diff --git a/llvm/test/tools/UpdateTestChecks/lit.local.cfg b/llvm/test/tools/UpdateTestChecks/lit.local.cfg
new file mode 100644
--- /dev/null
+++ b/llvm/test/tools/UpdateTestChecks/lit.local.cfg
@@ -0,0 +1,61 @@
+import os
+
+import lit.formats
+import lit.util
+
+# python 2.7 backwards compatibility
+try:
+    from shlex import quote as shell_quote
+except ImportError:
+    from pipes import quote as shell_quote
+
+
+def add_update_script_substition(name, python_exe=config.python_executable,
+                                 extra_args=''):
+    script_path = os.path.join(config.llvm_src_root, 'utils', name + '.py')
+    assert os.path.isfile(script_path)
+    config.substitutions.append(
+        ('%' + name, "'%s' %s %s" % (python_exe, script_path, extra_args)))
+
+
+config.test_format = lit.formats.ShTest(execute_external=False)
+config.suffixes = ['.test']
+
+llc_path = os.path.join(config.llvm_tools_dir, 'llc')
+if os.path.isfile(llc_path):
+    config.available_features.add('llc-binary')
+    llc_arg = '--llc-binary ' + shell_quote(llc_path)
+    add_update_script_substition('update_llc_test_checks', extra_args=llc_arg)
+    add_update_script_substition('update_mir_test_checks', extra_args=llc_arg)
+
+opt_path = os.path.join(config.llvm_tools_dir, 'opt')
+if os.path.isfile(opt_path):
+    config.available_features.add('opt-binary')
+    opt_arg = '--opt-binary ' + shell_quote(opt_path)
+    add_update_script_substition('update_test_checks', extra_args=opt_arg)
+    add_update_script_substition('update_analyze_test_checks',
+                                 extra_args=opt_arg)
+
+llvm_mca_path = os.path.join(config.llvm_tools_dir, 'llvm-mca')
+if os.path.isfile(llvm_mca_path):
+    config.available_features.add('llvm-mca-binary')
+    mca_arg = '--llvm-mca-binary ' + shell_quote(llvm_mca_path)
+    add_update_script_substition('update_test_checks', extra_args=mca_arg)
+
+# update_cc_test_checks requires python3
+py3_exe = lit.util.which('python3')
+if py3_exe:
+    config.substitutions.append(('%python3', shell_quote(py3_exe)))
+    config.available_features.add('python3')
+
+clang_path = os.path.join(config.llvm_tools_dir, 'clang')
+if os.path.isfile(clang_path):
+    config.available_features.add('clang-binary')
+    if py3_exe:
+        # XXX: or use --llvm-bin?
+        extra_args = '--clang ' + shell_quote(clang_path)
+        if os.path.isfile(opt_path):
+            extra_args += ' --opt ' + shell_quote(opt_path)
+        add_update_script_substition('update_cc_test_checks',
+                                     python_exe=py3_exe,
+                                     extra_args=extra_args)
diff --git a/llvm/test/tools/UpdateTestChecks/update_cc_test_checks/Inputs/mangled_names.c b/llvm/test/tools/UpdateTestChecks/update_cc_test_checks/Inputs/mangled_names.c
new file mode 100644
--- /dev/null
+++ b/llvm/test/tools/UpdateTestChecks/update_cc_test_checks/Inputs/mangled_names.c
@@ -0,0 +1,11 @@
+// Example input for update_cc_test_checks
+// RUN: %clang_cc1 -triple=x86_64-unknown-linux-gnu -emit-llvm -o - %s | FileCheck %s
+
+long test(long a, int b) {
+  return a + b;
+}
+
