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

Nicolai Hähnle via llvm-commits llvm-commits at lists.llvm.org
Tue Jan 2 12:28:29 PST 2024


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

>From c4a349b76e0478a678802ad554d8ed42a7a871e7 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Nicolai=20H=C3=A4hnle?= <nicolai.haehnle at amd.com>
Date: Thu, 23 Nov 2023 05:34:05 +0100
Subject: [PATCH 1/5] update_test_checks: precommit a test case

The test case demonstrates how meta variables are needlessly renamed,
making diffs harder to read.
---
 .../Inputs/stable_ir_values.ll                | 22 ++++++++++++++++++
 .../Inputs/stable_ir_values.ll.expected       | 23 +++++++++++++++++++
 .../update_test_checks/stable_ir_values.test  |  2 ++
 3 files changed, 47 insertions(+)
 create mode 100644 llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/stable_ir_values.ll
 create mode 100644 llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/stable_ir_values.ll.expected
 create mode 100644 llvm/test/tools/UpdateTestChecks/update_test_checks/stable_ir_values.test

diff --git a/llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/stable_ir_values.ll b/llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/stable_ir_values.ll
new file mode 100644
index 00000000000000..8457bf7dc40a2e
--- /dev/null
+++ b/llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/stable_ir_values.ll
@@ -0,0 +1,22 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 3
+; RUN: opt < %s -S | FileCheck %s
+
+; The assumption underlying this test is that there are pre-existing check lines
+; but something has changed, and we would like to avoid needless changes of
+; meta variable names so that diffs end up being easier to read, e.g. avoid
+; changing X_I33 into X_I34 or renumbering the various TMP variables.
+
+define i32 @func({i32, i32} %x, i32 %y) {
+; CHECK-LABEL: define i32 @func(
+; CHECK-SAME: { i32, i32 } [[X:%.*]], i32 [[Y:%.*]]) {
+; CHECK-NEXT:    [[X_I33:%.*]] = extractvalue { i32, i32 } [[X]], 0
+; CHECK-NEXT:    [[TMP1:%.*]] = add i32 [[X_I33]], [[Y]]
+; CHECK-NEXT:    [[TMP2:%.*]] = mul i32 [[TMP1]], 3
+; CHECK-NEXT:    ret i32 [[TMP2]]
+;
+  %x.i34 = extractvalue {i32, i32} %x, 0
+  %1 = add i32 %y, 1
+  %2 = add i32 %x.i34, %1
+  %3 = mul i32 %2, 3
+  ret i32 %3
+}
diff --git a/llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/stable_ir_values.ll.expected b/llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/stable_ir_values.ll.expected
new file mode 100644
index 00000000000000..5142e3ed32ba45
--- /dev/null
+++ b/llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/stable_ir_values.ll.expected
@@ -0,0 +1,23 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 3
+; RUN: opt < %s -S | FileCheck %s
+
+; The assumption underlying this test is that there are pre-existing check lines
+; but something has changed, and we would like to avoid needless changes of
+; meta variable names so that diffs end up being easier to read, e.g. avoid
+; changing X_I33 into X_I34 or renumbering the various TMP variables.
+
+define i32 @func({i32, i32} %x, i32 %y) {
+; CHECK-LABEL: define i32 @func(
+; CHECK-SAME: { i32, i32 } [[X:%.*]], i32 [[Y:%.*]]) {
+; CHECK-NEXT:    [[X_I34:%.*]] = extractvalue { i32, i32 } [[X]], 0
+; CHECK-NEXT:    [[TMP1:%.*]] = add i32 [[Y]], 1
+; CHECK-NEXT:    [[TMP2:%.*]] = add i32 [[X_I34]], [[TMP1]]
+; CHECK-NEXT:    [[TMP3:%.*]] = mul i32 [[TMP2]], 3
+; CHECK-NEXT:    ret i32 [[TMP3]]
+;
+  %x.i34 = extractvalue {i32, i32} %x, 0
+  %1 = add i32 %y, 1
+  %2 = add i32 %x.i34, %1
+  %3 = mul i32 %2, 3
+  ret i32 %3
+}
diff --git a/llvm/test/tools/UpdateTestChecks/update_test_checks/stable_ir_values.test b/llvm/test/tools/UpdateTestChecks/update_test_checks/stable_ir_values.test
new file mode 100644
index 00000000000000..c6287a6b29ca92
--- /dev/null
+++ b/llvm/test/tools/UpdateTestChecks/update_test_checks/stable_ir_values.test
@@ -0,0 +1,2 @@
+# RUN: cp -f %S/Inputs/stable_ir_values.ll %t.ll && %update_test_checks %t.ll
+# RUN: diff -u %t.ll %S/Inputs/stable_ir_values.ll.expected

