+
+    ; FOO is 15
+
+    (ld r0 (=add 14 1))
+    (cmp r0 15 (ne? (fault "1")))
+
+    (ld r0 (=add FOO 1))
+    (cmp r0 16 (ne? (fault "2")))
+
+    (ld r0 (=add (sub FOO 2) 3))
+    (cmp r0 16 (ne? (fault "3")))
+)

launcher/src/main.rs

@@ -151,6 +151,7 @@ fn main() -> anyhow::Result<()> {
     ])?;
 
     if config.assemble_only {
+        println!("--- {} ---", config.program_file);
         for (n, op) in parsed.ops.iter().enumerate() {
             if config.assemble_debug {
                 println!("{:04} : {:?}", n, op);