+// A function with a mangled name
+__attribute__((overloadable)) long test(long a, int b, int c) {
+  return a + b + c;
+}
diff --git a/llvm/test/tools/UpdateTestChecks/update_cc_test_checks/Inputs/mangled_names.c.expected b/llvm/test/tools/UpdateTestChecks/update_cc_test_checks/Inputs/mangled_names.c.expected
new file mode 100644
--- /dev/null
+++ b/llvm/test/tools/UpdateTestChecks/update_cc_test_checks/Inputs/mangled_names.c.expected
@@ -0,0 +1,41 @@
+// NOTE: Assertions have been autogenerated by utils/update_cc_test_checks.py
+// Example input for update_cc_test_checks
+// RUN: %clang_cc1 -triple=x86_64-unknown-linux-gnu -emit-llvm -o - %s | FileCheck %s
+
+// CHECK-LABEL: @test(
+// CHECK-NEXT:  entry:
+// CHECK-NEXT:    [[A_ADDR:%.*]] = alloca i64, align 8
+// CHECK-NEXT:    [[B_ADDR:%.*]] = alloca i32, align 4
+// CHECK-NEXT:    store i64 [[A:%.*]], i64* [[A_ADDR]], align 8
+// CHECK-NEXT:    store i32 [[B:%.*]], i32* [[B_ADDR]], align 4
+// CHECK-NEXT:    [[TMP0:%.*]] = load i64, i64* [[A_ADDR]], align 8
+// CHECK-NEXT:    [[TMP1:%.*]] = load i32, i32* [[B_ADDR]], align 4
+// CHECK-NEXT:    [[CONV:%.*]] = sext i32 [[TMP1]] to i64
+// CHECK-NEXT:    [[ADD:%.*]] = add nsw i64 [[TMP0]], [[CONV]]
+// CHECK-NEXT:    ret i64 [[ADD]]
+//
+long test(long a, int b) {
+  return a + b;
+}
+
+// A function with a mangled name
+// CHECK-LABEL: @_Z4testlii(
+// CHECK-NEXT:  entry:
+// CHECK-NEXT:    [[A_ADDR:%.*]] = alloca i64, align 8
+// CHECK-NEXT:    [[B_ADDR:%.*]] = alloca i32, align 4
+// CHECK-NEXT:    [[C_ADDR:%.*]] = alloca i32, align 4
+// CHECK-NEXT:    store i64 [[A:%.*]], i64* [[A_ADDR]], align 8
+// CHECK-NEXT:    store i32 [[B:%.*]], i32* [[B_ADDR]], align 4
+// CHECK-NEXT:    store i32 [[C:%.*]], i32* [[C_ADDR]], align 4
+// CHECK-NEXT:    [[TMP0:%.*]] = load i64, i64* [[A_ADDR]], align 8
+// CHECK-NEXT:    [[TMP1:%.*]] = load i32, i32* [[B_ADDR]], align 4
+// CHECK-NEXT:    [[CONV:%.*]] = sext i32 [[TMP1]] to i64
+// CHECK-NEXT:    [[ADD:%.*]] = add nsw i64 [[TMP0]], [[CONV]]
+// CHECK-NEXT:    [[TMP2:%.*]] = load i32, i32* [[C_ADDR]], align 4
+// CHECK-NEXT:    [[CONV1:%.*]] = sext i32 [[TMP2]] to i64
+// CHECK-NEXT:    [[ADD2:%.*]] = add nsw i64 [[ADD]], [[CONV1]]
+// CHECK-NEXT:    ret i64 [[ADD2]]
+//
+__attribute__((overloadable)) long test(long a, int b, int c) {
+  return a + b + c;
+}
diff --git a/llvm/test/tools/UpdateTestChecks/update_cc_test_checks/Inputs/mangled_names.c.funcsig.expected b/llvm/test/tools/UpdateTestChecks/update_cc_test_checks/Inputs/mangled_names.c.funcsig.expected
new file mode 100644
--- /dev/null
+++ b/llvm/test/tools/UpdateTestChecks/update_cc_test_checks/Inputs/mangled_names.c.funcsig.expected
@@ -0,0 +1,43 @@
+// NOTE: Assertions have been autogenerated by utils/update_cc_test_checks.py
+// Example input for update_cc_test_checks
+// RUN: %clang_cc1 -triple=x86_64-unknown-linux-gnu -emit-llvm -o - %s | FileCheck %s
+
+// CHECK-LABEL: define {{[^@]+}}@test
+// CHECK-SAME: (i64 [[A:%.*]], i32 [[B:%.*]]) #0
+// CHECK-NEXT:  entry:
+// CHECK-NEXT:    [[A_ADDR:%.*]] = alloca i64, align 8
+// CHECK-NEXT:    [[B_ADDR:%.*]] = alloca i32, align 4
