diff --git a/llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/generated_funcs_prefix_reuse.ll b/llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/generated_funcs_prefix_reuse.ll
new file mode 100644
--- /dev/null
+++ b/llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/generated_funcs_prefix_reuse.ll
@@ -0,0 +1,37 @@
+; RUN: opt -passes=hotcoldsplit -hotcoldsplit-threshold=0 -S < %s | FileCheck %s --check-prefix=REUSE
+; RUN: opt -passes=hotcoldsplit -hotcoldsplit-threshold=0 -S < %s | FileCheck %s --check-prefix=REUSE
+target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-apple-macosx10.14.0"
+
+@G = external dso_local global i32, align 4
+
+define void @foo(i32) {
+  %2 = icmp eq i32 %0, 0
+  tail call void @_Z10sideeffectv()
+  br i1 %2, label %sink, label %exit
+
+sink:
+  tail call void @_Z10sideeffectv()
+  call void @llvm.trap()
+  unreachable
+
+exit:
+  ret void
+}
+
+define void @bar(i32) {
+  %2 = icmp eq i32 %0, 0
+  tail call void @_Z10sideeffectv()
+  br i1 %2, label %sink, label %exit
+
+sink:
+  tail call void @_Z10sideeffectv()
+  call void @llvm.trap()
+  unreachable
+
+exit:
+  ret void
+}
+
+declare void @llvm.trap() noreturn cold
+declare void @_Z10sideeffectv()
diff --git a/llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/generated_funcs_prefix_reuse.ll.generated.expected b/llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/generated_funcs_prefix_reuse.ll.generated.expected
new file mode 100644
--- /dev/null
+++ b/llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/generated_funcs_prefix_reuse.ll.generated.expected
@@ -0,0 +1,77 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --include-generated-funcs
+; RUN: opt -passes=hotcoldsplit -hotcoldsplit-threshold=0 -S < %s | FileCheck %s --check-prefix=REUSE
+; RUN: opt -passes=hotcoldsplit -hotcoldsplit-threshold=0 -S < %s | FileCheck %s --check-prefix=REUSE
+target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-apple-macosx10.14.0"
+
+@G = external dso_local global i32, align 4
+
+define void @foo(i32) {
+  %2 = icmp eq i32 %0, 0
+  tail call void @_Z10sideeffectv()
+  br i1 %2, label %sink, label %exit
+
+sink:
+  tail call void @_Z10sideeffectv()
+  call void @llvm.trap()
+  unreachable
+
+exit:
+  ret void
+}
+
+define void @bar(i32) {
+  %2 = icmp eq i32 %0, 0
+  tail call void @_Z10sideeffectv()
+  br i1 %2, label %sink, label %exit
+
+sink:
+  tail call void @_Z10sideeffectv()
+  call void @llvm.trap()
+  unreachable
+
+exit:
+  ret void
+}
+
+declare void @llvm.trap() noreturn cold
+declare void @_Z10sideeffectv()
+; REUSE-LABEL: @foo(
+; REUSE-NEXT:    [[TMP2:%.*]] = icmp eq i32 [[TMP0:%.*]], 0
+; REUSE-NEXT:    tail call void @_Z10sideeffectv()
+; REUSE-NEXT:    br i1 [[TMP2]], label [[CODEREPL:%.*]], label [[EXIT:%.*]]
+; REUSE:       codeRepl:
+; REUSE-NEXT:    call void @foo.cold.1() #[[ATTR2:[0-9]+]]
+; REUSE-NEXT:    ret void
+; REUSE:       exit:
+; REUSE-NEXT:    ret void
+;
+;
+; REUSE-LABEL: @bar(
+; REUSE-NEXT:    [[TMP2:%.*]] = icmp eq i32 [[TMP0:%.*]], 0
+; REUSE-NEXT:    tail call void @_Z10sideeffectv()
+; REUSE-NEXT:    br i1 [[TMP2]], label [[CODEREPL:%.*]], label [[EXIT:%.*]]
+; REUSE:       codeRepl:
+; REUSE-NEXT:    call void @bar.cold.1() #[[ATTR2]]
+; REUSE-NEXT:    ret void
