feat: Implement poseidon2_permutation in comptime interpreter

compiler/noirc_frontend/Cargo.toml

@@ -10,6 +10,7 @@ license.workspace = true
 
 [dependencies]
 acvm.workspace = true
+bn254_blackbox_solver.workspace = true
 noirc_arena.workspace = true
 noirc_errors.workspace = true
 noirc_printable_type.workspace = true

compiler/noirc_frontend/src/hir/comptime/errors.rs

@@ -7,7 +7,7 @@
     token::Tokens,
     Type,
 };
-use acvm::{acir::AcirField, FieldElement};
+use acvm::{acir::AcirField, BlackBoxResolutionError, FieldElement};
 use fm::FileId;
 use iter_extended::vecmap;
 use noirc_errors::{CustomDiagnostic, Location};
@@ -53,13 +53,11 @@
     NoImpl { location: Location },
     NoMatchingImplFound { error: NoMatchingImplFoundError, file: FileId },
     ImplMethodTypeMismatch { expected: Type, actual: Type, location: Location },
-
-    Unimplemented { item: String, location: Location },
-
-    // Perhaps this should be unreachable! due to type checking also preventing this error?
-    // Currently it and the Continue variant are the only interpreter errors without a Location field
     BreakNotInLoop { location: Location },
     ContinueNotInLoop { location: Location },
+    BlackBoxError(BlackBoxResolutionError, Location),
+
+    Unimplemented { item: String, location: Location },
 
     // These cases are not errors, they are just used to prevent us from running more code
     // until the loop can be resumed properly. These cases will never be displayed to users.
@@ -118,9 +116,11 @@
             | InterpreterError::Unimplemented { location, .. }
             | InterpreterError::NoImpl { location, .. }
             | InterpreterError::ImplMethodTypeMismatch { location, .. }
+            | InterpreterError::DebugEvaluateComptime { location, .. }
+            | InterpreterError::BlackBoxError(_, location)
             | InterpreterError::BreakNotInLoop { location, .. }
-            | InterpreterError::DebugEvaluateComptime { location, .. } => *location,
-            InterpreterError::ContinueNotInLoop { location, .. } => *location,
+            | InterpreterError::ContinueNotInLoop { location, .. } => *location,
+
             InterpreterError::FailedToParseMacro { error, file, .. } => {
                 Location::new(error.span(), *file)
             }
@@ -313,7 +313,7 @@
                 let message = format!("Failed to parse macro's token stream into {rule}");
                 let tokens = vecmap(&tokens.0, ToString::to_string).join(" ");
 
                 // 10 is an aribtrary number of tokens here chosen to fit roughly onto one line
                 let token_stream = if tokens.len() > 10 {
                     format!("The resulting token stream was: {tokens}")
                 } else {
@@ -370,6 +370,9 @@
                 );
                 CustomDiagnostic::simple_error(msg, String::new(), location.span)
             }
+            InterpreterError::BlackBoxError(error, location) => {
+                CustomDiagnostic::simple_error(error.to_string(), String::new(), location.span)
+            }
             InterpreterError::NoMatchingImplFound { error, .. } => error.into(),
             InterpreterError::Break => unreachable!("Uncaught InterpreterError::Break"),
             InterpreterError::Continue => unreachable!("Uncaught InterpreterError::Continue"),

compiler/noirc_frontend/src/hir/comptime/interpreter.rs

@@ -38,6 +38,7 @@
 use super::value::{unwrap_rc, Value};
 
 mod builtin;
+mod foreign;
 mod unquote;
 
