[update_test_checks] Default to --function-signature for new tests

[arichardson]

Summary

As was recently brought up in D139006, not using --function-signature by
default can cause tests to fail unexpectedly due to not matching "define"
in the function declaration. The referenced review tried to fix this but
was ultimately reverted due to the test churn that it causes.

This is an alternative approach, suggested by @nikic in D139006 that
defaults to --function-signature for new tests but keeps existing ones
unchanged. The implementation is somewhat ugly, using magic constants
for the --function-signature flag default values, but I can't see a way of
avoiding this.

[asb]

Some general thoughts:

Although I understand the concerns about churn from updating auto-generated tests, I was concerned that an approach like this might have greater disadvantages than just landing a patch that regenerates everything (after all, churn in auto-generated tests has far fewer practical issues vs e.g. clang-formatting - conflicts are easily resolved by regenerating).

Though looking through the implementation, it doesn't seem overly complicated and seems like a sensible path forwards. I wouldn't be supportive of using such an approach for all future behaviour changes though - the complexity would just accrete and it makes the behaviour of the tool harder to predict.

[arichardson]

In D140212#4007438, @asb wrote:

Some general thoughts:

Although I understand the concerns about churn from updating auto-generated tests, I was concerned that an approach like this might have greater disadvantages than just landing a patch that regenerates everything (after all, churn in auto-generated tests has far fewer practical issues vs e.g. clang-formatting - conflicts are easily resolved by regenerating).

Though looking through the implementation, it doesn't seem overly complicated and seems like a sensible path forwards. I wouldn't be supportive of using such an approach for all future behaviour changes though - the complexity would just accrete and it makes the behaviour of the tool harder to predict.

I'm hoping that if we can land this, we can eventually upgrade all autogenerated tests without a function signature to use it and once that has happened, remove this workaround. I can see that there are still lots of new tests being added that don't use --function-signature and this will continue until --function-signature is the default.

[nikic]

In D140212#4007438, @asb wrote:

Some general thoughts:

Although I understand the concerns about churn from updating auto-generated tests, I was concerned that an approach like this might have greater disadvantages than just landing a patch that regenerates everything (after all, churn in auto-generated tests has far fewer practical issues vs e.g. clang-formatting - conflicts are easily resolved by regenerating).

For this change this would require regenerating close to 5000 tests. Not out of the question, but it's a bit more than the usual amount of churn.

Anyway, I think before making this change we should probably land D133943 first. Doing that change will be harder if --function-signature is more widely used. (Alternatively, if we introduce a --version flag as I suggested before, we could do that as a separate version bump without test regeneration.)

[nikic]

Superseded by D145149.

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

+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
 ; RUN: opt < %s -S | FileCheck %s
 
 define i32 @reuse_arg_names(i32 %X, i32 %Y) {
   %Z = sub i32 %X, %Y
   %Q = add i32 %Z, %Y
   ret i32 %Q
 }

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

-; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --function-signature
 ; Example input for update_test_checks (taken from test/Transforms/InstSimplify/add.ll)
 ; RUN: opt < %s -passes=instsimplify -S | FileCheck %s
 
 define i32 @common_sub_operand(i32 %X, i32 %Y) {
-; CHECK-LABEL: @common_sub_operand(
-; CHECK-NEXT:    ret i32 [[X:%.*]]
+; CHECK-LABEL: define {{[^@]+}}@common_sub_operand
+; CHECK-SAME: (i32 [[X:%.*]], i32 [[Y:%.*]]) {
+; CHECK-NEXT:    ret i32 [[X]]
 ;
   %Z = sub i32 %X, %Y
   %Q = add i32 %Z, %Y
   ret i32 %Q
 }
 
 define i32 @negated_operand(i32 %x) {
-; CHECK-LABEL: @negated_operand(
+; CHECK-LABEL: define {{[^@]+}}@negated_operand
+; CHECK-SAME: (i32 [[X:%.*]]) {
 ; CHECK-NEXT:    ret i32 0
 ;
   %negx = sub i32 0, %x
   %r = add i32 %negx, %x
   ret i32 %r
 }
 
