diff --git a/llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/UTC_ARGS.ll b/llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/UTC_ARGS.ll
new file mode 100644
--- /dev/null
+++ b/llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/UTC_ARGS.ll
@@ -0,0 +1,59 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --function-signature      --check-attributes
+; Example input for update_test_checks (taken from test/Transforms/InstSimplify/add.ll)
+; RUN: opt < %s -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
+}
+
+define i32 @negated_operand(i32 %x) {
+; CHECK-LABEL: @negated_operand(
+; 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-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-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-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-NEXT:    ret i32 [[TMP1]]
+;
+  %1 = sub i32 42, %X
+  ret i32 %1
+}
diff --git a/llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/UTC_ARGS.ll.expected b/llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/UTC_ARGS.ll.expected
new file mode 100644
--- /dev/null
+++ b/llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/UTC_ARGS.ll.expected
@@ -0,0 +1,65 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --function-signature --check-attributes
+; Example input for update_test_checks (taken from test/Transforms/InstSimplify/add.ll)
+; RUN: opt < %s -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
+}
diff --git a/llvm/test/tools/UpdateTestChecks/update_test_checks/UTC_ARGS.test b/llvm/test/tools/UpdateTestChecks/update_test_checks/UTC_ARGS.test
new file mode 100644
--- /dev/null
+++ b/llvm/test/tools/UpdateTestChecks/update_test_checks/UTC_ARGS.test
@@ -0,0 +1,7 @@
+# REQUIRES: x86-registered-target
+## UTC_ARGS test checking that update_test_checks.py works correctly
+# RUN: cp -f %S/Inputs/UTC_ARGS.ll %t.ll && %update_test_checks %t.ll
+# RUN: diff -u %t.ll %S/Inputs/UTC_ARGS.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/UTC_ARGS.ll.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
@@ -588,8 +588,9 @@
 def check_for_command(line, parser, args, argv, argparse_callback):
     cmd_m = UTC_ARGS_CMD.match(line)
     if cmd_m:
-        cmd = cmd_m.group('cmd').strip().split(' ')
-        argv = argv + cmd
+        for option in cmd_m.group('cmd').strip().split(' '):
+            if option:
+                argv.append(option)
         args = parser.parse_args(filter(lambda arg: arg not in args.tests, argv))
         if argparse_callback is not None:
           argparse_callback(args)