feat!: remove concept of noir fallbacks for foreign functions (#1371)

Author: TomAFrench

crates/noirc_driver/src/lib.rs

@@ -29,6 +29,9 @@ pub use program::CompiledProgram;
 pub struct Driver {
     context: Context,
     language: Language,
+    // We retain this as we need to pass this into `create_circuit` once signature is updated to allow.
+    #[allow(dead_code)]
+    is_opcode_supported: Box<dyn Fn(&Opcode) -> bool>,
 }
 
 #[derive(Args, Clone, Debug, Serialize, Deserialize)]
@@ -68,9 +71,7 @@ impl Default for CompileOptions {
 
 impl Driver {
     pub fn new(language: &Language, is_opcode_supported: Box<dyn Fn(&Opcode) -> bool>) -> Self {
-        let mut driver = Driver { context: Context::default(), language: language.clone() };
-        driver.context.def_interner.set_opcode_support(is_opcode_supported);
-        driver
+        Driver { context: Context::default(), language: language.clone(), is_opcode_supported }
     }
 
     // This is here for backwards compatibility

crates/noirc_frontend/src/ast/function.rs

@@ -76,7 +76,6 @@ impl From<FunctionDefinition> for NoirFunction {
         let kind = match fd.attribute {
             Some(Attribute::Builtin(_)) => FunctionKind::Builtin,
             Some(Attribute::Foreign(_)) => FunctionKind::LowLevel,
-            Some(Attribute::Alternative(_)) => FunctionKind::Normal,
             Some(Attribute::Test) => FunctionKind::Normal,
             None => FunctionKind::Normal,
         };

crates/noirc_frontend/src/hir/mod.rs

@@ -6,7 +6,6 @@ pub mod type_check;
 
 use crate::graph::{CrateGraph, CrateId};
 use crate::node_interner::NodeInterner;
-use acvm::acir::circuit::Opcode;
 use def_map::CrateDefMap;
 use fm::FileManager;
 use std::collections::HashMap;
@@ -29,20 +28,14 @@ pub struct Context {
 pub type StorageSlot = u32;
 
 impl Context {
-    pub fn new(
-        file_manager: FileManager,
-        crate_graph: CrateGraph,
-        is_opcode_supported: Box<dyn Fn(&Opcode) -> bool>,
-    ) -> Context {
-        let mut ctx = Context {
+    pub fn new(file_manager: FileManager, crate_graph: CrateGraph) -> Context {
+        Context {
             def_interner: NodeInterner::default(),
             def_maps: HashMap::new(),
             crate_graph,
             file_manager,
             storage_slots: HashMap::new(),
-        };
-        ctx.def_interner.set_opcode_support(is_opcode_supported);
-        ctx
+        }
     }
 
     /// Returns the CrateDefMap for a given CrateId.

crates/noirc_frontend/src/hir/resolution/resolver.rs

@@ -1149,23 +1149,7 @@ impl<'a> Resolver<'a> {
         let span = path.span();
         let id = self.resolve_path(path)?;
 
-        if let Some(mut function) = TryFromModuleDefId::try_from(id) {
-            // Check if this is an unsupported low level opcode. If so, replace it with
-            // an alternative in the stdlib.
-            if let Some(meta) = self.interner.try_function_meta(&function) {
-                if meta.kind == crate::FunctionKind::LowLevel {
-                    let attribute = meta.attributes.expect("all low level functions must contain an attribute which contains the opcode which it links to");
-                    let opcode = attribute.foreign().expect(
-                        "ice: function marked as foreign, but attribute kind does not match this",
-                    );
-                    if !self.interner.foreign(&opcode) {
-                        if let Some(new_id) = self.interner.get_alt(opcode) {
-                            function = new_id;
-                        }
-                    }
-                }
-            }
-
+        if let Some(function) = TryFromModuleDefId::try_from(id) {
             return Ok(self.interner.function_definition_id(function));
         }
 

crates/noirc_frontend/src/lexer/token.rs

@@ -324,7 +324,6 @@ impl IntType {
 pub enum Attribute {
     Foreign(String),
     Builtin(String),
-    Alternative(String),
     Test,
 }
 
@@ -333,7 +332,6 @@ impl fmt::Display for Attribute {
         match *self {
             Attribute::Foreign(ref k) => write!(f, "#[foreign({k})]"),
             Attribute::Builtin(ref k) => write!(f, "#[builtin({k})]"),
-            Attribute::Alternative(ref k) => write!(f, "#[alternative({k})]"),
             Attribute::Test => write!(f, "#[test]"),
         }
     }
@@ -365,7 +363,6 @@ impl Attribute {
         let tok = match attribute_type {
             "foreign" => Token::Attribute(Attribute::Foreign(attribute_name.to_string())),
             "builtin" => Token::Attribute(Attribute::Builtin(attribute_name.to_string())),
-            "alternative" => Token::Attribute(Attribute::Alternative(attribute_name.to_string())),
             _ => {
                 return Err(LexerErrorKind::MalformedFuncAttribute { span, found: word.to_owned() })
             }
@@ -401,7 +398,6 @@ impl AsRef<str> for Attribute {
         match self {
             Attribute::Foreign(string) => string,
             Attribute::Builtin(string) => string,
-            Attribute::Alternative(string) => string,
             Attribute::Test => "",
         }
     }

crates/noirc_frontend/src/main.rs

@@ -27,12 +27,7 @@ fn main() {
     let crate_id = crate_graph.add_crate_root(CrateType::Library, root_file_id);
 