+// CHECK-NEXT:    store i64 [[A:%.*]], i64* [[A_ADDR]], align 8
+// CHECK-NEXT:    store i32 [[B:%.*]], i32* [[B_ADDR]], align 4
+// CHECK-NEXT:    [[TMP0:%.*]] = load i64, i64* [[A_ADDR]], align 8
+// CHECK-NEXT:    [[TMP1:%.*]] = load i32, i32* [[B_ADDR]], align 4
+// CHECK-NEXT:    [[CONV:%.*]] = sext i32 [[TMP1]] to i64
+// CHECK-NEXT:    [[ADD:%.*]] = add nsw i64 [[TMP0]], [[CONV]]
+// CHECK-NEXT:    ret i64 [[ADD]]
+//
+long test(long a, int b) {
+  return a + b;
+}
+
+// A function with a mangled name
+// CHECK-LABEL: define {{[^@]+}}@_Z4testlii
+// CHECK-SAME: (i64 [[A:%.*]], i32 [[B:%.*]], i32 [[C:%.*]]) #0
+// CHECK-NEXT:  entry:
+// CHECK-NEXT:    [[A_ADDR:%.*]] = alloca i64, align 8
+// CHECK-NEXT:    [[B_ADDR:%.*]] = alloca i32, align 4
+// CHECK-NEXT:    [[C_ADDR:%.*]] = alloca i32, align 4
+// CHECK-NEXT:    store i64 [[A:%.*]], i64* [[A_ADDR]], align 8
+// CHECK-NEXT:    store i32 [[B:%.*]], i32* [[B_ADDR]], align 4
+// CHECK-NEXT:    store i32 [[C:%.*]], i32* [[C_ADDR]], align 4
+// CHECK-NEXT:    [[TMP0:%.*]] = load i64, i64* [[A_ADDR]], align 8
+// CHECK-NEXT:    [[TMP1:%.*]] = load i32, i32* [[B_ADDR]], align 4
+// CHECK-NEXT:    [[CONV:%.*]] = sext i32 [[TMP1]] to i64
+// CHECK-NEXT:    [[ADD:%.*]] = add nsw i64 [[TMP0]], [[CONV]]
+// CHECK-NEXT:    [[TMP2:%.*]] = load i32, i32* [[C_ADDR]], align 4
+// CHECK-NEXT:    [[CONV1:%.*]] = sext i32 [[TMP2]] to i64
+// CHECK-NEXT:    [[ADD2:%.*]] = add nsw i64 [[ADD]], [[CONV1]]
+// CHECK-NEXT:    ret i64 [[ADD2]]
+//
+__attribute__((overloadable)) long test(long a, int b, int c) {
+  return a + b + c;
+}
diff --git a/llvm/test/tools/UpdateTestChecks/update_cc_test_checks/lit.local.cfg b/llvm/test/tools/UpdateTestChecks/update_cc_test_checks/lit.local.cfg
new file mode 100644
--- /dev/null
+++ b/llvm/test/tools/UpdateTestChecks/update_cc_test_checks/lit.local.cfg
@@ -0,0 +1,3 @@
+# These tests require clang.
+if 'clang-binary' not in config.available_features:
+    config.unsupported = True
diff --git a/llvm/test/tools/UpdateTestChecks/update_cc_test_checks/mangled_names.test b/llvm/test/tools/UpdateTestChecks/update_cc_test_checks/mangled_names.test
new file mode 100644
--- /dev/null
+++ b/llvm/test/tools/UpdateTestChecks/update_cc_test_checks/mangled_names.test
@@ -0,0 +1,13 @@
+## Basic test checking that update_cc_test_checks.py works as expected for
+## functions with mangled names
+# RUN: cp -f %S/Inputs/mangled_names.c %t.c && %update_cc_test_checks -v %t.c
+# RUN: diff -u %t.c %S/Inputs/mangled_names.c.expected
+## Check that running the script again does not change the result:
+# RUN: %update_cc_test_checks -v %t.c
+# RUN: diff -u %t.c %S/Inputs/mangled_names.c.expected
+## Also try the --function-signature flag
+# RUN: %update_cc_test_checks %t.c --function-signature
+# RUN: diff -u %t.c %S/Inputs/mangled_names.c.funcsig.expected
+## Verify that running without the --function-signature flag removes the -SAME: lines:
+# RUN: %update_cc_test_checks %t.c
+# RUN: diff -u %t.c %S/Inputs/mangled_names.c.expected
diff --git a/llvm/test/tools/UpdateTestChecks/update_llc_test_checks/Inputs/basic.ll b/llvm/test/tools/UpdateTestChecks/update_llc_test_checks/Inputs/basic.ll