>From 6667cf8dc6db9045a9c59ae2e7f1c992bc29adb9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Nicolai=20H=C3=A4hnle?= <nicolai.haehnle at amd.com>
Date: Sat, 23 Dec 2023 14:07:47 +0100
Subject: [PATCH 2/5] update_test_checks: simplify is_local_def_ir_value

The match argument is unused.
---
 llvm/utils/UpdateTestChecks/common.py | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/llvm/utils/UpdateTestChecks/common.py b/llvm/utils/UpdateTestChecks/common.py
index 0fe0dfc506b059..27602f0671e288 100644
--- a/llvm/utils/UpdateTestChecks/common.py
+++ b/llvm/utils/UpdateTestChecks/common.py
@@ -922,7 +922,7 @@ def __init__(
         self.variable_mapping = {}
 
     # Return true if this kind of IR value is "local", basically if it matches '%{{.*}}'.
-    def is_local_def_ir_value_match(self, match):
+    def is_local_def_ir_value(self):
         return self.ir_prefix == "%"
 
     # Return true if this kind of IR value is "global", basically if it matches '#{{.*}}'.
@@ -938,7 +938,7 @@ def get_ir_prefix_from_ir_value_match(self, match):
     # Return the IR regexp we use for this kind or IR value, e.g., [\w.-]+? for locals
     def get_ir_regex_from_ir_value_re_match(self, match):
         # for backwards compatibility we check locals with '.*'
-        if self.is_local_def_ir_value_match(match):
+        if self.is_local_def_ir_value():
             return ".*"
         return self.ir_regexp
 
@@ -979,7 +979,7 @@ def get_value_definition(self, var, match):
         else:
             regex = self.get_ir_regex_from_ir_value_re_match(match)
             capture_start = "[["
-        if self.is_local_def_ir_value_match(match):
+        if self.is_local_def_ir_value():
             return capture_start + varname + ":" + prefix + regex + "]]"
         return prefix + capture_start + varname + ":" + regex + "]]"
 
@@ -988,7 +988,7 @@ def get_value_use(self, var, match, var_prefix=None):
         if var_prefix is None:
             var_prefix = self.check_prefix
         capture_start = "[[#" if self.is_number else "[["
-        if self.is_local_def_ir_value_match(match):
+        if self.is_local_def_ir_value():
             return capture_start + self.get_value_name(var, var_prefix) + "]]"
         prefix = self.get_ir_prefix_from_ir_value_match(match)[0]
         return prefix + capture_start + self.get_value_name(var, var_prefix) + "]]"
@@ -1198,7 +1198,7 @@ def transform_line_vars(match):
                 " with scripted FileCheck name." % (var,)
             )
         key = (var, nameless_value.check_key)
-        is_local_def = nameless_value.is_local_def_ir_value_match(match)
+        is_local_def = nameless_value.is_local_def_ir_value()
         if is_local_def and key in vars_seen:
             rv = nameless_value.get_value_use(var, match)
         elif not is_local_def and key in global_vars_seen:

>From ef2ed94feacf85a52c9b1842572bff8d63d104fc Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Nicolai=20H=C3=A4hnle?= <nicolai.haehnle at amd.com>
Date: Sat, 23 Dec 2023 14:20:43 +0100
Subject: [PATCH 3/5] update_test_checks: simplify get_ir_regex

The match argument isn't used.
---
 llvm/utils/UpdateTestChecks/common.py | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/llvm/utils/UpdateTestChecks/common.py b/llvm/utils/UpdateTestChecks/common.py
index 27602f0671e288..3898b269a80901 100644
--- a/llvm/utils/UpdateTestChecks/common.py
+++ b/llvm/utils/UpdateTestChecks/common.py
@@ -936,7 +936,7 @@ def get_ir_prefix_from_ir_value_match(self, match):
         return re.search(self.ir_prefix, match[0])[0], self.check_prefix
 