     // initiate context with file manager and crate graph
-    let mut context = Context::new(
-        fm,
-        crate_graph,
-        #[allow(deprecated)]
-        Box::new(acvm::default_is_opcode_supported(acvm::Language::R1CS)),
-    );
+    let mut context = Context::new(fm, crate_graph);
 
     // Now create the CrateDefMap
     // This is preamble for analysis

crates/noirc_frontend/src/node_interner.rs

@@ -1,8 +1,5 @@
 use std::collections::{BTreeMap, HashMap};
 
-use acvm::acir::circuit::opcodes::BlackBoxFuncCall;
-use acvm::acir::circuit::Opcode;
-use acvm::Language;
 use arena::{Arena, Index};
 use fm::FileId;
 use iter_extended::vecmap;
@@ -69,9 +66,6 @@ pub struct NodeInterner {
 
     next_type_variable_id: usize,
 
-    //used for fallback mechanism
-    is_opcode_supported: Box<dyn Fn(&Opcode) -> bool>,
-
     delayed_type_checks: Vec<TypeCheckFn>,
 
     /// A map from a struct type and method name to a function id for the method.
@@ -258,8 +252,6 @@ impl Default for NodeInterner {
             field_indices: HashMap::new(),
             next_type_variable_id: 0,
             globals: HashMap::new(),
-            #[allow(deprecated)]
-            is_opcode_supported: Box::new(acvm::default_is_opcode_supported(Language::R1CS)),
             delayed_type_checks: vec![],
             struct_methods: HashMap::new(),
             primitive_methods: HashMap::new(),
@@ -396,17 +388,6 @@ impl NodeInterner {
         self.func_meta.insert(func_id, func_data);
     }
 
-    pub fn get_alt(&self, opcode: String) -> Option<FuncId> {
-        for (func_id, meta) in &self.func_meta {
-            if let Some(crate::token::Attribute::Alternative(name)) = &meta.attributes {
-                if *name == opcode {
-                    return Some(*func_id);
-                }
-            }
-        }
-        None
-    }
-
     pub fn push_definition(
         &mut self,
         name: String,
@@ -580,23 +561,6 @@ impl NodeInterner {
         self.function_definition_ids[&function]
     }
 
-    pub fn set_opcode_support(&mut self, is_opcode_supported: Box<dyn Fn(&Opcode) -> bool>) {
-        self.is_opcode_supported = is_opcode_supported;
-    }
-
-    #[allow(deprecated)]
-    pub fn foreign(&self, opcode: &str) -> bool {
-        let black_box_func = match acvm::acir::BlackBoxFunc::lookup(opcode) {
-            Some(black_box_func) => black_box_func,
-            None => return false,
-        };
-        (self.is_opcode_supported)(&Opcode::BlackBoxFuncCall(BlackBoxFuncCall {
-            name: black_box_func,
-            inputs: Vec::new(),
-            outputs: Vec::new(),
-        }))
-    }
-
     pub fn push_delayed_type_check(&mut self, f: TypeCheckFn) {
         self.delayed_type_checks.push(f);
     }

noir_stdlib/src/merkle.nr

@@ -13,7 +13,6 @@ fn check_membership(_root : Field, _leaf : Field, _index : Field, _hash_path: [F
 fn compute_merkle_root(_leaf : Field, _index : Field, _hash_path: [Field]) -> Field {}
 
 // Returns the root of the tree from the provided leaf and its hashpath, using pedersen hash
-#[alternative(compute_merkle_root)]
 fn compute_root_from_leaf(leaf : Field, index : Field, hash_path: [Field]) -> Field {
     let n = hash_path.len();
     let index_bits = index.to_le_bits(n as u32);

noir_stdlib/src/sha256.nr

@@ -99,7 +99,6 @@ fn msg_u8_to_u32(msg: [u8; 64]) -> [u32; 16]
 }
 
 // SHA-256 hash function
-#[alternative(sha256)]
 fn digest<N>(msg: [u8; N]) -> [u8; 32] {
     let mut msg_block: [u8; 64] = [0; 64];
     let mut h: [u32; 8] = [1779033703,3144134277,1013904242,2773480762,1359893119,2600822924,528734635,1541459225]; // Intermediate hash, starting with the canonical initial value