chore: lldb bb debugging helper script (#7627)

Pretty-print tricky to debug field types

barretenberg/README.md

@@ -349,3 +349,15 @@ Stack trace (most recent call last):
          25:     blocks.arithmetic.q_2().emplace_back(in.b_scaling);
 gate number4
 ```
+
+
+### Improving LLDB Debugging
+
+It can be quite hard to make sense of field_t circuit values that indirectly reference their contents, and even plain field values that are typically in montgomery form.
+In command-line LLDB or VSCode debug console, run:
+
+```
+command script import ~/aztec-packages/barretenberg/cpp/scripts/lldb_format.py
+```
+
+Now when you `print` things with e.g. `print bigfield_t.get_value()` or inspect in VSCode (if you opened the debug console and put in these commands) then you will get pretty-printing of these types. This can be expanded fairly easily with more types if needed.

barretenberg/cpp/scripts/lldb_format.py

@@ -0,0 +1,45 @@
+import lldb
+
+# Define the bn254 modulus
+N = 21888242871839275222246405745257275088548364400416034343698204186575808495617
+
+# Define R as a power of 2 such that R > N (commonly used R for bn254 is 2^256)
+R = 2**256
+
+# Compute R inverse modulo N
+R_inv = pow(R, -1, N)
+
+def montgomery_to_standard(montgomery_value):
+    # Convert from Montgomery form to standard representation
+    standard_value = (montgomery_value * R_inv) % N
+    return standard_value
+
+def montgomery_summary(valobj, internal_dict):
+    try:
+        data = valobj.GetChildMemberWithName('data')
+        data_0 = data.GetChildAtIndex(0).GetValueAsUnsigned()
+        data_1 = data.GetChildAtIndex(1).GetValueAsUnsigned()
+        data_2 = data.GetChildAtIndex(2).GetValueAsUnsigned()
+        data_3 = data.GetChildAtIndex(3).GetValueAsUnsigned()
+
+        montgomery_value = (
+            data_0 +
+            (data_1 << 64) +
+            (data_2 << 128) +
+            (data_3 << 192)
+        )
+
+        standard_value = montgomery_to_standard(montgomery_value)
+        return hex(standard_value)
+    except Exception as e:
+        return f"Error: {e}"
+
+
+def montgomery_summary2(valobj, internal_dict):
+    return montgomery_summary(valobj.EvaluateExpression("get_value()"), internal_dict)
+
+
+def __lldb_init_module(debugger, internal_dict):
+    debugger.HandleCommand("type summary add --python-function lldb_format.montgomery_summary bb::fr")
+    debugger.HandleCommand("type summary add --python-function lldb_format.montgomery_summary2 -x \"bb::stdlib::field_t.*\"")
+    print('The "formatter" command has been installed!')