     # Return the IR regexp we use for this kind or IR value, e.g., [\w.-]+? for locals
-    def get_ir_regex_from_ir_value_re_match(self, match):
+    def get_ir_regex(self):
         # for backwards compatibility we check locals with '.*'
         if self.is_local_def_ir_value():
             return ".*"
@@ -977,7 +977,7 @@ def get_value_definition(self, var, match):
             regex = ""  # always capture a number in the default format
             capture_start = "[[#"
         else:
-            regex = self.get_ir_regex_from_ir_value_re_match(match)
+            regex = self.get_ir_regex()
             capture_start = "[["
         if self.is_local_def_ir_value():
             return capture_start + varname + ":" + prefix + regex + "]]"

>From 3e8a784b24aeda372e5900922886ac4eb34f1eb0 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Nicolai=20H=C3=A4hnle?= <nicolai.haehnle at amd.com>
Date: Thu, 23 Nov 2023 06:46:07 +0100
Subject: [PATCH 4/5] update_test_checks: keep meta variables stable by default

Prior to this change, running UTC on larger tests, especially tests
with unnamed IR values, often resulted in a spuriously large diff
because e.g. TMPnn variables in the CHECK lines were renumbered. This
change attempts to reduce the diff by keeping those variable names the
same.

There are cases in which this "drift" of variable names can end up being
more confusing. The old behavior can be re-enabled with the
--reset-variable-names command line argument.

The improvement may not be immediately apparent in the diff of this change.
The point is that the diff of stable_ir_values.ll against
stable_ir_values.ll.expected after this change is smaller.

Ideally, we'd also keep meta variables for "global" objects stable, e.g.
for attributes (#nn) and metadata (!nn). However, that would require a
much more substantial refactoring of how we generate check lines, so I
left it for future work.
---
 .../Inputs/stable_ir_values.ll.expected       |  10 +-
 .../Inputs/stable_ir_values.ll.expected.reset |  23 +
 .../update_test_checks/stable_ir_values.test  |   3 +
 llvm/utils/UpdateTestChecks/common.py         | 418 +++++++++++++++++-
 llvm/utils/update_test_checks.py              |  21 +-
 5 files changed, 448 insertions(+), 27 deletions(-)
 create mode 100644 llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/stable_ir_values.ll.expected.reset

