update_test_checks: collect original check lines for old versions of lit tests (llvm#111148)

Old versions of UTC produced function labels like:

    ; CHECK-LABEL: @func(

Fix the regular expression used when scanning for old check lines to
recognize this form of label.

This allows meta variable stability to apply when running UTC on tests
using this form of label.

Reported-by: Nikita Popov <[email protected]>

Author: nhaehnle

llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/stable_ir_values2.ll

@@ -1,10 +1,9 @@
-; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 3
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
 ; RUN: opt < %s -S | FileCheck %s
 
 define i32 @func(i32 %x) {
-; CHECK-LABEL: define i32 @func(
-; CHECK-SAME: i32 [[X:%.*]]) {
-; CHECK-NEXT:    [[TMP1:%.*]] = icmp eq i32 [[X]], 0
+; CHECK-LABEL: @func(
+; CHECK-NEXT:    [[TMP1:%.*]] = icmp eq i32 [[X:.*]], 0
 ; CHECK-NEXT:    [[TMP2:%.*]] = call i32 @foo(i1 [[TMP1]])
 ; CHECK-NEXT:    [[TMP3:%.*]] = icmp eq i32 [[X]], 1
 ; CHECK-NEXT:    [[TMP4:%.*]] = call i32 @foo(i1 [[TMP3]])

llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/stable_ir_values2.ll.expected

@@ -1,10 +1,9 @@
-; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 3
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
 ; RUN: opt < %s -S | FileCheck %s
 
 define i32 @func(i32 %x) {
-; CHECK-LABEL: define i32 @func(
-; CHECK-SAME: i32 [[X:%.*]]) {
-; CHECK-NEXT:    [[TMP1:%.*]] = icmp eq i32 [[X]], 0
+; CHECK-LABEL: @func(
+; CHECK-NEXT:    [[TMP1:%.*]] = icmp eq i32 [[X:%.*]], 0
 ; CHECK-NEXT:    [[TMP6:%.*]] = call i32 @foo(i1 [[TMP1]])
 ; CHECK-NEXT:    [[TMP7:%.*]] = icmp eq i32 [[X]], 2
 ; CHECK-NEXT:    [[TMP8:%.*]] = call i32 @foo(i1 [[TMP7]])

llvm/utils/UpdateTestChecks/common.py

@@ -454,7 +454,7 @@ def collect_original_check_lines(ti: TestInfo, prefix_set: set):
                     continue
 
                 if check_kind == "LABEL":
-                    m = IR_FUNCTION_RE.match(line)
+                    m = IR_FUNCTION_LABEL_RE.match(line)
                     if m is not None:
                         func_name = m.group(1)
                         if (
@@ -572,6 +572,9 @@ def invoke_tool(exe, cmd_args, ir, preprocess_cmd=None, verbose=False):
 )
 
 IR_FUNCTION_RE = re.compile(r'^\s*define\s+(?:internal\s+)?[^@]*@"?([\w.$-]+)"?\s*\(')
+IR_FUNCTION_LABEL_RE = re.compile(
+    r'^\s*(?:define\s+(?:internal\s+)?[^@]*)?@"?([\w.$-]+)"?\s*\('
+)
 TRIPLE_IR_RE = re.compile(r'^\s*target\s+triple\s*=\s*"([^"]+)"$')
 TRIPLE_ARG_RE = re.compile(r"-m?triple[= ]([^ ]+)")
 MARCH_ARG_RE = re.compile(r"-march[= ]([^ ]+)")