 define <2 x i32> @negated_operand_commute_vec(<2 x i32> %x) {
-; CHECK-LABEL: @negated_operand_commute_vec(
+; CHECK-LABEL: define {{[^@]+}}@negated_operand_commute_vec
+; CHECK-SAME: (<2 x i32> [[X:%.*]]) {
 ; CHECK-NEXT:    ret <2 x i32> zeroinitializer
 ;
   %negx = sub <2 x i32> zeroinitializer, %x
   %r = add <2 x i32> %x, %negx
   ret <2 x i32> %r
 }
 
 define i8 @knownnegation(i8 %x, i8 %y) {
-; CHECK-LABEL: @knownnegation(
+; CHECK-LABEL: define {{[^@]+}}@knownnegation
+; CHECK-SAME: (i8 [[X:%.*]], i8 [[Y:%.*]]) {
 ; CHECK-NEXT:    ret i8 0
 ;
   %xy = sub i8 %x, %y
   %yx = sub i8 %y, %x
   %r = add i8 %xy, %yx
   ret i8 %r
 }
 
 define <2 x i8> @knownnegation_commute_vec(<2 x i8> %x, <2 x i8> %y) {
-; CHECK-LABEL: @knownnegation_commute_vec(
+; CHECK-LABEL: define {{[^@]+}}@knownnegation_commute_vec
+; CHECK-SAME: (<2 x i8> [[X:%.*]], <2 x i8> [[Y:%.*]]) {
 ; CHECK-NEXT:    ret <2 x i8> zeroinitializer
 ;
   %xy = sub <2 x i8> %x, %y
   %yx = sub <2 x i8> %y, %x
   %r = add <2 x i8> %yx, %xy
   ret <2 x i8> %r
 }
 
 define i32 @nameless_value(i32 %X) {
-; CHECK-LABEL: @nameless_value(
-; CHECK-NEXT:    [[TMP1:%.*]] = sub i32 42, [[X:%.*]]
+; CHECK-LABEL: define {{[^@]+}}@nameless_value
+; CHECK-SAME: (i32 [[X:%.*]]) {
+; CHECK-NEXT:    [[TMP1:%.*]] = sub i32 42, [[X]]
 ; CHECK-NEXT:    ret i32 [[TMP1]]
 ;
   %1 = sub i32 42, %X
   ret i32 %1
 }

llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/basic.ll.funcsig.expected

-; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --function-signature
-; Example input for update_test_checks (taken from test/Transforms/InstSimplify/add.ll)
-; RUN: opt < %s -passes=instsimplify -S | FileCheck %s
-
-define i32 @common_sub_operand(i32 %X, i32 %Y) {
-; CHECK-LABEL: define {{[^@]+}}@common_sub_operand
-; CHECK-SAME: (i32 [[X:%.*]], i32 [[Y:%.*]]) {
-; CHECK-NEXT:    ret i32 [[X]]
-;
-  %Z = sub i32 %X, %Y
-  %Q = add i32 %Z, %Y
-  ret i32 %Q
-}
-
-define i32 @negated_operand(i32 %x) {
-; CHECK-LABEL: define {{[^@]+}}@negated_operand
-; CHECK-SAME: (i32 [[X:%.*]]) {
-; CHECK-NEXT:    ret i32 0
-;
-  %negx = sub i32 0, %x
-  %r = add i32 %negx, %x
-  ret i32 %r
-}
-
-define <2 x i32> @negated_operand_commute_vec(<2 x i32> %x) {
-; CHECK-LABEL: define {{[^@]+}}@negated_operand_commute_vec
-; CHECK-SAME: (<2 x i32> [[X:%.*]]) {
-; CHECK-NEXT:    ret <2 x i32> zeroinitializer
-;
-  %negx = sub <2 x i32> zeroinitializer, %x
-  %r = add <2 x i32> %x, %negx
-  ret <2 x i32> %r
-}
-
-define i8 @knownnegation(i8 %x, i8 %y) {
-; CHECK-LABEL: define {{[^@]+}}@knownnegation
-; CHECK-SAME: (i8 [[X:%.*]], i8 [[Y:%.*]]) {
-; CHECK-NEXT:    ret i8 0
-;
-  %xy = sub i8 %x, %y
-  %yx = sub i8 %y, %x
-  %r = add i8 %xy, %yx
-  ret i8 %r
-}
-
-define <2 x i8> @knownnegation_commute_vec(<2 x i8> %x, <2 x i8> %y) {
-; CHECK-LABEL: define {{[^@]+}}@knownnegation_commute_vec
-; CHECK-SAME: (<2 x i8> [[X:%.*]], <2 x i8> [[Y:%.*]]) {
-; CHECK-NEXT:    ret <2 x i8> zeroinitializer
-;
-  %xy = sub <2 x i8> %x, %y
-  %yx = sub <2 x i8> %y, %x
-  %r = add <2 x i8> %yx, %xy
-  ret <2 x i8> %r
-}
-
-define i32 @nameless_value(i32 %X) {
-; CHECK-LABEL: define {{[^@]+}}@nameless_value
-; CHECK-SAME: (i32 [[X:%.*]]) {
-; CHECK-NEXT:    [[TMP1:%.*]] = sub i32 42, [[X]]
-; CHECK-NEXT:    ret i32 [[TMP1]]
-;
-  %1 = sub i32 42, %X
-  ret i32 %1
-}