diff --git a/llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/stable_ir_values.ll.expected b/llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/stable_ir_values.ll.expected
index 5142e3ed32ba45..3549a4d76aa762 100644
--- a/llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/stable_ir_values.ll.expected
+++ b/llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/stable_ir_values.ll.expected
@@ -9,11 +9,11 @@
 define i32 @func({i32, i32} %x, i32 %y) {
 ; CHECK-LABEL: define i32 @func(
 ; CHECK-SAME: { i32, i32 } [[X:%.*]], i32 [[Y:%.*]]) {
-; CHECK-NEXT:    [[X_I34:%.*]] = extractvalue { i32, i32 } [[X]], 0
-; CHECK-NEXT:    [[TMP1:%.*]] = add i32 [[Y]], 1
-; CHECK-NEXT:    [[TMP2:%.*]] = add i32 [[X_I34]], [[TMP1]]
-; CHECK-NEXT:    [[TMP3:%.*]] = mul i32 [[TMP2]], 3
-; CHECK-NEXT:    ret i32 [[TMP3]]
+; CHECK-NEXT:    [[X_I33:%.*]] = extractvalue { i32, i32 } [[X]], 0
+; CHECK-NEXT:    [[TMP3:%.*]] = add i32 [[Y]], 1
+; CHECK-NEXT:    [[TMP1:%.*]] = add i32 [[X_I33]], [[TMP3]]
+; CHECK-NEXT:    [[TMP2:%.*]] = mul i32 [[TMP1]], 3
+; CHECK-NEXT:    ret i32 [[TMP2]]
 ;
   %x.i34 = extractvalue {i32, i32} %x, 0
   %1 = add i32 %y, 1
diff --git a/llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/stable_ir_values.ll.expected.reset b/llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/stable_ir_values.ll.expected.reset
new file mode 100644
index 00000000000000..5142e3ed32ba45
--- /dev/null
+++ b/llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/stable_ir_values.ll.expected.reset
@@ -0,0 +1,23 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 3
+; RUN: opt < %s -S | FileCheck %s
+
+; The assumption underlying this test is that there are pre-existing check lines
+; but something has changed, and we would like to avoid needless changes of
+; meta variable names so that diffs end up being easier to read, e.g. avoid
+; changing X_I33 into X_I34 or renumbering the various TMP variables.
+
+define i32 @func({i32, i32} %x, i32 %y) {
+; CHECK-LABEL: define i32 @func(
+; CHECK-SAME: { i32, i32 } [[X:%.*]], i32 [[Y:%.*]]) {
+; CHECK-NEXT:    [[X_I34:%.*]] = extractvalue { i32, i32 } [[X]], 0
+; CHECK-NEXT:    [[TMP1:%.*]] = add i32 [[Y]], 1
+; CHECK-NEXT:    [[TMP2:%.*]] = add i32 [[X_I34]], [[TMP1]]
+; CHECK-NEXT:    [[TMP3:%.*]] = mul i32 [[TMP2]], 3
+; CHECK-NEXT:    ret i32 [[TMP3]]
+;
+  %x.i34 = extractvalue {i32, i32} %x, 0
+  %1 = add i32 %y, 1
+  %2 = add i32 %x.i34, %1
+  %3 = mul i32 %2, 3
+  ret i32 %3
+}
diff --git a/llvm/test/tools/UpdateTestChecks/update_test_checks/stable_ir_values.test b/llvm/test/tools/UpdateTestChecks/update_test_checks/stable_ir_values.test
index c6287a6b29ca92..4dfaf5d25c8a69 100644
--- a/llvm/test/tools/UpdateTestChecks/update_test_checks/stable_ir_values.test
+++ b/llvm/test/tools/UpdateTestChecks/update_test_checks/stable_ir_values.test
@@ -1,2 +1,5 @@
