[llvm] update_test_checks: keep meta variables stable by default (PR #76748)

[Jannik Silvanus via llvm-commits]

Nicolai =?utf-8?q?Hähnle?= <nicolai.haehnle at amd.com>,
Nicolai =?utf-8?q?Hähnle?= <nicolai.haehnle at amd.com>,
Nicolai =?utf-8?q?Hähnle?= <nicolai.haehnle at amd.com>,
Nicolai =?utf-8?q?Hähnle?= <nicolai.haehnle at amd.com>
Message-ID:
In-Reply-To: <llvm.org/llvm/llvm-project/pull/76748 at github.com>


================
@@ -1176,20 +1215,236 @@ def may_clash_with_default_check_prefix_name(check_prefix, var):
     )
 
 
+VARIABLE_TAG = "[[@@]]"
+METAVAR_RE = re.compile(r"\[\[([A-Z0-9_]+)(?::[^]]+)?\]\]")
+NUMERIC_SUFFIX_RE = re.compile(r"[0-9]*$")
+
+
+class CheckValueInfo:
+    def __init__(
+        self,
+        nameless_value: NamelessValue,
+        var: str,
+        prefix: str,
+    ):
+        self.nameless_value = nameless_value
+        self.var = var
+        self.prefix = prefix
+
+
+class CheckLineInfo:
+    def __init__(self, line, values):
+        self.line: str = line
+        self.values: List[CheckValueInfo] = values
+
+    def __repr__(self):
+        return f"CheckLineInfo(line={self.line}, self.values={self.values})"
+
+
+def remap_metavar_names(
+    orig_line_infos: List[CheckLineInfo],
+    new_line_infos: List[CheckLineInfo],
+    committed_names: Set[str],
+) -> Mapping[str, str]:
+    """
+    Map all FileCheck variable names that appear in new_line_infos to new
+    FileCheck variable names in an attempt to reduce the diff from orig_line_infos
+    to new_line_infos.
+    """
+    # Initialize uncommitted identity mappings
+    new_mapping = {}
+    for line in new_line_infos:
+        for value in line.values:
+            new_mapping[value.var] = value.var
+
+    # Recursively commit to the identity mapping or find a better one
+    def recurse(
+        orig_line_infos: List[CheckLineInfo], new_line_infos: List[CheckLineInfo]
+    ):
+        if not new_line_infos or not orig_line_infos:
+            return
+
+        lines = set()
+
+        # Search for lines that are identical on both sides, including meta
+        # variable names, and commit to those names immediately
+        for line in orig_line_infos:
+            key = (line.line.strip(), tuple(value.var for value in line.values))
+            lines.add(key)
+
+        for line in new_line_infos:
+            key = (
+                line.line.strip(),
+                tuple(new_mapping[value.var] for value in line.values),
+            )
+            if key in lines:
+                for value in line.values:
+                    committed_names.add(new_mapping[value.var])
+
+        # Search for lines that are unique on both sides if we only consider
+        # variable names that have been committed.
----------------
jasilvanus wrote:

For my understanding: This is an artificial restriction to make the algorithm simpler, correct? 

We rely on unique lines (ignoring non-committed variable names, so initially all variable names) dividing the input into hopefully small enough chunks that again hopefully contain unique pairs?

I imagine in corner cases (e.g. similar consecutive lines differing only in variable names) this could lead to us not re-using names although we could.

https://github.com/llvm/llvm-project/pull/76748