[UTC] Don't leave dangling CHECK-SAME when removing CHECK lines (llvm#82569)

When removing only lines that are global value CHECK lines, a related
CHECK-SAME line could be left dangling without a previous line to belong
to.

Resolves llvm#78517

Author: hnrklssn

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

@@ -0,0 +1,15 @@
+; RUN: opt -S < %s | FileCheck %s
+
+define i32 @foo() {
+; CHECK-LABEL: @foo(
+; CHECK-NEXT:    [[RESULT:%.*]] = call i32 @bar(i32 0, i32 1)
+; CHECK-NEXT:    ret i32 [[RESULT]]
+;
+  %result = call i32 @bar(i32 0, i32 1)
+  ret i32 %result
+}
+
+declare i32 @bar(i32, i32)
+; CHECK-LABEL: @bar(
+; CHECK-SAME: i32
+; CHECK-SAME: i32

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

@@ -0,0 +1,13 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt -S < %s | FileCheck %s
+
+define i32 @foo() {
+; CHECK-LABEL: @foo(
+; CHECK-NEXT:    [[RESULT:%.*]] = call i32 @bar(i32 0, i32 1)
+; CHECK-NEXT:    ret i32 [[RESULT]]
+;
+  %result = call i32 @bar(i32 0, i32 1)
+  ret i32 %result
+}
+
+declare i32 @bar(i32, i32)

llvm/test/tools/UpdateTestChecks/update_test_checks/global_remove_same.test

@@ -0,0 +1,4 @@
+## Basic test checking global checks split over multiple lines are removed together
+# RUN: cp -f %S/Inputs/global_remove_same.ll %t.ll && %update_test_checks %t.ll
+# RUN: diff -u %t.ll %S/Inputs/global_remove_same.ll.expected
+

llvm/utils/UpdateTestChecks/common.py

@@ -388,7 +388,12 @@ def itertests(
 
 
 def should_add_line_to_output(
-    input_line, prefix_set, skip_global_checks=False, comment_marker=";"
+    input_line,
+    prefix_set,
+    *,
+    skip_global_checks=False,
+    skip_same_checks=False,
+    comment_marker=";",
 ):
     # Skip any blank comment lines in the IR.
     if not skip_global_checks and input_line.strip() == comment_marker:
@@ -402,9 +407,14 @@ def should_add_line_to_output(
     # And skip any CHECK lines. We're building our own.
     m = CHECK_RE.match(input_line)
     if m and m.group(1) in prefix_set:
+        if skip_same_checks and CHECK_SAME_RE.match(input_line):
+            # The previous CHECK line was removed, so don't leave this dangling
+            return False
         if skip_global_checks:
+            # Skip checks only if they are of global value definitions
             global_ir_value_re = re.compile(r"(\[\[|@)", flags=(re.M))
-            return not global_ir_value_re.search(input_line)
+            is_global = global_ir_value_re.search(input_line)
+            return not is_global
         return False
 
     return True
@@ -483,6 +493,7 @@ def invoke_tool(exe, cmd_args, ir, preprocess_cmd=None, verbose=False):
 CHECK_RE = re.compile(
     r"^\s*(?://|[;#])\s*([^:]+?)(?:-NEXT|-NOT|-DAG|-LABEL|-SAME|-EMPTY)?:"
 )
+CHECK_SAME_RE = re.compile(r"^\s*(?://|[;#])\s*([^:]+?)(?:-SAME)?:")
 
 UTC_ARGS_KEY = "UTC_ARGS:"
 UTC_ARGS_CMD = re.compile(r".*" + UTC_ARGS_KEY + r"\s*(?P<cmd>.*)\s*$")

llvm/utils/update_test_checks.py

@@ -235,6 +235,7 @@ def main():
             )
         else:
             # "Normal" mode.
+            dropped_previous_line = False
             for input_line_info in ti.iterlines(output_lines):
                 input_line = input_line_info.line
                 args = input_line_info.args
@@ -282,17 +283,24 @@ def main():
                     has_checked_pre_function_globals = True
 
                 if common.should_add_line_to_output(
-                    input_line, prefix_set, not is_in_function
+                    input_line,
+                    prefix_set,
+                    skip_global_checks=not is_in_function,
+                    skip_same_checks=dropped_previous_line,
                 ):
                     # This input line of the function body will go as-is into the output.
                     # Except make leading whitespace uniform: 2 spaces.
                     input_line = common.SCRUB_LEADING_WHITESPACE_RE.sub(
                         r"  ", input_line
                     )
                     output_lines.append(input_line)
+                    dropped_previous_line = False
                     if input_line.strip() == "}":
                         is_in_function = False
                         continue
+                else:
+                    # If we are removing a check line, and the next line is CHECK-SAME, it MUST also be removed
+                    dropped_previous_line = True
 
                 if is_in_function:
                     continue