 # RUN: cp -f %S/Inputs/stable_ir_values.ll %t.ll && %update_test_checks %t.ll
 # RUN: diff -u %t.ll %S/Inputs/stable_ir_values.ll.expected
+# Now test that we can reset all the names
+# RUN: %update_test_checks %t.ll --reset-variable-names
+# RUN: diff -u %t.ll %S/Inputs/stable_ir_values.ll.expected.reset
diff --git a/llvm/utils/UpdateTestChecks/common.py b/llvm/utils/UpdateTestChecks/common.py
index 3898b269a80901..9c669e86f530a9 100644
--- a/llvm/utils/UpdateTestChecks/common.py
+++ b/llvm/utils/UpdateTestChecks/common.py
@@ -1,6 +1,8 @@
 from __future__ import print_function
 
 import argparse
+import bisect
+import collections
 import copy
 import glob
 import itertools
@@ -10,7 +12,7 @@
 import sys
 import shlex
 
-from typing import List
+from typing import List, Mapping, Set
 
 ##### Common utilities for update_*test_checks.py
 
@@ -410,6 +412,42 @@ def should_add_line_to_output(
     return True
 
 
+def collect_original_check_lines(original_check_lines, ti: TestInfo, prefix_set: set):
+    """
+    Collect pre-existing check lines in a the dictionary original_check_lines.
+    original_check_lines[func_name][prefix] is filled with a list of
+    right-hand-sides of check lines.
+    """
+    in_function_start = None
+    for input_line_info in ti.ro_iterlines():
+        input_line = input_line_info.line
+        if in_function_start is not None:
+            if input_line == "":
+                continue
+            if input_line.lstrip().startswith(";"):
+                m = CHECK_RE.match(input_line)
+                if (
+                    m is not None
+                    and m.group(1) in prefix_set
+                    and m.group(2) not in ["LABEL", "SAME"]
+                ):
+                    if m.group(1) not in in_function_start:
+                        in_function_start[m.group(1)] = []
+                    in_function_start[m.group(1)].append(
+                        input_line[m.span()[1] :].strip()
+                    )
+                continue
+            in_function_start = None
+
+        m = IR_FUNCTION_RE.match(input_line)
+        if m is not None:
+            func_name = m.group(1)
+            if ti.args.function is not None and func_name != ti.args.function:
+                # When filtering on a specific function, skip all others.
+                continue
+
+            in_function_start = original_check_lines[func_name] = {}
+
 # Perform lit-like substitutions
 def getSubstitutions(sourcepath):
     sourcedir = os.path.dirname(sourcepath)
@@ -481,7 +519,7 @@ def invoke_tool(exe, cmd_args, ir, preprocess_cmd=None, verbose=False):
 CHECK_PREFIX_RE = re.compile(r"--?check-prefix(?:es)?[= ](\S+)")
 PREFIX_RE = re.compile("^[a-zA-Z0-9_-]+$")
 CHECK_RE = re.compile(
-    r"^\s*(?://|[;#])\s*([^:]+?)(?:-NEXT|-NOT|-DAG|-LABEL|-SAME|-EMPTY)?:"
+    r"^\s*(?://|[;#])\s*([^:]+?)(?:-(NEXT|NOT|DAG|LABEL|SAME|EMPTY))?:"
 )
 
