Merge d63d059 into 824d76f

noir/.gitrepo

@@ -6,7 +6,7 @@
 [subrepo]
 	remote = https://github.com/noir-lang/noir
 	branch = aztec-packages
-	commit = 7f22446f3940f8ef7ccae785a4b29835f2e869fe
-	parent = fd1f619f443916c172b6311aa71a84153145ef4d
+	commit = 0f38b229f5ed6024e5a0ffe8fd502264b282d3aa
+	parent = e28a6bf14cee1f7bade14337c74ecdcba1350899
 	method = merge
 	cmdver = 0.4.6

noir/compiler/noirc_driver/tests/stdlib_warnings.rs

@@ -0,0 +1,27 @@
+use std::path::Path;
+
+use noirc_driver::{file_manager_with_stdlib, prepare_crate, ErrorsAndWarnings};
+use noirc_frontend::hir::Context;
+
+#[test]
+fn stdlib_does_not_produce_constant_warnings() -> Result<(), ErrorsAndWarnings> {
+    // We use a minimal source file so that if stdlib produces warnings then we can expect these warnings to _always_
+    // be emitted.
+    let source = "fn main() {}";
+
+    let root = Path::new("");
+    let file_name = Path::new("main.nr");
+    let mut file_manager = file_manager_with_stdlib(root);
+    file_manager.add_file_with_source(file_name, source.to_owned()).expect(
+        "Adding source buffer to file manager should never fail when file manager is empty",
+    );
+
+    let mut context = Context::new(file_manager);
+    let root_crate_id = prepare_crate(&mut context, file_name);
+
+    let ((), warnings) = noirc_driver::check_crate(&mut context, root_crate_id, false, false)?;
+
+    assert_eq!(warnings, Vec::new(), "stdlib is producing warnings");
+
+    Ok(())
+}

noir/compiler/noirc_evaluator/src/ssa/function_builder/mod.rs

@@ -293,8 +293,9 @@ impl FunctionBuilder {
             if let Some(rhs_constant) = self.current_function.dfg.get_numeric_constant(rhs) {
                 // Happy case is that we know precisely by how many bits the the integer will
                 // increase: lhs_bit_size + rhs
-                let (rhs_bit_size_pow_2, overflows) =
-                    2_u128.overflowing_pow(rhs_constant.to_u128() as u32);
+                let bit_shift_size = rhs_constant.to_u128() as u32;
+
+                let (rhs_bit_size_pow_2, overflows) = 2_u128.overflowing_pow(bit_shift_size);
                 if overflows {
                     assert!(bit_size < 128, "ICE - shift left with big integers are not supported");
                     if bit_size < 128 {
@@ -303,7 +304,10 @@ impl FunctionBuilder {
                     }
                 }
                 let pow = self.numeric_constant(FieldElement::from(rhs_bit_size_pow_2), typ);
-                (bit_size + (rhs_constant.to_u128() as u32), pow)
+
+                let max_lhs_bits = self.current_function.dfg.get_value_max_num_bits(lhs);
+
+                (max_lhs_bits + bit_shift_size, pow)
             } else {
                 // we use a predicate to nullify the result in case of overflow
                 let bit_size_var =

noir/compiler/noirc_evaluator/src/ssa/ir/dfg.rs

@@ -337,6 +337,25 @@ impl DataFlowGraph {
         self.values[value].get_type().clone()
     }
 
+    /// Returns the maximum possible number of bits that `value` can potentially be.
+    ///
+    /// Should `value` be a numeric constant then this function will return the exact number of bits required,
+    /// otherwise it will return the minimum number of bits based on type information.
+    pub(crate) fn get_value_max_num_bits(&self, value: ValueId) -> u32 {
+        match self[value] {
+            Value::Instruction { instruction, .. } => {
+                if let Instruction::Cast(original_value, _) = self[instruction] {
+                    self.type_of_value(original_value).bit_size()
+                } else {
+                    self.type_of_value(value).bit_size()
+                }
+            }
+
+            Value::NumericConstant { constant, .. } => constant.num_bits(),
+            _ => self.type_of_value(value).bit_size(),
+        }
+    }
+
     /// True if the type of this value is Type::Reference.
     /// Using this method over type_of_value avoids cloning the value's type.
     pub(crate) fn value_is_reference(&self, value: ValueId) -> bool {

