allow expression in degree statement

airgen/src/lib.rs

@@ -182,7 +182,7 @@ impl<'a> ASMPILConverter<'a> {
             panic!();
         };
 
-        let degree = input.degree.map(|s| s.degree.try_into().unwrap());
+        let degree = input.degree.map(|s| s.degree);
 
         self.submachines = input.submachines;
 

ast/src/asm_analysis/mod.rs

@@ -10,7 +10,6 @@ use std::{
 };
 
 use itertools::Either;
-use powdr_number::BigUint;
 
 use crate::parsed::{
     asm::{
@@ -529,7 +528,7 @@ pub struct OperationSymbol {
 
 #[derive(Clone, Debug)]
 pub struct DegreeStatement {
-    pub degree: BigUint,
+    pub degree: Expression,
 }
 
 #[derive(Clone, Debug)]

ast/src/object/display.rs

@@ -40,7 +40,7 @@ impl Display for PILGraph {
 
 impl Display for Object {
     fn fmt(&self, f: &mut Formatter<'_>) -> Result {
-        if let Some(degree) = self.degree {
+        if let Some(degree) = self.degree.as_ref() {
             writeln!(f, "// Degree {}", degree)?;
         }
         for s in &self.pil {

ast/src/object/mod.rs

@@ -43,7 +43,7 @@ pub enum TypeOrExpression {
 
 #[derive(Default, Clone)]
 pub struct Object {
-    pub degree: Option<u64>,
+    pub degree: Option<Expression>,
     /// the pil identities for this machine
     pub pil: Vec<PilStatement>,
     /// the links from this machine to its children
@@ -57,8 +57,8 @@ pub struct Object {
 }
 
 impl Object {
-    pub fn with_degree(mut self, degree: Option<u64>) -> Self {
-        self.degree = degree;
+    pub fn with_degree<D: Into<Expression>>(mut self, degree: Option<D>) -> Self {
+        self.degree = degree.map(Into::into);
         self
     }
 }

ast/src/parsed/asm.rs

@@ -475,8 +475,8 @@ pub struct Instruction {
 
 #[derive(Debug, PartialEq, Eq, PartialOrd, Ord, Clone)]
 pub enum MachineStatement {
-    Degree(SourceRef, BigUint),
     CallSelectors(SourceRef, String),
+    Degree(SourceRef, Expression),
     Pil(SourceRef, PilStatement),
     Submachine(SourceRef, SymbolPath, String),
     RegisterDeclaration(SourceRef, String, Option<RegisterFlag>),

linker/src/lib.rs

@@ -15,7 +15,7 @@ use powdr_ast::{
 
 use itertools::Itertools;
 
-const DEFAULT_DEGREE: u64 = 1024;
+const DEFAULT_DEGREE: u32 = 1024;
 const MAIN_OPERATION_NAME: &str = "main";
 
 /// a monolithic linker which outputs a single AIR
@@ -27,11 +27,12 @@ pub fn link(graph: PILGraph) -> Result<PILFile, Vec<String>> {
         .get(&main_machine.location)
         .unwrap()
         .degree
-        .unwrap_or(DEFAULT_DEGREE);
+        .clone()
+        .unwrap_or_else(|| DEFAULT_DEGREE.into());
 
     let mut errors = vec![];
 
-    let mut pil = process_definitions(main_degree, graph.definitions);
+    let mut pil = process_definitions(&main_degree, graph.definitions);
 
     for (location, object) in graph.objects.into_iter() {
         if let Some(degree) = object.degree {
@@ -47,7 +48,7 @@ pub fn link(graph: PILGraph) -> Result<PILFile, Vec<String>> {
         pil.push(PilStatement::Namespace(
             SourceRef::unknown(),
             SymbolPath::from_identifier(location.to_string()),
-            Expression::Number(main_degree.into(), None),
+            main_degree.clone(),
         ));
 
         pil.extend(object.pil);
@@ -90,7 +91,7 @@ pub fn link(graph: PILGraph) -> Result<PILFile, Vec<String>> {
 
 // Extract the utilities and sort them into namespaces where possible.
 fn process_definitions(
-    main_degree: u64,
+    main_degree: &Expression,
     definitions: BTreeMap<AbsoluteSymbolPath, TypeOrExpression>,
 ) -> Vec<PilStatement> {
     let mut current_namespace = Default::default();
@@ -125,7 +126,7 @@ fn process_definitions(
                     PilStatement::Namespace(
                         SourceRef::unknown(),
                         namespace.relative_to(&AbsoluteSymbolPath::default()),
-                        Expression::Number(main_degree.into(), None),
+                        main_degree.clone(),
                     ),
                     statement,
                 ]
@@ -306,7 +307,7 @@ mod test {
 
     #[test]
     fn compile_empty_vm() {
-        let expectation = r#"namespace main(8);
+        let expectation = r#"namespace main((4 + 4));
     pol commit _operation_id(i) query std::prover::Query::Hint(2);
     pol constant _block_enforcer_last_step = [0]* + [1];
     let _operation_id_no_change = ((1 - _block_enforcer_last_step) * (1 - instr_return));

parser/src/powdr.lalrpop

@@ -270,7 +270,7 @@ PilStatementInMachine: MachineStatement = {
 }
 
 Degree: MachineStatement = {
-    <start:@L> "degree" <deg:UnsignedInteger> ";" => MachineStatement::Degree(ctx.source_ref(start), deg)
+    <start:@L> "degree" <deg:Expression> ";" => MachineStatement::Degree(ctx.source_ref(start), deg)
 }
 
 CallSelectors: MachineStatement = {

riscv/src/continuations.rs

@@ -235,7 +235,13 @@ pub fn rust_continuations_dry_run<F: FieldElement>(
         .fold(None, |acc, (_, m)| acc.or(m.degree.clone()))
         .unwrap()
         .degree;
-    let length = F::from(length).to_degree() as usize;
+
+    let length: usize = match length {
+        Expression::Number(length, None) => length.try_into().unwrap(),
+        e => unimplemented!(
+            "degree {e} is not supported in continuations as we don't have an evaluator yet"
+        ),
+    };
 
     loop {
         log::info!("\nRunning chunk {}...", chunk_index);

test_data/asm/empty_vm.asm

@@ -1,5 +1,5 @@
 machine VM {
-    degree 8;
+    degree 4 + 4;
 
     reg pc[@pc];
 }