 UTC_ARGS_KEY = "UTC_ARGS:"
@@ -1176,20 +1214,236 @@ 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.
+        lines = collections.defaultdict(lambda: [None, None])
+        for i, line in enumerate(orig_line_infos):
+            key = (
+                line.line.strip(),
+                tuple(
+                    value.var for value in line.values if value.var in committed_names
+                ),
+            )
+            entry = lines[key]
+            if entry[0] is None:
+                entry[0] = i
+            else:
+                entry[0] = False
+
+        for i, line in enumerate(new_line_infos):
+            key = (
+                line.line.strip(),
+                tuple(
+                    new_mapping[value.var]
+                    for value in line.values
+                    if new_mapping[value.var] in committed_names
+                ),
+            )
+            entry = lines[key]
+            if entry[1] is None:
+                entry[1] = i
+            else:
+                entry[1] = False
+
+        unique_matches = []
+        for entry in lines.values():
+            if (
+                entry[0] is not None
+                and entry[0] is not False
+                and entry[1] is not None
+                and entry[1] is not False
+            ):
+                unique_matches.append((entry[0], entry[1]))
+
+        if not unique_matches:
+            # There are no unique matches. This is the recursion base case.
+            return
+
+        # Compute a maximal crossing-free matching via dynamic programming
+        unique_matches.sort(key=lambda entry: entry[0])
+
+        backlinks = []
+        table = []
+        for _, new_idx in unique_matches:
+            ti = bisect.bisect_left(table, new_idx, key=lambda entry: entry[0])
+            if ti < len(table):
+                table[ti] = (new_idx, len(backlinks))
+            else:
+                table.append((new_idx, len(backlinks)))
+            if ti > 0:
+                backlinks.append(table[ti - 1][1])
+            else:
+                backlinks.append(None)
+
+        # Commit to names in the matching, re-checking compatibility as we go along
+        match_idx = table[-1][1]
+        matches = [(len(orig_line_infos), len(new_line_infos))]
+        while match_idx is not None:
+            orig_idx, new_idx = unique_matches[match_idx]
+            local_commits = {}
+
+            for orig_value, new_value in zip(
+                orig_line_infos[orig_idx].values, new_line_infos[new_idx].values
+            ):
+                if new_mapping[new_value.var] in committed_names:
+                    # The new value has already been committed by a previous match we considered
+                    # during the outer loop. If it was mapped to the same name as the original value,
+                    # we can consider committing other values from this line. Otherwise, we should
+                    # ignore this line.
+                    if new_mapping[new_value.var] == orig_value.var:
+                        continue
+                    else:
+                        break
+
+                if new_value.var in local_commits:
+                    # Same, but for a possible commit happening on the same line
+                    if local_commits[new_value.var] == orig_value.var:
+                        continue
+                    else:
+                        break
+
+                if orig_value.var in committed_names:
+                    # We can't map this value because the name we would map it to has already been
+                    # committed for something else. Give up on this line.
+                    break
+
+                local_commits[new_value.var] = orig_value.var
+            else:
+                # No reason not to add any commitments for this line
+                for new_var, orig_var in local_commits.items():
+                    new_mapping[new_var] = orig_var
+                    committed_names.add(orig_var)
+
+                    if (
+                        orig_var != new_var
+                        and orig_var in new_mapping
+                        and new_mapping[orig_var] == orig_var
+                    ):
+                        new_mapping[orig_var] = "conflict_" + orig_var
+
+                matches.append((orig_idx, new_idx))
+
+            match_idx = backlinks[match_idx]
+
+        # Recurse
+        prev_orig_idx = -1
+        prev_new_idx = -1
+        for orig_idx, new_idx in reversed(matches):
+            recurse(
+                orig_line_infos[prev_orig_idx + 1 : orig_idx],
+                new_line_infos[prev_new_idx + 1 : new_idx],
+            )
+            prev_orig_idx = orig_idx
+            prev_new_idx = new_idx
+
+    recurse(orig_line_infos, new_line_infos)
+
+    # Commit to remaining names and resolve conflicts
+    for new_name, mapped_name in new_mapping.items():
+        if mapped_name in committed_names:
+            continue
+        if not mapped_name.startswith("conflict_"):
+            assert mapped_name == new_name
+            committed_names.add(mapped_name)
+
+    for new_name, mapped_name in new_mapping.items():
+        if mapped_name in committed_names:
+            continue
+        assert mapped_name.startswith("conflict_")
+
+        m = NUMERIC_SUFFIX_RE.search(new_name)
+        base_name = new_name[: m.span()[0]]
+        suffix = int(new_name[m.span()[0] :]) if m.span()[0] != m.span()[1] else 1
+        while True:
+            candidate = f"{base_name}{suffix}"
+            if candidate not in committed_names:
+                new_mapping[new_name] = candidate
+                break
+            suffix += 1
+
+    return new_mapping
+
 def generalize_check_lines_common(
     lines,
     is_analyze,
     vars_seen,
     global_vars_seen,
     nameless_values,
-    nameless_value_regex,
+    nameless_value_regex: re.Pattern,
     is_asm,
     preserve_names,
+    original_check_lines: List[str] | None = None,
 ):
     # This gets called for each match that occurs in
     # a line. We transform variables we haven't seen
     # into defs, and variables we have seen into uses.
-    def transform_line_vars(match):
+    def transform_line_vars(match, transform_locals=True):
         var = get_name_from_ir_value_match(match)
         nameless_value = get_nameless_value_from_match(match, nameless_values)
         if may_clash_with_default_check_prefix_name(nameless_value.check_prefix, var):
@@ -1199,6 +1453,8 @@ def transform_line_vars(match):
             )
         key = (var, nameless_value.check_key)
         is_local_def = nameless_value.is_local_def_ir_value()
+        if is_local_def and not transform_locals:
+            return None
         if is_local_def and key in vars_seen:
             rv = nameless_value.get_value_use(var, match)
         elif not is_local_def and key in global_vars_seen:
@@ -1217,13 +1473,15 @@ def transform_line_vars(match):
         # including the commas and spaces.
         return match.group(1) + rv + match.group(match.lastindex)
 