+; REUSE:       exit:
+; REUSE-NEXT:    ret void
+;
+;
+; REUSE-LABEL: @foo.cold.1(
+; REUSE-NEXT:  newFuncRoot:
+; REUSE-NEXT:    br label [[SINK:%.*]]
+; REUSE:       sink:
+; REUSE-NEXT:    tail call void @_Z10sideeffectv()
+; REUSE-NEXT:    call void @llvm.trap()
+; REUSE-NEXT:    unreachable
+;
+;
+; REUSE-LABEL: @bar.cold.1(
+; REUSE-NEXT:  newFuncRoot:
+; REUSE-NEXT:    br label [[SINK:%.*]]
+; REUSE:       sink:
+; REUSE-NEXT:    tail call void @_Z10sideeffectv()
+; REUSE-NEXT:    call void @llvm.trap()
+; REUSE-NEXT:    unreachable
+;
diff --git a/llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/generated_funcs_prefix_reuse.ll.generated.globals.expected b/llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/generated_funcs_prefix_reuse.ll.generated.globals.expected
new file mode 100644
--- /dev/null
+++ b/llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/generated_funcs_prefix_reuse.ll.generated.globals.expected
@@ -0,0 +1,85 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --check-globals --include-generated-funcs
+; RUN: opt -passes=hotcoldsplit -hotcoldsplit-threshold=0 -S < %s | FileCheck %s --check-prefix=REUSE
+; RUN: opt -passes=hotcoldsplit -hotcoldsplit-threshold=0 -S < %s | FileCheck %s --check-prefix=REUSE
+target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-apple-macosx10.14.0"
+
+@G = external dso_local global i32, align 4
+
+define void @foo(i32) {
+  %2 = icmp eq i32 %0, 0
+  tail call void @_Z10sideeffectv()
+  br i1 %2, label %sink, label %exit
+
+sink:
+  tail call void @_Z10sideeffectv()
+  call void @llvm.trap()
+  unreachable
+
+exit:
+  ret void
+}
+
+define void @bar(i32) {
+  %2 = icmp eq i32 %0, 0
+  tail call void @_Z10sideeffectv()
+  br i1 %2, label %sink, label %exit
+
+sink:
+  tail call void @_Z10sideeffectv()
+  call void @llvm.trap()
+  unreachable
+
+exit:
+  ret void
+}
+
+declare void @llvm.trap() noreturn cold
+declare void @_Z10sideeffectv()
+;.
+; REUSE: @[[G:[a-zA-Z0-9_$"\\.-]+]] = external dso_local global i32, align 4
+;.
+; REUSE-LABEL: @foo(
+; REUSE-NEXT:    [[TMP2:%.*]] = icmp eq i32 [[TMP0:%.*]], 0
+; REUSE-NEXT:    tail call void @_Z10sideeffectv()
+; REUSE-NEXT:    br i1 [[TMP2]], label [[CODEREPL:%.*]], label [[EXIT:%.*]]
+; REUSE:       codeRepl:
+; REUSE-NEXT:    call void @foo.cold.1() #[[ATTR2:[0-9]+]]
+; REUSE-NEXT:    ret void
+; REUSE:       exit:
+; REUSE-NEXT:    ret void
+;
+;
+; REUSE-LABEL: @bar(
+; REUSE-NEXT:    [[TMP2:%.*]] = icmp eq i32 [[TMP0:%.*]], 0
+; REUSE-NEXT:    tail call void @_Z10sideeffectv()
+; REUSE-NEXT:    br i1 [[TMP2]], label [[CODEREPL:%.*]], label [[EXIT:%.*]]
+; REUSE:       codeRepl:
+; REUSE-NEXT:    call void @bar.cold.1() #[[ATTR2]]
+; REUSE-NEXT:    ret void
+; REUSE:       exit:
+; REUSE-NEXT:    ret void
+;
+;
+; REUSE-LABEL: @foo.cold.1(
+; REUSE-NEXT:  newFuncRoot:
+; REUSE-NEXT:    br label [[SINK:%.*]]
+; REUSE:       sink:
+; REUSE-NEXT:    tail call void @_Z10sideeffectv()
+; REUSE-NEXT:    call void @llvm.trap()
+; REUSE-NEXT:    unreachable
+;
+;
+; REUSE-LABEL: @bar.cold.1(
+; REUSE-NEXT:  newFuncRoot:
+; REUSE-NEXT:    br label [[SINK:%.*]]
+; REUSE:       sink:
+; REUSE-NEXT:    tail call void @_Z10sideeffectv()
+; REUSE-NEXT:    call void @llvm.trap()
+; REUSE-NEXT:    unreachable
+;
+;.