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

+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
 ; RUN: opt -aa-pipeline=basic-aa -passes=attributor -S < %s | FileCheck %s --check-prefixes=CHECK,IS__TUNIT____
 ; RUN: opt -aa-pipeline=basic-aa -passes=attributor-cgscc -S < %s | FileCheck %s --check-prefixes=CHECK,IS__CGSCC____
 
 %struct.RT = type { i8, [10 x [20 x i32]], i8 }
 %struct.ST = type { i32, double, %struct.RT }
 
 define i32* @foo(%struct.ST* %s) nounwind uwtable readnone optsize ssp {
 entry:
   %arrayidx = getelementptr inbounds %struct.ST, %struct.ST* %s, i64 1, i32 2, i32 1, i64 5, i64 13
   ret i32* %arrayidx
 }

llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/check_attrs.ll.funcattrs.expected

-; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --function-signature --check-attributes
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --check-attributes --function-signature
 ; RUN: opt -aa-pipeline=basic-aa -passes=attributor -S < %s | FileCheck %s --check-prefixes=CHECK,IS__TUNIT____
 ; RUN: opt -aa-pipeline=basic-aa -passes=attributor-cgscc -S < %s | FileCheck %s --check-prefixes=CHECK,IS__CGSCC____
 
 %struct.RT = type { i8, [10 x [20 x i32]], i8 }
 %struct.ST = type { i32, double, %struct.RT }
 
 define i32* @foo(%struct.ST* %s) nounwind uwtable readnone optsize ssp {
 ; CHECK: Function Attrs: nofree norecurse nosync nounwind optsize ssp willreturn memory(none) uwtable

llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/custom-tool.ll.expected

-; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --tool llvm-extract
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --tool llvm-extract --function-signature
 ; RUN: llvm-extract -S --func=foo %s | FileCheck --check-prefixes=CHECK %s
 
 define i32 @foo(i32 %x) {
-; CHECK-LABEL: @foo(
-; CHECK-NEXT:    [[Y:%.*]] = add i32 [[X:%.*]], 1
+; CHECK-LABEL: define {{[^@]+}}@foo
+; CHECK-SAME: (i32 [[X:%.*]]) {
+; CHECK-NEXT:    [[Y:%.*]] = add i32 [[X]], 1
 ; CHECK-NEXT:    ret i32 [[Y]]
 ;
   %y = add i32 %x, 1
   ret i32 %y
 }

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

-; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --function-signature
 ; Check that we accept functions with '$' in the name.
 ;
 ; RUN: opt < %s -passes=instsimplify -S | FileCheck %s
 ;
 define hidden i32 @"_Z54bar$ompvariant$bar"() {
 entry:
   ret i32 2
 }
 ;; NOTE: These prefixes are unused and the list is autogenerated. Do not add tests below this line:
 ; CHECK: {{.*}}

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

+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
 ; RUN: opt -passes=hotcoldsplit -hotcoldsplit-threshold=0 -S < %s | FileCheck %s
 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

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

+; 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) {

llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/no-funcsig-for-existing-note.ll