noir/compiler/noirc_evaluator/src/ssa/ssa_gen/context.rs

@@ -335,29 +335,71 @@ impl<'a> FunctionContext<'a> {
                 }
             }
             Type::Numeric(NumericType::Unsigned { bit_size }) => {
-                let op_name = match operator {
-                    BinaryOpKind::Add => "add",
-                    BinaryOpKind::Subtract => "subtract",
-                    BinaryOpKind::Multiply => "multiply",
-                    BinaryOpKind::ShiftLeft => "left shift",
-                    _ => unreachable!("operator {} should not overflow", operator),
-                };
+                let dfg = &self.builder.current_function.dfg;
 
-                if operator == BinaryOpKind::Multiply && bit_size == 1 {
-                    result
-                } else if operator == BinaryOpKind::ShiftLeft
-                    || operator == BinaryOpKind::ShiftRight
-                {
-                    self.check_shift_overflow(result, rhs, bit_size, location, false)
-                } else {
-                    let message = format!("attempt to {} with overflow", op_name);
-                    self.builder.set_location(location).insert_range_check(
-                        result,
-                        bit_size,
-                        Some(message),
-                    );
-                    result
+                let max_lhs_bits = self.builder.current_function.dfg.get_value_max_num_bits(lhs);
+                let max_rhs_bits = self.builder.current_function.dfg.get_value_max_num_bits(rhs);
+
+                match operator {
+                    BinaryOpKind::Add => {
+                        if std::cmp::max(max_lhs_bits, max_rhs_bits) < bit_size {
+                            // `lhs` and `rhs` have both been casted up from smaller types and so cannot overflow.
+                            return result;
+                        }
+
+                        let message = "attempt to add with overflow".to_string();
+                        self.builder.set_location(location).insert_range_check(
+                            result,
+                            bit_size,
+                            Some(message),
+                        );
+                    }
+                    BinaryOpKind::Subtract => {
+                        if dfg.is_constant(lhs) && max_lhs_bits > max_rhs_bits {
+                            // `lhs` is a fixed constant and `rhs` is restricted such that `lhs - rhs > 0`
+                            // Note strict inequality as `rhs > lhs` while `max_lhs_bits == max_rhs_bits` is possible.
+                            return result;
+                        }
+
+                        let message = "attempt to subtract with overflow".to_string();
+                        self.builder.set_location(location).insert_range_check(
+                            result,
+                            bit_size,
+                            Some(message),
+                        );
+                    }
+                    BinaryOpKind::Multiply => {
+                        if bit_size == 1 || max_lhs_bits + max_rhs_bits <= bit_size {
+                            // Either performing boolean multiplication (which cannot overflow),
+                            // or `lhs` and `rhs` have both been casted up from smaller types and so cannot overflow.
+                            return result;
+                        }
+
+                        let message = "attempt to multiply with overflow".to_string();
+                        self.builder.set_location(location).insert_range_check(
+                            result,
+                            bit_size,
+                            Some(message),
+                        );
+                    }
+                    BinaryOpKind::ShiftLeft => {
+                        if let Some(rhs_const) = dfg.get_numeric_constant(rhs) {
+                            let bit_shift_size = rhs_const.to_u128() as u32;
+
+                            if max_lhs_bits + bit_shift_size <= bit_size {
+                                // `lhs` has been casted up from a smaller type such that shifting it by a constant
+                                // `rhs` is known not to exceed the maximum bit size.
+                                return result;
+                            }
+                        }
+
+                        self.check_shift_overflow(result, rhs, bit_size, location, false);
+                    }
+
+                    _ => unreachable!("operator {} should not overflow", operator),
                 }
+
+                result
             }
             _ => result,
         }