+; REUSE: attributes #[[ATTR0:[0-9]+]] = { cold noreturn nounwind }
+; REUSE: attributes #[[ATTR1:[0-9]+]] = { cold minsize noreturn }
+; REUSE: attributes #[[ATTR2]] = { noinline }
+;.
diff --git a/llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/generated_funcs_prefix_reuse.ll.nogenerated.expected b/llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/generated_funcs_prefix_reuse.ll.nogenerated.expected
new file mode 100644
--- /dev/null
+++ b/llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/generated_funcs_prefix_reuse.ll.nogenerated.expected
@@ -0,0 +1,58 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt -passes=hotcoldsplit -hotcoldsplit-threshold=0 -S < %s | FileCheck %s --check-prefix=REUSE
+; RUN: opt -passes=hotcoldsplit -hotcoldsplit-threshold=0 -S < %s | FileCheck %s --check-prefix=REUSE
+target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-apple-macosx10.14.0"
+
+@G = external dso_local global i32, align 4
+
+define void @foo(i32) {
+; REUSE-LABEL: @foo(
+; REUSE-NEXT:    [[TMP2:%.*]] = icmp eq i32 [[TMP0:%.*]], 0
+; REUSE-NEXT:    tail call void @_Z10sideeffectv()
+; REUSE-NEXT:    br i1 [[TMP2]], label [[CODEREPL:%.*]], label [[EXIT:%.*]]
+; REUSE:       codeRepl:
+; REUSE-NEXT:    call void @foo.cold.1() #[[ATTR2:[0-9]+]]
+; REUSE-NEXT:    ret void
+; REUSE:       exit:
+; REUSE-NEXT:    ret void
+;
+  %2 = icmp eq i32 %0, 0
+  tail call void @_Z10sideeffectv()
+  br i1 %2, label %sink, label %exit
+
+sink:
+  tail call void @_Z10sideeffectv()
+  call void @llvm.trap()
+  unreachable
+
+exit:
+  ret void
+}
+
+define void @bar(i32) {
+; REUSE-LABEL: @bar(
+; REUSE-NEXT:    [[TMP2:%.*]] = icmp eq i32 [[TMP0:%.*]], 0
+; REUSE-NEXT:    tail call void @_Z10sideeffectv()
+; REUSE-NEXT:    br i1 [[TMP2]], label [[CODEREPL:%.*]], label [[EXIT:%.*]]
+; REUSE:       codeRepl:
+; REUSE-NEXT:    call void @bar.cold.1() #[[ATTR2]]
+; REUSE-NEXT:    ret void
+; REUSE:       exit:
+; REUSE-NEXT:    ret void
+;
+  %2 = icmp eq i32 %0, 0
+  tail call void @_Z10sideeffectv()
+  br i1 %2, label %sink, label %exit
+
+sink:
+  tail call void @_Z10sideeffectv()
+  call void @llvm.trap()
+  unreachable
+
+exit:
+  ret void
+}
+
+declare void @llvm.trap() noreturn cold
+declare void @_Z10sideeffectv()
diff --git a/llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/generated_funcs_prefix_reuse.ll.nogenerated.globals.expected b/llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/generated_funcs_prefix_reuse.ll.nogenerated.globals.expected
new file mode 100644
--- /dev/null
+++ b/llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/generated_funcs_prefix_reuse.ll.nogenerated.globals.expected
@@ -0,0 +1,66 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --check-globals
+; RUN: opt -passes=hotcoldsplit -hotcoldsplit-threshold=0 -S < %s | FileCheck %s --check-prefix=REUSE
+; RUN: opt -passes=hotcoldsplit -hotcoldsplit-threshold=0 -S < %s | FileCheck %s --check-prefix=REUSE
+target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-apple-macosx10.14.0"
+
+@G = external dso_local global i32, align 4
+
+;.
+; REUSE: @[[G:[a-zA-Z0-9_$"\\.-]+]] = external dso_local global i32, align 4
+;.
+define void @foo(i32) {
+; REUSE-LABEL: @foo(
+; REUSE-NEXT:    [[TMP2:%.*]] = icmp eq i32 [[TMP0:%.*]], 0
+; REUSE-NEXT:    tail call void @_Z10sideeffectv()
+; REUSE-NEXT:    br i1 [[TMP2]], label [[CODEREPL:%.*]], label [[EXIT:%.*]]
+; REUSE:       codeRepl:
+; REUSE-NEXT:    call void @foo.cold.1() #[[ATTR2:[0-9]+]]
+; REUSE-NEXT:    ret void
+; REUSE:       exit:
+; REUSE-NEXT:    ret void
+;
+  %2 = icmp eq i32 %0, 0
+  tail call void @_Z10sideeffectv()
+  br i1 %2, label %sink, label %exit
+
+sink:
+  tail call void @_Z10sideeffectv()
+  call void @llvm.trap()
+  unreachable
+
+exit:
+  ret void
+}
+
+define void @bar(i32) {
+; REUSE-LABEL: @bar(
+; REUSE-NEXT:    [[TMP2:%.*]] = icmp eq i32 [[TMP0:%.*]], 0
+; REUSE-NEXT:    tail call void @_Z10sideeffectv()
+; REUSE-NEXT:    br i1 [[TMP2]], label [[CODEREPL:%.*]], label [[EXIT:%.*]]
+; REUSE:       codeRepl:
+; REUSE-NEXT:    call void @bar.cold.1() #[[ATTR2]]
+; REUSE-NEXT:    ret void
+; REUSE:       exit:
+; REUSE-NEXT:    ret void
+;
+  %2 = icmp eq i32 %0, 0
+  tail call void @_Z10sideeffectv()
+  br i1 %2, label %sink, label %exit
+
+sink:
+  tail call void @_Z10sideeffectv()
+  call void @llvm.trap()
+  unreachable
+
+exit:
+  ret void
+}
+
+declare void @llvm.trap() noreturn cold
+declare void @_Z10sideeffectv()
+;.