+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; This test already has a autogenerated note, so we should not default to
+; adding function signature matches since that would cause lots of test churn.
+; RUN: opt < %s -passes=instsimplify -S | FileCheck %s
+
+define i32 @common_sub_operand(i32 %X, i32 %Y) {
+; CHECK-LABEL: @common_sub_operand(
+; CHECK-NEXT:    ret i32 [[X:%.*]]
+;
+  %Z = sub i32 %X, %Y
+  %Q = add i32 %Z, %Y
+  ret i32 %Q
+}

llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/no-funcsig-for-existing-note.ll.expected-with-flag

+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --function-signature
+; This test already has a autogenerated note, so we should not default to
+; adding function signature matches since that would cause lots of test churn.
+; RUN: opt < %s -passes=instsimplify -S | FileCheck %s
+
+define i32 @common_sub_operand(i32 %X, i32 %Y) {
+; CHECK-LABEL: define {{[^@]+}}@common_sub_operand
+; CHECK-SAME: (i32 [[X:%.*]], i32 [[Y:%.*]]) {
+; CHECK-NEXT:    ret i32 [[X]]
+;
+  %Z = sub i32 %X, %Y
+  %Q = add i32 %Z, %Y
+  ret i32 %Q
+}

llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/no-funcsig-for-existing-note.ll.expected-with-negative-flag

+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --no-function-signature
+; This test already has a autogenerated note, so we should not default to
+; adding function signature matches since that would cause lots of test churn.
+; RUN: opt < %s -passes=instsimplify -S | FileCheck %s
+
+define i32 @common_sub_operand(i32 %X, i32 %Y) {
+; CHECK-LABEL: @common_sub_operand(
+; CHECK-NEXT:    ret i32 [[X:%.*]]
+;
+  %Z = sub i32 %X, %Y
+  %Q = add i32 %Z, %Y
+  ret i32 %Q
+}

llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/no-funcsig-for-existing-note.ll.expected-with-unrelated-flag

+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --scrub-attributes
+; This test already has a autogenerated note, so we should not default to
+; adding function signature matches since that would cause lots of test churn.
+; RUN: opt < %s -passes=instsimplify -S | FileCheck %s
+
+define i32 @common_sub_operand(i32 %X, i32 %Y) {
+; CHECK-LABEL: @common_sub_operand(
+; CHECK-NEXT:    ret i32 [[X:%.*]]
+;
+  %Z = sub i32 %X, %Y
+  %Q = add i32 %Z, %Y
+  ret i32 %Q
+}

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

-; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --function-signature --scrub-attributes
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --scrub-attributes --function-signature
 ; RUN: opt -S < %s | FileCheck %s
 
 declare void @foo()
 
 define void @check_lines_1() {
 ; CHECK-LABEL: define {{[^@]+}}@check_lines_1() {
 ; CHECK-NEXT:    ret void
 ;

llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/on_the_fly_arg_change.ll.initially_disabled.expected

-; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --function-signature --scrub-attributes --disable
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --scrub-attributes --disable --function-signature
 ; RUN: opt -S < %s | FileCheck %s
 
 declare void @foo()
 
 define void @check_lines_1() {
   ret void
 }
 

llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/prefix-never-matches.ll.expected

-; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --function-signature
 ; RUN: opt -O0 -S < %s  | FileCheck %s -check-prefix=A
 ; RUN: opt -O3 -S < %s  | FileCheck %s -check-prefix=A
 
 define i32 @foo(i32 %i) {
   %r = add i32 1, 1
   ret i32 %r
 }
 ;; NOTE: These prefixes are unused and the list is autogenerated. Do not add tests below this line:
 ; A: {{.*}}

llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/scrub_attrs.ll.plain.expected

-; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --function-signature
 ; RUN: opt -S < %s | FileCheck %s
 
 declare void @foo()
 
 define internal void @bar() {
-; CHECK-LABEL: @bar(
+; CHECK-LABEL: define {{[^@]+}}@bar() {
 ; CHECK-NEXT:    call void @foo() #[[ATTR0:[0-9]+]]
 ; CHECK-NEXT:    ret void
 ;
   call void @foo() readnone
   ret void
 }

llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/scrub_attrs.ll.scrub.expected

-; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --scrub-attributes
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --scrub-attributes --function-signature
 ; RUN: opt -S < %s | FileCheck %s
 
 declare void @foo()
 
 define internal void @bar() {
-; CHECK-LABEL: @bar(
+; CHECK-LABEL: define {{[^@]+}}@bar() {
 ; CHECK-NEXT:    call void @foo()
 ; CHECK-NEXT:    ret void
 ;
   call void @foo() readnone
   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
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --function-signature
 ; 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 -passes=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 -passes=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 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() {
-; ONE_AND_FOUR-LABEL: @sometimes_here(
+; ONE_AND_FOUR-LABEL: define {{[^@]+}}@sometimes_here() {
 ; ONE_AND_FOUR-NEXT:    [[C:%.*]] = add i32 undef, undef
 ; ONE_AND_FOUR-NEXT:    ret void
 ;
-; THREE-LABEL: @sometimes_here(
+; THREE-LABEL: define {{[^@]+}}@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
+; ALL_BUT_TWO-LABEL: define {{[^@]+}}@always_here() {
+; ALL_BUT_TWO-NEXT:    ret void
+;
+; TWO-LABEL: define {{[^@]+}}@always_here() local_unnamed_addr {
+; TWO-NEXT:    ret void
 ;
   ret void
 }
 ;; NOTE: These prefixes are unused and the list is autogenerated. Do not add tests below this line:
+; ALL: {{.*}}
 ; ALL_BUT_FOUR: {{.*}}
 ; ALL_BUT_ONE: {{.*}}
 ; ALL_BUT_THREE: {{.*}}
-; ALL_BUT_TWO: {{.*}}
 ; FOUR: {{.*}}
 ; ONE: {{.*}}
 ; ONE_AND_THREE: {{.*}}
 ; ONE_AND_TWO: {{.*}}
 ; THREE_AND_FOUR: {{.*}}
-; TWO: {{.*}}
 ; TWO_AND_FOUR: {{.*}}
 ; TWO_AND_THREE: {{.*}}

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

+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
 ; Just run it through opt, no passes needed.
 ; RUN: opt < %s -S | FileCheck %s
 
 ; ModuleID = 'various_ir_values.c'
 source_filename = "various_ir_values.c"
 target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
 target triple = "x86_64-unknown-linux-gnu"
 

llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/various_ir_values.ll.funcsig.globals.expected

-; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --function-signature --check-globals
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --check-globals --function-signature
 ; Just run it through opt, no passes needed.
 ; RUN: opt < %s -S | FileCheck %s
 
 ; ModuleID = 'various_ir_values.c'
 source_filename = "various_ir_values.c"
 target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
 target triple = "x86_64-unknown-linux-gnu"
 

llvm/test/tools/UpdateTestChecks/update_test_checks/basic.test

 # REQUIRES: x86-registered-target
 ## Basic test checking that update_test_checks.py works correctly
 # RUN: cp -f %S/Inputs/basic.ll %t.ll && %update_test_checks %t.ll
 # RUN: diff -u %t.ll %S/Inputs/basic.ll.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/basic.ll.expected
-## Also try the --function-signature flag
-# RUN: %update_test_checks %t.ll --function-signature
-# RUN: diff -u %t.ll %S/Inputs/basic.ll.funcsig.expected
-## Verify that running without the --function-signature flag does not removes
-## the -SAME: lines since the generated file will have --function-signature in
-## an UTC_ARGS: comment in the first line (from the invocation above) which is
-## added to the update invocation below.
-# RUN: %update_test_checks %t.ll
-# RUN: diff -u %t.ll %S/Inputs/basic.ll.funcsig.expected

llvm/test/tools/UpdateTestChecks/update_test_checks/no-funcsig-for-existing-note.test

