Move usse-decoder-gen to tools

(cherry picked from commit 6f00696a578888dfc7a716c82786b3515490a8ad)
(cherry picked from commit 972cee8e9d75162c26f7d2fd8e81a3975d4e18e4)

tools/usse-decoder-gen/autogen.py

@@ -0,0 +1,122 @@
+import yaml
+import string
+import sys
+
+
+# Need Python 3.6 or newer for stable insertion order dicts
+assert sys.version_info >= (3, 6), 'Needs Python 3.6 or newer'
+
+# Set this to true to indent the annotation string in line with the match string
+STAIRCASE_INDENT = True
+
+
+def allocate_char(chars_used, name):
+    # Pick a character from the identifier
+    for c in name:
+        if c not in chars_used and c in string.ascii_letters:
+            return c
+
+    # Fallback to the first free alphabetic character
+    c = 'a'
+    while c in chars_used:
+        if c == 'z':
+            c = 'A'
+        else:
+            c = chr(ord(c) + 1)
+    return c
+
+
+funcdefs = []
+matchers = []
+
+d = yaml.load(open('grammar.yaml'))
+
+for k, v in d.items():
+    members = []
+    description = v.get('description', '')
+    offset = 64
+    for member in v['members']:
+        for mk, mv in member.items():
+            if isinstance(mv, str):
+                # Literal binary match
+                mv = {'size': len(mv), 'match': mv}
+            elif isinstance(mv, int):
+                # Simple bit field
+                mv = {'size': mv}
+
+            if 'type' not in mv:
+                mv['type'] = f'Imm{mv["size"]}'
+
+            if 'offset' in mv:
+                # Re-adjust offset and potentially insert DONTCARE bits
+                new_offset = mv['offset'] + mv['size']
+                assert new_offset <= offset, f'Offset {new_offset} must be less or equal to current offset {offset}'
+                dontcare_bits = offset - new_offset
+                if dontcare_bits != 0:
+                    members.append(
+                        ('DONTCARE', 64-offset, {'size': dontcare_bits, 'type': f'Imm{dontcare_bits}'}))
+                    offset = new_offset
+
+            members.append((mk, 64-offset, mv))
+            offset -= mv['size']
+
+    # Insert DONTCARE bits at the end (if any)
+    if offset > 0:
+        dontcare_bits = offset
+        members.append(
+            ('DONTCARE', 64-offset, {'size': dontcare_bits, 'type': f'Imm{dontcare_bits}'}))
+        offset = 0
+
+    assert offset == 0, f'Definition of {k} does not fit in 64 bits'
+
+    v["handler"] = k.lower()
+    args = ',\n    '.join(f'{props["type"]} {name}' for name,
+                          offset, props in members if name != 'DONTCARE' and 'match' not in props)
+    func = f'bool USSETranslatorVisitor::{v["handler"]}(\n    {args})\n{{\n}}'
+    funcdefs.append(func)
+
+    # Create match string and assign bit characters
+    matchstr = ''
+    annotations = []
+    chars_used = {}
+    PREFIX = f'INST(&V::{v["handler"]}, "{k} ()", "'
+    SUFFIX = '"),'
+    indent = len(PREFIX)
+    for name, offset, props in members:
+        indentation = ' ' * (indent + offset) if STAIRCASE_INDENT else '  '
+        size = props['size']
+        if name == 'DONTCARE':
+            matchstr += '-' * size
+            annotations.append(f'{indentation}{"-"*size} = don\'t care')
+        elif 'match' in props:
+            # Literal bit pattern match
+            matchstr += props['match']
+            annotations.append(f'{indentation}{props["match"]} = {name}')
+        else:
+            char = allocate_char(chars_used, name)
+            chars_used[char] = name
+            matchstr += char * size
+            bitinfo = '1 bit' if size == 1 else f'{size} bits'
+            arginfo = '' if props['type'].startswith(
+                'Imm') else f', {props["type"]}'
+            annotations.append(
+                f'{indentation}{char*size} = {name} ({bitinfo}{arginfo})')
+
+    annotation = '\n'.join(annotations)
+    matchers.append(f'// {description}\n/*\n{annotation}\n*/\n{PREFIX}{matchstr}{SUFFIX}')
+
+
+def dump(fp):
+    print('// Functions\n', file=fp)
+    for funcdef in funcdefs:
+        print(funcdef, file=fp)
+        print('', file=fp)
+
+    print('\n\n// Matchers\n', file=fp)
+    for matcher in matchers:
+        print(matcher, file=fp)
+        print('', file=fp)
+
+
+dump(sys.stdout)
+dump(open('autogen_out.cpp', 'w'))