feat(comptime): Implement to_be_bits and to_le_bits in the interpreter (

#7008)

Co-authored-by: jfecher <[email protected]>

compiler/noirc_evaluator/src/acir/mod.rs

@@ -2169,7 +2169,7 @@ impl<'a> Context<'a> {
 
                 let Type::Array(result_type, array_length) = dfg.type_of_value(result_ids[0])
                 else {
-                    unreachable!("ICE: ToRadix result must be an array");
+                    unreachable!("ICE: ToBits result must be an array");
                 };
 
                 self.acir_context

compiler/noirc_frontend/src/elaborator/types.rs

@@ -1526,7 +1526,7 @@ impl<'context> Elaborator<'context> {
     ) -> Option<HirMethodReference> {
         let func_id = match self.current_item {
             Some(DependencyId::Function(id)) => id,
-            _ => panic!("unexpected method outside a function"),
+            _ => panic!("unexpected method outside a function: {method_name}"),
         };
         let func_meta = self.interner.function_meta(&func_id);
 

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

@@ -192,6 +192,8 @@ impl<'local, 'context> Interpreter<'local, 'context> {
             "struct_def_set_fields" => struct_def_set_fields(interner, arguments, location),
             "to_be_radix" => to_be_radix(arguments, return_type, location),
             "to_le_radix" => to_le_radix(arguments, return_type, location),
+            "to_be_bits" => to_be_bits(arguments, return_type, location),
+            "to_le_bits" => to_le_bits(arguments, return_type, location),
             "trait_constraint_eq" => trait_constraint_eq(arguments, location),
             "trait_constraint_hash" => trait_constraint_hash(arguments, location),
             "trait_def_as_trait_constraint" => {
@@ -776,6 +778,26 @@ fn quoted_tokens(arguments: Vec<(Value, Location)>, location: Location) -> IResu
     ))
 }
 
+fn to_be_bits(
+    arguments: Vec<(Value, Location)>,
+    return_type: Type,
+    location: Location,
+) -> IResult<Value> {
+    let value = check_one_argument(arguments, location)?;
+    let radix = (Value::U32(2), value.1);
+    to_be_radix(vec![value, radix], return_type, location)
+}
+
+fn to_le_bits(
+    arguments: Vec<(Value, Location)>,
+    return_type: Type,
+    location: Location,
+) -> IResult<Value> {
+    let value = check_one_argument(arguments, location)?;
+    let radix = (Value::U32(2), value.1);
+    to_le_radix(vec![value, radix], return_type, location)
+}
+
 fn to_be_radix(
     arguments: Vec<(Value, Location)>,
     return_type: Type,

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

@@ -19,6 +19,8 @@ use crate::node_interner::FuncId;
 use crate::parse_program;
 
 /// Create an interpreter for a code snippet and pass it to a test function.
+///
+/// The stdlib is not made available as a dependency.
 pub(crate) fn with_interpreter<T>(
     src: &str,
     f: impl FnOnce(&mut Interpreter, FuncId, &[(CompilationError, FileId)]) -> T,

compiler/noirc_frontend/src/tests.rs

@@ -65,6 +65,9 @@ pub(crate) fn get_program(src: &str) -> (ParsedModule, Context, Vec<(Compilation
     )
 }
 
+/// Compile a program.
+///
+/// The stdlib is not available for these snippets.
 pub(crate) fn get_program_with_maybe_parser_errors(
     src: &str,
     allow_parser_errors: bool,
@@ -3894,10 +3897,10 @@ fn errors_on_cyclic_globals() {
 #[test]
 fn warns_on_unneeded_unsafe() {
     let src = r#"
-    fn main() { 
+    fn main() {
         /// Safety: test
         unsafe {
-            foo() 
+            foo()
         }
     }
 
@@ -3914,12 +3917,12 @@ fn warns_on_unneeded_unsafe() {
 #[test]
 fn warns_on_nested_unsafe() {
     let src = r#"
-    fn main() { 
+    fn main() {
         /// Safety: test
-        unsafe { 
+        unsafe {
             /// Safety: test
             unsafe {
-                foo() 
+                foo()
             }
         }
     }

test_programs/noir_test_success/global_eval/Nargo.toml

@@ -0,0 +1,7 @@
+[package]
+name = "global_eval"
+type = "bin"
+authors = [""]
+compiler_version = ">=0.27.0"
+
+[dependencies]

test_programs/noir_test_success/global_eval/src/main.nr

@@ -0,0 +1,20 @@
+use std::uint128::U128;
+
+// These definitions require `to_be_bits` and `to_le_bits` to be supported at comptime.
+global BITS_BE_13: [u1; 4] = (13 as Field).to_be_bits();
+global BITS_LE_13: [u1; 4] = (13 as Field).to_le_bits();
+
+// Examples from #6691 which use the above behind the scenes.
+global POW64_A: Field = 2.pow_32(64);
+global POW64_B: Field = (U128::one() << 64).to_integer();
+
+#[test]
+fn test_be_and_le_bits() {
+    assert_eq(BITS_BE_13, [1,1,0,1]);
+    assert_eq(BITS_LE_13, [1,0,1,1]);
+}
+
+#[test]
+fn test_pow64() {
+    assert_eq(POW64_A, POW64_B);
+}