-    lines_with_def = []
+    def transform_non_local_line_vars(match):
+        return transform_line_vars(match, False)
+
     multiple_braces_re = re.compile(r"({{+)|(}}+)")
     def escape_braces(match_obj):
         return '{{' + re.escape(match_obj.group(0)) + '}}'
 
-    for i, line in enumerate(lines):
-        if not is_asm and not is_analyze:
+    if not is_asm and not is_analyze:
+        for i, line in enumerate(lines):
             # An IR variable named '%.' matches the FileCheck regex string.
             line = line.replace("%.", "%dot")
             for regex in _global_hex_value_regex:
@@ -1241,25 +1499,136 @@ def escape_braces(match_obj):
             # Ignore any comments, since the check lines will too.
             scrubbed_line = SCRUB_IR_COMMENT_RE.sub(r"", line)
             lines[i] = scrubbed_line
-        if not preserve_names:
-            # It can happen that two matches are back-to-back and for some reason sub
-            # will not replace both of them. For now we work around this by
-            # substituting until there is no more match.
-            changed = True
-            while changed:
-                (lines[i], changed) = nameless_value_regex.subn(
-                    transform_line_vars, lines[i], count=1
-                )
-        if is_analyze:
+
+    if not preserve_names:
+        if is_asm:
+            for i, _ in enumerate(lines):
+                # It can happen that two matches are back-to-back and for some reason sub
+                # will not replace both of them. For now we work around this by
+                # substituting until there is no more match.
+                changed = True
+                while changed:
+                    (lines[i], changed) = nameless_value_regex.subn(
+                        transform_line_vars, lines[i], count=1
+                    )
+        else:
+            # LLVM IR case. Start by handling global meta variables (global IR variables,
+            # metadata, attributes)
+            for i, _ in enumerate(lines):
+                start = 0
+                while True:
+                    m = nameless_value_regex.search(lines[i][start:])
+                    if m is None:
+                        break
+                    start += m.span()[0]
+                    sub = transform_non_local_line_vars(m)
+                    if sub is not None:
+                        lines[i] = (
+                            lines[i][:start] + sub + lines[i][start + len(m.group(0)) :]
+                        )
+                    start += 1
+
+            # Collect information about new check lines and original check lines (if any)
+            new_line_infos = []
+            for line in lines:
+                filtered_line = ""
+                values = []
+                while True:
+                    m = nameless_value_regex.search(line)
+                    if m is None:
+                        filtered_line += line
+                        break
+
+                    var = get_name_from_ir_value_match(m)
+                    nameless_value = get_nameless_value_from_match(m, nameless_values)
+                    var = nameless_value.get_value_name(
+                        var, nameless_value.check_prefix
+                    )
+
+                    # Replace with a [[@@]] tag, but be sure to keep the spaces and commas.
+                    filtered_line += (
+                        line[: m.span()[0]]
+                        + m.group(1)
+                        + VARIABLE_TAG
+                        + m.group(m.lastindex)
+                    )
+                    line = line[m.span()[1] :]
+                    values.append(
+                        CheckValueInfo(
+                            nameless_value=nameless_value,
+                            var=var,
+                            prefix=nameless_value.get_ir_prefix_from_ir_value_match(m)[
+                                0
+                            ],
+                        )
+                    )
+                new_line_infos.append(CheckLineInfo(filtered_line, values))
+
+            orig_line_infos = []
+            for line in original_check_lines or []:
+                filtered_line = ""
+                values = []
+                while True:
+                    m = METAVAR_RE.search(line)
+                    if m is None:
+                        filtered_line += line
+                        break
+
+                    # Replace with a [[@@]] tag, but be sure to keep the spaces and commas.
+                    filtered_line += line[: m.span()[0]] + VARIABLE_TAG
+                    line = line[m.span()[1] :]
+                    values.append(
+                        CheckValueInfo(
+                            nameless_value=None,
+                            var=m.group(1),
+                            prefix=None,
+                        )
+                    )
+                orig_line_infos.append(CheckLineInfo(filtered_line, values))
+
+            # Compute the variable name mapping
+            committed_names = set(vars_seen)
+
+            mapping = remap_metavar_names(
+                orig_line_infos, new_line_infos, committed_names
+            )
+
+            for i, line_info in enumerate(new_line_infos):
+                line_template = line_info.line
+                line = ""
+
+                for value in line_info.values:
+                    idx = line_template.find(VARIABLE_TAG)
+                    line += line_template[:idx]
+                    line_template = line_template[idx + len(VARIABLE_TAG) :]
+
+                    key = (mapping[value.var], nameless_value.check_key)
+                    is_local_def = nameless_value.is_local_def_ir_value()
+                    if is_local_def:
+                        if mapping[value.var] in vars_seen:
+                            line += f"[[{mapping[value.var]}]]"
+                        else:
+                            line += f"[[{mapping[value.var]}:{value.prefix}{value.nameless_value.get_ir_regex()}]]"
+                            vars_seen.add(mapping[value.var])
+                    else:
+                        todo("not implemented")
+
+                line += line_template
+
+                lines[i] = line
+
+    if is_analyze:
+        for i, _ in enumerate(lines):
             # Escape multiple {{ or }} as {{}} denotes a FileCheck regex.
             scrubbed_line = multiple_braces_re.sub(escape_braces, lines[i])
             lines[i] = scrubbed_line
+
     return lines
 
 
 # Replace IR value defs and uses with FileCheck variables.
 def generalize_check_lines(
-    lines, is_analyze, vars_seen, global_vars_seen, preserve_names
+    lines, is_analyze, vars_seen, global_vars_seen, preserve_names, original_check_lines
 ):
     return generalize_check_lines_common(
         lines,
@@ -1270,6 +1639,7 @@ def generalize_check_lines(
         IR_VALUE_RE,
         False,
         preserve_names,
+        original_check_lines=original_check_lines,
     )
 
 
@@ -1326,6 +1696,7 @@ def add_checks(
     global_vars_seen_dict,
     is_filtered,
     preserve_names=False,
+    original_check_lines: Mapping[str, List[str]] = {},
 ):
     # prefix_exclusions are prefixes we cannot use to print the function because it doesn't exist in run lines that use these prefixes as well.
     prefix_exclusions = set()
@@ -1398,6 +1769,7 @@ def add_checks(
                     vars_seen,
                     global_vars_seen,
                     preserve_names,
+                    original_check_lines=[],
                 )[0]
             func_name_separator = func_dict[checkprefix][func_name].func_name_separator
             if "[[" in args_and_sig:
@@ -1505,7 +1877,12 @@ def add_checks(
             # to variable naming fashions.
             else:
                 func_body = generalize_check_lines(
-                    func_body, False, vars_seen, global_vars_seen, preserve_names
+                    func_body,
+                    False,
+                    vars_seen,
+                    global_vars_seen,
+                    preserve_names,
+                    original_check_lines=original_check_lines.get(checkprefix),
                 )
 