 #[allow(unused)]
@@ -144,8 +145,8 @@
             let builtin = builtin.clone();
             builtin::call_builtin(self.elaborator.interner, &builtin, arguments, location)
         } else if let Some(foreign) = func_attrs.foreign() {
-            let item = format!("Comptime evaluation for foreign functions like {foreign}");
-            Err(InterpreterError::Unimplemented { item, location })
+            let foreign = foreign.clone();
+            foreign::call_foreign(self.elaborator.interner, &foreign, arguments, location)
         } else if let Some(oracle) = func_attrs.oracle() {
             if oracle == "print" {
                 self.print_oracle(arguments)
@@ -163,7 +164,7 @@
         &mut self,
         closure: HirLambda,
         // TODO: How to define environment here?
         _environment: Vec<Value>,
         arguments: Vec<(Value, Location)>,
         call_location: Location,
     ) -> IResult<Value> {

compiler/noirc_frontend/src/hir/comptime/interpreter/builtin.rs

@@ -55,7 +55,7 @@ pub(super) fn call_builtin(
     }
 }
 
-fn check_argument_count(
+pub(super) fn check_argument_count(
     expected: usize,
     arguments: &[(Value, Location)],
     location: Location,
@@ -73,6 +73,21 @@ fn failing_constraint<T>(message: impl Into<String>, location: Location) -> IRes
     Err(InterpreterError::FailingConstraint { message, location })
 }
 
+pub(super) fn get_array(
+    interner: &NodeInterner,
+    value: Value,
+    location: Location,
+) -> IResult<(im::Vector<Value>, Type)> {
+    match value {
+        Value::Array(values, typ) => Ok((values, typ)),
+        value => {
+            let type_var = Box::new(interner.next_type_variable());
+            let expected = Type::Array(type_var.clone(), type_var);
+            Err(InterpreterError::TypeMismatch { expected, value, location })
+        }
+    }
+}
+
 fn get_slice(
     interner: &NodeInterner,
     value: Value,
@@ -88,7 +103,16 @@ fn get_slice(
     }
 }
 
-fn get_u32(value: Value, location: Location) -> IResult<u32> {
+pub(super) fn get_field(value: Value, location: Location) -> IResult<FieldElement> {
+    match value {
+        Value::Field(value) => Ok(value),
+        value => {
+            Err(InterpreterError::TypeMismatch { expected: Type::FieldElement, value, location })
+        }
+    }
+}
+
+pub(super) fn get_u32(value: Value, location: Location) -> IResult<u32> {
     match value {
         Value::U32(value) => Ok(value),
         value => {

compiler/noirc_frontend/src/hir/comptime/interpreter/foreign.rs

@@ -0,0 +1,48 @@
+use acvm::BlackBoxFunctionSolver;
+use bn254_blackbox_solver::Bn254BlackBoxSolver;
+use iter_extended::try_vecmap;
+use noirc_errors::Location;
+
+use crate::{
+    hir::comptime::{errors::IResult, interpreter::builtin::get_field, InterpreterError, Value},
+    macros_api::NodeInterner,
+};
+
+use super::builtin::{check_argument_count, get_array, get_u32};
+
+pub(super) fn call_foreign(
+    interner: &mut NodeInterner,
+    name: &str,
+    arguments: Vec<(Value, Location)>,
+    location: Location,
+) -> IResult<Value> {
+    match name {
+        "poseidon2_permutation" => poseidon2_permutation(interner, arguments, location),
+        _ => {
+            let item = format!("Comptime evaluation for builtin function {name}");
+            Err(InterpreterError::Unimplemented { item, location })
+        }
+    }
+}
+
+// poseidon2_permutation<let N: u32>(_input: [Field; N], _state_length: u32) -> [Field; N]
+fn poseidon2_permutation(
+    interner: &mut NodeInterner,
+    mut arguments: Vec<(Value, Location)>,
+    location: Location,
+) -> IResult<Value> {
+    check_argument_count(2, &arguments, location)?;
+
+    let state_length = get_u32(arguments.pop().unwrap().0, location)?;
+    let (input, typ) = get_array(interner, arguments.pop().unwrap().0, location)?;
+
+    let input = try_vecmap(input, |integer| get_field(integer, location))?;
+
+    // Currently locked to only bn254!
+    let fields = Bn254BlackBoxSolver
+        .poseidon2_permutation(&input, state_length)
+        .map_err(|error| InterpreterError::BlackBoxError(error, location))?;
+
+    let array = fields.into_iter().map(Value::Field).collect();
+    Ok(Value::Array(array, typ))
+}