fix: do not simplify call-data values

compiler/noirc_evaluator/src/acir/acir_context/mod.rs

@@ -133,6 +133,13 @@ impl<F: AcirField> AcirContext<F> {
             return Ok(());
         }
 
+        if let Some(w) = self.var_to_expression(lhs)?.to_witness() {
+            if self.acir_ir.input_witnesses.contains(&w) {
+                //Input witnesses are not replaced
+                return Ok(());
+            }
+        }
+
         let lhs_data = self.vars.remove(&lhs).ok_or_else(|| InternalError::UndeclaredAcirVar {
             call_stack: self.get_call_stack(),
         })?;
@@ -1321,11 +1328,9 @@ impl<F: AcirField> AcirContext<F> {
     /// Terminates the context and takes the resulting `GeneratedAcir`
     pub(crate) fn finish(
         mut self,
-        inputs: Vec<Witness>,
         return_values: Vec<Witness>,
         warnings: Vec<SsaReport>,
     ) -> GeneratedAcir<F> {
-        self.acir_ir.input_witnesses = inputs;
         self.acir_ir.return_witnesses = return_values;
         self.acir_ir.warnings = warnings;
         self.acir_ir

compiler/noirc_evaluator/src/acir/mod.rs

@@ -176,7 +176,9 @@ impl<'a> Context<'a> {
     ) -> Result<GeneratedAcir<FieldElement>, RuntimeError> {
         let dfg = &main_func.dfg;
         let entry_block = &dfg[main_func.entry_block()];
-        let input_witness = self.convert_ssa_block_params(entry_block.parameters(), dfg)?;
+        self.acir_context.acir_ir.input_witnesses =
+            self.convert_ssa_block_params(entry_block.parameters(), dfg)?;
+
         let num_return_witnesses =
             self.get_num_return_witnesses(entry_block.unwrap_terminator(), dfg);
 
@@ -250,7 +252,6 @@ impl<'a> Context<'a> {
 
         // Add the warnings from the alter Ssa passes
         Ok(self.acir_context.finish(
-            input_witness,
             // Don't embed databus return witnesses into the circuit.
             if self.data_bus.return_data.is_some() { Vec::new() } else { return_witnesses },
             warnings,
@@ -269,7 +270,7 @@ impl<'a> Context<'a> {
         })?;
         let arguments = self.gen_brillig_parameters(dfg[main_func.entry_block()].parameters(), dfg);
 
-        let witness_inputs = self.acir_context.extract_witness(&inputs);
+        self.acir_context.acir_ir.input_witnesses = self.acir_context.extract_witness(&inputs);
         let returns = main_func.returns().unwrap_or_default();
 
         let outputs: Vec<AcirType> =
@@ -303,7 +304,7 @@ impl<'a> Context<'a> {
             .map(|(value, _)| self.acir_context.var_to_witness(value))
             .collect::<Result<_, _>>()?;
 
-        let generated_acir = self.acir_context.finish(witness_inputs, return_witnesses, Vec::new());
+        let generated_acir = self.acir_context.finish(return_witnesses, Vec::new());
 
         assert_eq!(
             generated_acir.opcodes().len(),

compiler/noirc_evaluator/src/acir/tests/mod.rs

@@ -296,6 +296,34 @@ fn derive_pedersen_generators_requires_constant_input() {
         .expect_err("Should fail with assert constant");
 }
 
+#[test]
+fn databus() {
+    let src = "
+    acir(inline) predicate_pure fn main f0 {
+        b0(v0: u32, v1: u32):
+            v2 = cast v0 as Field
+            v3 = make_array [v2] : [Field; 1]
+            constrain v0 == u32 0
+            v4 = add v0, v1
+            return v4
+        }
+    ";
+    let program = ssa_to_acir_program(src);
+
+    // Check that w0 is not replaced
+    assert_circuit_snapshot!(program, @r"
+        func 0
+        private parameters: [w0, w1]
+        public parameters: []
+        return values: [w2]
+        BLACKBOX::RANGE input: w1, bits: 32
+        ASSERT w0 = 0
+        ASSERT w3 = w0 + w1
+        BLACKBOX::RANGE input: w3, bits: 32
+        ASSERT w3 = w2
+    ");
+}
+
 /// Convert the SSA input into ACIR and use ACVM to execute it
 /// Returns the ACVM execution status and the value of the 'output' witness value,
 /// unless the provided output is None or the ACVM fails during execution.