+# REQUIRES: x86-registered-target
+## Check that we do not add function signature matches for tests that already
+## have an autogeneration note since that would cause lots of test churn.
+# RUN: cp -f %S/Inputs/no-funcsig-for-existing-note.ll %t.ll && %update_test_checks %t.ll
+# RUN: diff -u %t.ll %S/Inputs/no-funcsig-for-existing-note.ll
+## Check that running the script again does not change the result:
+# RUN: %update_test_checks %t.ll
+# RUN: diff -u %t.ll %S/Inputs/no-funcsig-for-existing-note.ll
+## Adding an explicit --function-signature flag should add the lines though:
+# RUN: %update_test_checks %t.ll --function-signature
+# RUN: diff -u %t.ll %S/Inputs/no-funcsig-for-existing-note.ll.expected-with-flag
+## Running the script without arguments again should keep the function signature
+# RUN: %update_test_checks %t.ll
+# RUN: diff -u %t.ll %S/Inputs/no-funcsig-for-existing-note.ll.expected-with-flag
+
+## Check that an unrelated flag in UTC_ARGS does not implicitly enable --function-signature
+# RUN: cp -f %S/Inputs/no-funcsig-for-existing-note.ll.expected-with-unrelated-flag %t.ll && %update_test_checks %t.ll
+# RUN: diff -u %t.ll %S/Inputs/no-funcsig-for-existing-note.ll.expected-with-unrelated-flag
+
+## Check that --function-signature is included in UTC_ARGS for newly generated check lines
+# RUN: sed '1d' %S/Inputs/no-funcsig-for-existing-note.ll > %t.ll
+# RUN: %update_test_checks %t.ll --update-only 2>&1 | FileCheck %s --check-prefix=SKIP
+# SKIP: Skipping test which isn't autogenerated: {{.+}}.ll
+# RUN: %update_test_checks %t.ll
+# RUN: diff -u %t.ll %S/Inputs/no-funcsig-for-existing-note.ll.expected-with-flag
+
+## Finally also check --no-function-signature
+# RUN: cp -f %S/Inputs/no-funcsig-for-existing-note.ll %t.ll && %update_test_checks %t.ll --no-function-signature
+# RUN: diff -u %t.ll %S/Inputs/no-funcsig-for-existing-note.ll.expected-with-negative-flag
+## --no-function-signature on the command line does not override the value in UTC_ARGS:
+# RUN: cp -f %S/Inputs/no-funcsig-for-existing-note.ll.expected-with-flag %t.ll && %update_test_checks %t.ll --no-function-signature
+# RUN: diff -u %t.ll %S/Inputs/no-funcsig-for-existing-note.ll.expected-with-flag

llvm/utils/UpdateTestChecks/common.py

def __init__(self, regex, is_filter_out):
     super(Filter, self).__init__(regex)
     self.is_filter_out = is_filter_out
 
   def __deepcopy__(self, memo):
     result = copy.deepcopy(super(Filter, self), memo)
     result.is_filter_out = copy.deepcopy(self.is_filter_out, memo)
     return result
 
-def parse_commandline_args(parser):
+# We set the default value for --function-signature to 2 which evaluates to True
+# in a boolean context, but we use this magic number to ensure that the value
+# is actually only set to True for new tests or tests that contain it in
+# UTC_ARGS (see itertests). This is needed to avoid lots of test churn.
+_FUNCSIG_ARGUMENT_DEFAULT_VALUE = 2
+_FUNCSIG_ARGUMENT_NO_VALUE = None
+
+def parse_commandline_args(parser, *, add_funcsig_flag=False):
   class RegexAction(argparse.Action):
     """Add a regular expression option value to a list of regular expressions.
     This compiles the expression, wraps it in a Regex and adds it to the option
     value list."""
     def __init__(self, option_strings, dest, nargs=None, **kwargs):
       if nargs is not None:
         raise ValueError('nargs not allowed')
       super(RegexAction, self).__init__(option_strings, dest, **kwargs)
parser.add_argument('--global-hex-value-regex', nargs='+', default=[],
                       help='List of regular expressions such that, for matching global value declarations, literal integer values should be encoded in hex in the associated FileCheck directives')
   # FIXME: in 3.9, we can use argparse.BooleanOptionalAction. At that point,
   # we need to rename the flag to just -generate-body-for-unused-prefixes.
   parser.add_argument('--no-generate-body-for-unused-prefixes',
                       action='store_false',
                       dest='gen_unused_prefix_body',
                       default=True,
                       help='Generate a function body that always matches for unused prefixes. This is useful when unused prefixes are desired, and it avoids needing to annotate each FileCheck as allowing them.')
+  if add_funcsig_flag:
+    parser.add_argument('--function-signature', action='store_true',
+                        default=_FUNCSIG_ARGUMENT_DEFAULT_VALUE,
+                        help='Keep function signature information around for the check line')
+    parser.add_argument('--no-function-signature', action='store_false',
+                        dest="function_signature",
+                        help='Do not keep function signature information around for the check line')
   args = parser.parse_args()
   global _verbose, _global_value_regex, _global_hex_value_regex
   _verbose = args.verbose
   _global_value_regex = args.global_value_regex
   _global_hex_value_regex = args.global_hex_value_regex
   return args
 
