improved commentary

Author: vpykhtin

llvm/test/tools/UpdateTestChecks/update_llc_test_checks/Inputs/x86_asm_mir_same_prefix.ll

@@ -1,4 +1,3 @@
-; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
 ; RUN: llc -mtriple=x86_64 < %s | FileCheck %s --check-prefix=CHECK
 ; RUN: llc -mtriple=x86_64 -stop-after=finalize-isel < %s | FileCheck %s --check-prefix=CHECK
 
@@ -12,5 +11,3 @@ define i32 @sub(i32 %a, i32 %b) {
   ret i32 %diff
 }
 
-;; NOTE: These prefixes are unused and the list is autogenerated. Do not add tests below this line:
-; CHECK: {{.*}}

llvm/test/tools/UpdateTestChecks/update_llc_test_checks/x86-asm-mir-mixed.test

@@ -3,6 +3,7 @@
 
 # RUN: cp -f %S/Inputs/x86_asm_mir_mixed.ll %t.ll && %update_llc_test_checks %t.ll
 # RUN: diff -u %S/Inputs/x86_asm_mir_mixed.ll.expected %t.ll
+
 ## Verify that running the script again on an already updated file doesn't add duplicate checks
 # RUN: %update_llc_test_checks %t.ll
 # RUN: diff -u %S/Inputs/x86_asm_mir_mixed.ll.expected %t.ll

llvm/test/tools/UpdateTestChecks/update_llc_test_checks/x86-asm-mir-same-prefix.test

@@ -1,5 +1,5 @@
 ## Test that using the same prefix for both ASM and MIR outputs generates a warning
-## and only produces ASM checks (not MIR checks).
+## and doesn't produce any checks.
 
 # RUN: cp -f %S/Inputs/x86_asm_mir_same_prefix.ll %t.ll && %update_llc_test_checks %t.ll 2>&1 | FileCheck %s --check-prefix=WARNING
 # RUN: diff -u %S/Inputs/x86_asm_mir_same_prefix.ll.expected %t.ll

llvm/utils/UpdateTestChecks/mir.py

@@ -170,6 +170,7 @@ def add_mir_checks_for_function(
         for prefix in run[0]:
             if prefix in printed_prefixes:
                 break
+            # func_info can be empty if there was a prefix conflict.
             if not func_dict[prefix].get(func_name):
                 continue
             if printed_prefixes:
@@ -223,7 +224,6 @@ def add_mir_check_lines(
     first_line = func_body[0]
     indent = len(first_line) - len(first_line.lstrip(" "))
     # A check comment, indented the appropriate amount
-    # If check_indent is provided, use it; otherwise, auto-detect from MIR body
     if check_indent is not None:
         check = "{}; {}".format(check_indent, prefix)
     else: