fix: do not remove memory blocks used as brillig input (#7073)

acvm-repo/acvm/src/compiler/optimizers/unused_memory.rs

@@ -1,4 +1,4 @@
-use acir::circuit::{opcodes::BlockId, Circuit, Opcode};
+use acir::circuit::{brillig::BrilligInputs, opcodes::BlockId, Circuit, Opcode};
 use std::collections::HashSet;
 
 /// `UnusedMemoryOptimizer` will remove initializations of memory blocks which are unused.
@@ -29,6 +29,13 @@ impl<F> UnusedMemoryOptimizer<F> {
                 Opcode::MemoryOp { block_id, .. } => {
                     unused_memory_initialization.remove(block_id);
                 }
+                Opcode::BrilligCall { inputs, .. } => {
+                    for input in inputs {
+                        if let BrilligInputs::MemoryArray(block) = input {
+                            unused_memory_initialization.remove(block);
+                        }
+                    }
+                }
                 _ => (),
             }
         }

test_programs/compile_success_no_bug/regression_7062/Nargo.toml

@@ -0,0 +1,7 @@
+[package]
+name = "regression_7062"
+type = "bin"
+authors = [""]
+compiler_version = ">=0.31.0"
+
+[dependencies]

test_programs/compile_success_no_bug/regression_7062/src/main.nr

@@ -0,0 +1,8 @@
+fn main(args: [Field; 2]) {
+    /// Safety: n/a
+    unsafe { store(args) };
+    // Dummy test to remove the 'underconstraint bug'
+    assert(args[0] + args[1] != 0);
+}
+
+pub unconstrained fn store(_: [Field]) {}