[Utils][FIX] Properly deal with occasionally deleted functions

[jdoerfert]

Summary

While D68850 allowed functions to be deleted I accidentally saved some
version of the function to be used once a suitable prefix was found.
This turned out to be problematic when the occasionally deleted function
is also occasionally modified. The test case is adjusted to resemble the
case in which the problem was found.

[lebedev.ri]

Seems reasonable to me.

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

-; RUN: opt -S < %s | FileCheck %s --check-prefixes=ALL,FIRST
-; RUN: opt -S -globalopt < %s | FileCheck %s --check-prefixes=ALL,SECOND
+; RUN: opt -S < %s | FileCheck %s --check-prefixes=ALL,ALL_BUT_TWO,ALL_BUT_THREE,ALL_BUT_FOUR,ONE_AND_TWO,ONE_AND_THREE,ONE_AND_FOUR,ONE
+; RUN: opt -S -globalopt < %s | FileCheck %s --check-prefixes=ALL,ALL_BUT_ONE,ALL_BUT_THREE,ALL_BUT_FOUR,ONE_AND_TWO,TWO_AND_THREE,TWO_AND_FOUR,TWO
+; RUN: opt -S -instsimplify < %s | FileCheck %s --check-prefixes=ALL,ALL_BUT_ONE,ALL_BUT_TWO,ALL_BUT_FOUR,ONE_AND_THREE,TWO_AND_THREE,THREE_AND_FOUR,THREE
+; RUN: opt -S < %s | FileCheck %s --check-prefixes=ALL,ALL_BUT_ONE,ALL_BUT_TWO,ALL_BUT_THREE,ONE_AND_FOUR,TWO_AND_FOUR,THREE_AND_FOUR,FOUR
 ;
-; Make sure we use FIRST to check for @sometimes_here as ALL does not work.
+; Make sure we don't use anything to check for @sometimes_here that contains "ALL" or "TWO".
+; Also verify we use "ONE_AND_FOUR" for the unmodified @sometimes_here version and "THREE" for the version without the add.
 
 define internal void @sometimes_here() {
+  %c = add i32 undef, undef
   ret void
 }
 
 define void @always_here() {
   ret void
 }

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

 ; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
-; RUN: opt -S < %s | FileCheck %s --check-prefixes=ALL,FIRST
-; RUN: opt -S -globalopt < %s | FileCheck %s --check-prefixes=ALL,SECOND
+; RUN: opt -S < %s | FileCheck %s --check-prefixes=ALL,ALL_BUT_TWO,ALL_BUT_THREE,ALL_BUT_FOUR,ONE_AND_TWO,ONE_AND_THREE,ONE_AND_FOUR,ONE
+; RUN: opt -S -globalopt < %s | FileCheck %s --check-prefixes=ALL,ALL_BUT_ONE,ALL_BUT_THREE,ALL_BUT_FOUR,ONE_AND_TWO,TWO_AND_THREE,TWO_AND_FOUR,TWO
+; RUN: opt -S -instsimplify < %s | FileCheck %s --check-prefixes=ALL,ALL_BUT_ONE,ALL_BUT_TWO,ALL_BUT_FOUR,ONE_AND_THREE,TWO_AND_THREE,THREE_AND_FOUR,THREE
+; RUN: opt -S < %s | FileCheck %s --check-prefixes=ALL,ALL_BUT_ONE,ALL_BUT_TWO,ALL_BUT_THREE,ONE_AND_FOUR,TWO_AND_FOUR,THREE_AND_FOUR,FOUR
 ;
-; Make sure we use FIRST to check for @sometimes_here as ALL does not work.
+; Make sure we don't use anything to check for @sometimes_here that contains "ALL" or "TWO".
+; Also verify we use "ONE_AND_FOUR" for the unmodified @sometimes_here version and "THREE" for the version without the add.
 
 define internal void @sometimes_here() {
-; FIRST-LABEL: @sometimes_here(
-; FIRST-NEXT:    ret void
+; ONE_AND_FOUR-LABEL: @sometimes_here(
+; ONE_AND_FOUR-NEXT:    [[C:%.*]] = add i32 undef, undef
+; ONE_AND_FOUR-NEXT:    ret void
 ;
+; THREE-LABEL: @sometimes_here(
+; THREE-NEXT:    ret void
+;
+  %c = add i32 undef, undef
   ret void
 }
 
 define void @always_here() {
 ; ALL-LABEL: @always_here(
 ; ALL-NEXT:    ret void
 ;
   ret void
 }

llvm/utils/UpdateTestChecks/common.py

for p in prefix_list:
     # other run lines created it.
     if any(map(lambda checkprefix: func_name not in func_dict[checkprefix], checkprefixes)):
         prefix_blacklist |= set(checkprefixes)
         continue
 
   # prefix_blacklist is constructed, we can now emit the output
   for p in prefix_list:
     checkprefixes = p[0]
-    saved_output = None
     for checkprefix in checkprefixes:
       if checkprefix in printed_prefixes:
         break
 
-      # prefix is blacklisted. We remember the output as we might need it later but we will not emit anything for the prefix.
+      # Check if the prefix is blacklisted.
       if checkprefix in prefix_blacklist:
-          if not saved_output and func_name in func_dict[checkprefix]:
-              saved_output = func_dict[checkprefix][func_name]
-          continue
 
-      # If we do not have output for this prefix but there is one saved, we go ahead with this prefix and the saved output.
+      # If we do not have output for this prefix we skip it.
       if not func_dict[checkprefix][func_name]:
-        if not saved_output:
-            continue
-        func_dict[checkprefix][func_name] = saved_output
 
       # Add some space between different check prefixes, but not after the last
       # check line (before the test code).
       if is_asm:
         if len(printed_prefixes) != 0:
           output_lines.append(comment_marker)
 
       vars_seen = set()