+; REUSE: attributes #[[ATTR0:[0-9]+]] = { cold noreturn nounwind }
+; REUSE: attributes #[[ATTR1:[0-9]+]] = { cold minsize noreturn }
+; REUSE: attributes #[[ATTR2]] = { noinline }
+;.
diff --git a/llvm/test/tools/UpdateTestChecks/update_test_checks/generated_funcs_prefix_reuse.test b/llvm/test/tools/UpdateTestChecks/update_test_checks/generated_funcs_prefix_reuse.test
new file mode 100644
--- /dev/null
+++ b/llvm/test/tools/UpdateTestChecks/update_test_checks/generated_funcs_prefix_reuse.test
@@ -0,0 +1,21 @@
+## Check that generated functions are included.
+# RUN: cp -f %S/Inputs/generated_funcs_prefix_reuse.ll %t.ll && %update_test_checks --include-generated-funcs %t.ll
+# RUN: diff -u %t.ll %S/Inputs/generated_funcs_prefix_reuse.ll.generated.expected
+
+## Check that running the script again does not change the result:
+# RUN: %update_test_checks --include-generated-funcs %t.ll
+# RUN: diff -u %t.ll %S/Inputs/generated_funcs_prefix_reuse.ll.generated.expected
+## Also try the --check-globals flag
+# RUN: %update_test_checks %t.ll --check-globals
+# RUN: diff -u %t.ll %S/Inputs/generated_funcs_prefix_reuse.ll.generated.globals.expected
+
+## Check that generated functions are not included.
+# RUN: cp -f %S/Inputs/generated_funcs_prefix_reuse.ll %t.ll && %update_test_checks %t.ll
+# RUN: diff -u %t.ll %S/Inputs/generated_funcs_prefix_reuse.ll.nogenerated.expected
+
+## Check that running the script again does not change the result:
+# RUN: %update_test_checks %t.ll
+# RUN: diff -u %t.ll %S/Inputs/generated_funcs_prefix_reuse.ll.nogenerated.expected
+## Also try the --check-globals flag
+# RUN: %update_test_checks %t.ll --check-globals
+# RUN: diff -u %t.ll %S/Inputs/generated_funcs_prefix_reuse.ll.nogenerated.globals.expected
diff --git a/llvm/utils/UpdateTestChecks/common.py b/llvm/utils/UpdateTestChecks/common.py
--- a/llvm/utils/UpdateTestChecks/common.py
+++ b/llvm/utils/UpdateTestChecks/common.py
@@ -1221,15 +1221,18 @@
 def add_checks_at_end(output_lines, prefix_list, func_order,
                       comment_string, check_generator):
   added = set()
-  generated_prefixes = []
+  generated_prefixes = set()
   for prefix in prefix_list:
     prefixes = prefix[0]
     tool_args = prefix[1]
     for prefix in prefixes:
       for func in func_order[prefix]:
+        # The func order can contain the same functions multiple times.
+        # If we see one again we are done.
+        if (func, prefix) in added:
+            continue
         if added:
           output_lines.append(comment_string)
-        added.add(func)
 
         # The add_*_checks routines expect a run list whose items are
         # tuples that have a list of prefixes as their first element and
@@ -1245,7 +1248,8 @@
         # single prefix before moving on to the next prefix.  So checks
         # are ordered by prefix instead of by function as in "normal"
         # mode.
-        generated_prefixes.extend(check_generator(output_lines,
-                        [([prefix], tool_args)],
-                        func))
+        for generated_prefix in check_generator(output_lines,
+                        [([prefix], tool_args)], func):
+            added.add((func, generated_prefix))
+            generated_prefixes.add(generated_prefix)
   return generated_prefixes