                 # This could be selectively enabled with an optional invocation argument.
@@ -1567,6 +1944,7 @@ def add_ir_checks(
     version,
     global_vars_seen_dict,
     is_filtered,
+    original_check_lines={},
 ):
     # Label format is based on IR string.
     if function_sig and version > 1:
@@ -1591,6 +1969,7 @@ def add_ir_checks(
         global_vars_seen_dict,
         is_filtered,
         preserve_names,
+        original_check_lines=original_check_lines,
     )
 
 
@@ -1879,6 +2258,7 @@ def get_autogennote_suffix(parser, args):
             "llvm_bin",
             "verbose",
             "force_update",
+            "reset_variable_names",
         ):
             continue
         value = getattr(args, action.dest)
diff --git a/llvm/utils/update_test_checks.py b/llvm/utils/update_test_checks.py
index 06c247c8010a90..0a2f7763323a11 100755
--- a/llvm/utils/update_test_checks.py
+++ b/llvm/utils/update_test_checks.py
@@ -85,6 +85,12 @@ def main():
         choices=["none", "smart", "all"],
         help="Check global entries (global variables, metadata, attribute sets, ...) for functions",
     )
+    parser.add_argument(
+        "--reset-variable-names",
+        action="store_true",
+        help="Reset all variable names to correspond closely to the variable names in IR. "
+        "This tends to result in larger diffs.",
+    )
     parser.add_argument("tests", nargs="+")
     initial_args = common.parse_commandline_args(parser)
 
@@ -170,13 +176,18 @@ def main():
             )
             builder.processed_prefixes(prefixes)
 
+        prefix_set = set(
+            [prefix for prefixes, _, _ in prefix_list for prefix in prefixes]
+        )
+
+        original_check_lines = {}
+        if not ti.args.reset_variable_names:
+            common.collect_original_check_lines(original_check_lines, ti, prefix_set)
+
         func_dict = builder.finish_and_get_func_dict()
         is_in_function = False
         is_in_function_start = False
         has_checked_pre_function_globals = False
-        prefix_set = set(
-            [prefix for prefixes, _, _ in prefix_list for prefix in prefixes]
-        )
         common.debug("Rewriting FileCheck prefixes:", str(prefix_set))
         output_lines = []
 
@@ -230,6 +241,7 @@ def main():
                         args.version,
                         global_vars_seen_dict,
                         is_filtered=builder.is_filtered(),
+                        original_check_lines=original_check_lines.get(func, {}),
                     ),
                 )
             )
@@ -260,6 +272,9 @@ def main():
                             args.version,
                             global_vars_seen_dict,
                             is_filtered=builder.is_filtered(),
+                            original_check_lines=original_check_lines.get(
+                                func_name, {}
+                            ),
                         )
                     )
                     is_in_function_start = False

>From 2d86c4e01318b9dbff4a19ee811d0b1844f997dc Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Nicolai=20H=C3=A4hnle?= <nicolai.haehnle at amd.com>
Date: Tue, 2 Jan 2024 20:11:36 +0100
Subject: [PATCH 5/5] fixup! update_test_checks: keep meta variables stable by
 default

---
 llvm/utils/UpdateTestChecks/common.py | 1 +
 1 file changed, 1 insertion(+)

diff --git a/llvm/utils/UpdateTestChecks/common.py b/llvm/utils/UpdateTestChecks/common.py
index 9c669e86f530a9..dc6bdda097a1e4 100644
--- a/llvm/utils/UpdateTestChecks/common.py
+++ b/llvm/utils/UpdateTestChecks/common.py
@@ -448,6 +448,7 @@ def collect_original_check_lines(original_check_lines, ti: TestInfo, prefix_set:
 
             in_function_start = original_check_lines[func_name] = {}
 
+
 # Perform lit-like substitutions
 def getSubstitutions(sourcepath):
     sourcedir = os.path.dirname(sourcepath)



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