C++: Sync Opcode.qll QLDoc with Instruction.qll QLDoc

For every concrete `Opcode`, there is a corresponding `Instruction` class. Rather than duplicate all of the QLDoc by hand, I wrote a quick Python script to copy the QLDoc from `Instruction.qll` to `Opcode.qll`. I don't expect that we will need to do this often, so I'm not hooking it up to a PR check or anything like that, but I did commit the script itself in case we need it again.

config/opcode-qldoc.py

@@ -0,0 +1,83 @@
+#!/usr/bin/env python3
+
+import os
+import re
+path = os.path
+
+start_qldoc_re = re.compile(r'^\s*/\*\*')  # Start of a QLDoc comment
+end_qldoc_re = re.compile(r'\*/\s*$')  # End of a QLDoc comment
+blank_qldoc_line_re = re.compile(r'^\s*\*\s*$')  # A line in a QLDoc comment with only the '*'
+instruction_class_re = re.compile(r'^class (?P<name>[A-aa-z0-9]+)Instruction\s')  # Declaration of an `Instruction` class
+opcode_class_re = re.compile(r'^\s*class (?P<name>[A-aa-z0-9]+)\s')  # Declaration of an `Opcode` class
+
+script_dir = path.realpath(path.dirname(__file__))
+instruction_path = path.realpath(path.join(script_dir, '../cpp/ql/src/semmle/code/cpp/ir/implementation/raw/Instruction.qll'))
+opcode_path = path.realpath(path.join(script_dir, '../cpp/ql/src/semmle/code/cpp/ir/implementation/Opcode.qll'))
+
+# Scan `Instruction.qll`, keeping track of the QLDoc comment attached to each declaration of a class
+# whose name ends with `Instruction`.
+instruction_comments = {}
+in_qldoc = False
+saw_blank_line_in_qldoc = False
+qldoc_lines = []
+with open(instruction_path, 'r', encoding='utf-8') as instr:
+    for line in instr:
+        if in_qldoc:
+            if end_qldoc_re.search(line):
+                qldoc_lines.append(line)
+                in_qldoc = False
+            elif blank_qldoc_line_re.search(line):
+                # We're going to skip any lines after the first blank line, to avoid duplicating all
+                # of the verbose description.
+                saw_blank_line_in_qldoc = True
+            elif not saw_blank_line_in_qldoc:
+                qldoc_lines.append(line)
+        else:
+            if start_qldoc_re.search(line):
+                # Starting a new QLDoc comment.
+                saw_blank_line_in_qldoc = False
+                qldoc_lines.append(line)
+                if not end_qldoc_re.search(line):
+                    in_qldoc = True
+            else:
+                instruction_match = instruction_class_re.search(line)
+                if instruction_match:
+                    # Found the declaration of an `Instruction` class. Record the QLDoc comments.
+                    instruction_comments[instruction_match.group('name')] = qldoc_lines
+                qldoc_lines = []
+
+# Scan `Opcode.qll`. Whenever we see the declaration of an `Opcode` class for which we have a
+# corresponding `Instruction` class, we'll attach a copy of the `Instruction`'s QLDoc comment.
+in_qldoc = False
+qldoc_lines = []
+output_lines = []
+with open(opcode_path, 'r', encoding='utf-8') as opcode:
+    for line in opcode:
+        if in_qldoc:
+            qldoc_lines.append(line)
+            if end_qldoc_re.search(line):
+                in_qldoc = False
+        else:
+            if start_qldoc_re.search(line):
+                qldoc_lines.append(line)
+                if not end_qldoc_re.search(line):
+                    in_qldoc = True
+            else:
+                opcode_match = opcode_class_re.search(line)
+                if opcode_match:
+                    # Found an `Opcode` that matches a known `Instruction`. Replace the QLDoc with
+                    # a copy of the one from the `Instruction`.
+                    name = opcode_match.group('name')
+                    if instruction_comments.get(name):
+                        # Indent by two additional spaces, since opcodes are declared in the
+                        # `Opcode` module.
+                        # Rename `instruction` to `operation`.
+                        qldoc_lines = [('  ' + qldoc_line.replace(' An instruction ', ' An operation '))
+                            for qldoc_line in instruction_comments[name]]
+                output_lines.extend(qldoc_lines)
+                qldoc_lines = []
+                output_lines.append(line)
+
+# Write out the updated `Opcode.qll`
+with open(opcode_path, 'w', encoding='utf-8') as opcode:
+    opcode.writelines(output_lines)