 
for test in tests_list:
       if argparse_callback is not None:
         argparse_callback(args)
       argv = sys.argv[:]
       first_line = input_lines[0] if input_lines else ""
       if UTC_ADVERT in first_line:
         if script_name not in first_line and not args.force_update:
           warn("Skipping test which wasn't autogenerated by " + script_name, test)
           continue
+        # The following if statement is a workaround to avoid major test churn
+        # by only enabling --function-signature by default for new test but not
+        # tests with existing check lines.
         args, argv = check_for_command(first_line, parser, args, argv, argparse_callback)
+        if getattr(args, "function_signature", None) == _FUNCSIG_ARGUMENT_DEFAULT_VALUE:
+          # NB: not False to avoid modifying UTC_ARGS
+          args.function_signature = _FUNCSIG_ARGUMENT_NO_VALUE
       elif args.update_only:
         assert UTC_ADVERT not in first_line
         warn("Skipping test which isn't autogenerated: " + test)
         continue
       final_input_lines = []
       for l in input_lines:
         if UNUSED_NOTE in l:
           break
def get_autogennote_suffix(parser, args):
   for action in parser._actions:
     if not hasattr(args, action.dest):
       continue  # Ignore options such as --help that aren't included in args
     # Ignore parameters such as paths to the binary or the list of tests
     if action.dest in ('tests', 'update_only', 'tool_binary', 'opt_binary',
                        'llc_binary', 'clang', 'opt', 'llvm_bin', 'verbose'):
       continue
     value = getattr(args, action.dest)
+    if action.dest == 'function_signature':
+      if value is _FUNCSIG_ARGUMENT_NO_VALUE:
+        continue  # Don't add --no-function-signature to existing tests
+      if value is _FUNCSIG_ARGUMENT_DEFAULT_VALUE:
+        value = True  # Ensure we add --function-signature to new tests.
     if action.const is not None:  # action stores a constant (usually True/False)
       # Skip actions with different constant values (this happens with boolean
       # --foo/--no-foo options)
       if value != action.const:
         continue
     if parser.get_default(action.dest) == value:
       continue  # Don't add default values
     if action.dest == 'filters':

llvm/utils/update_test_checks.py

def main():
   parser.add_argument('--tool', default='opt',
                       help='The name of the tool used to generate the test case (defaults to "opt")')
   parser.add_argument('--tool-binary', '--opt-binary',
                       help='The tool binary used to generate the test case')
   parser.add_argument(
       '--function', help='The function in the test file to update')
   parser.add_argument('-p', '--preserve-names', action='store_true',
                       help='Do not scrub IR names')
-  parser.add_argument('--function-signature', action='store_true',
-                      help='Keep function signature information around for the check line')
   parser.add_argument('--scrub-attributes', action='store_true',
                       help='Remove attribute annotations (#0) from the end of check line')
   parser.add_argument('--check-attributes', action='store_true',
                       help='Check "Function Attributes" for functions')
   parser.add_argument('--check-globals', action='store_true',
                       help='Check global entries (global variables, metadata, attribute sets, ...) for functions')
   parser.add_argument('tests', nargs='+')
-  initial_args = common.parse_commandline_args(parser)
+  initial_args = common.parse_commandline_args(parser, add_funcsig_flag=True)
 
   script_name = os.path.basename(__file__)
 
   if initial_args.tool_binary:
     tool_basename = os.path.basename(initial_args.tool_binary)
     if not re.match(r'^%s(-\d+)?(\.exe)?$' % (initial_args.tool), tool_basename):
       common.error('Unexpected tool name: ' + tool_basename)
       sys.exit(1)