new file mode 100644
--- /dev/null
+++ b/llvm/test/tools/UpdateTestChecks/update_llc_test_checks/Inputs/basic.ll
@@ -0,0 +1,32 @@
+; Example input for update_llc_test_checks (taken from CodeGen/X86/iabs.ll)
+; RUN: llc < %s -mtriple=i686-unknown-unknown | FileCheck %s --check-prefix=X86 --check-prefix=X86-NO-CMOV
+; RUN: llc < %s -mtriple=i686-unknown-unknown -mattr=+cmov | FileCheck %s --check-prefix=X86 --check-prefix=X86-CMOV
+; RUN: llc < %s -mtriple=x86_64-unknown-unknown | FileCheck %s --check-prefix=X64
+
+define i8 @test_i8(i8 %a) nounwind {
+  %tmp1neg = sub i8 0, %a
+  %b = icmp sgt i8 %a, -1
+  %abs = select i1 %b, i8 %a, i8 %tmp1neg
+  ret i8 %abs
+}
+
+define i16 @test_i16(i16 %a) nounwind {
+  %tmp1neg = sub i16 0, %a
+  %b = icmp sgt i16 %a, -1
+  %abs = select i1 %b, i16 %a, i16 %tmp1neg
+  ret i16 %abs
+}
+
+define i32 @test_i32(i32 %a) nounwind {
+  %tmp1neg = sub i32 0, %a
+  %b = icmp sgt i32 %a, -1
+  %abs = select i1 %b, i32 %a, i32 %tmp1neg
+  ret i32 %abs
+}
+
+define i64 @test_i64(i64 %a) nounwind {
+  %tmp1neg = sub i64 0, %a
+  %b = icmp sgt i64 %a, -1
+  %abs = select i1 %b, i64 %a, i64 %tmp1neg
+  ret i64 %abs
+}
diff --git a/llvm/test/tools/UpdateTestChecks/update_llc_test_checks/Inputs/basic.ll.expected b/llvm/test/tools/UpdateTestChecks/update_llc_test_checks/Inputs/basic.ll.expected
new file mode 100644
--- /dev/null
+++ b/llvm/test/tools/UpdateTestChecks/update_llc_test_checks/Inputs/basic.ll.expected
@@ -0,0 +1,116 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; Example input for update_llc_test_checks (taken from CodeGen/X86/iabs.ll)
+; RUN: llc < %s -mtriple=i686-unknown-unknown | FileCheck %s --check-prefix=X86 --check-prefix=X86-NO-CMOV
+; RUN: llc < %s -mtriple=i686-unknown-unknown -mattr=+cmov | FileCheck %s --check-prefix=X86 --check-prefix=X86-CMOV
+; RUN: llc < %s -mtriple=x86_64-unknown-unknown | FileCheck %s --check-prefix=X64
+
+define i8 @test_i8(i8 %a) nounwind {
+; X86-LABEL: test_i8:
+; X86:       # %bb.0:
+; X86-NEXT:    movb {{[0-9]+}}(%esp), %al
+; X86-NEXT:    movl %eax, %ecx
+; X86-NEXT:    sarb $7, %cl
+; X86-NEXT:    addb %cl, %al
+; X86-NEXT:    xorb %cl, %al
+; X86-NEXT:    retl
+;
+; X64-LABEL: test_i8:
+; X64:       # %bb.0:
+; X64-NEXT:    # kill: def $edi killed $edi def $rdi
+; X64-NEXT:    movl %edi, %ecx
+; X64-NEXT:    sarb $7, %cl
+; X64-NEXT:    leal (%rdi,%rcx), %eax
+; X64-NEXT:    xorb %cl, %al
+; X64-NEXT:    # kill: def $al killed $al killed $eax
+; X64-NEXT:    retq
+  %tmp1neg = sub i8 0, %a
+  %b = icmp sgt i8 %a, -1
+  %abs = select i1 %b, i8 %a, i8 %tmp1neg
+  ret i8 %abs
+}
+
+define i16 @test_i16(i16 %a) nounwind {
+; X86-NO-CMOV-LABEL: test_i16:
+; X86-NO-CMOV:       # %bb.0:
+; X86-NO-CMOV-NEXT:    movswl {{[0-9]+}}(%esp), %eax
+; X86-NO-CMOV-NEXT:    movl %eax, %ecx
+; X86-NO-CMOV-NEXT:    sarl $15, %ecx
+; X86-NO-CMOV-NEXT:    addl %ecx, %eax
+; X86-NO-CMOV-NEXT:    xorl %ecx, %eax
+; X86-NO-CMOV-NEXT:    # kill: def $ax killed $ax killed $eax
+; X86-NO-CMOV-NEXT:    retl
+;
+; X86-CMOV-LABEL: test_i16:
+; X86-CMOV:       # %bb.0:
+; X86-CMOV-NEXT:    movzwl {{[0-9]+}}(%esp), %ecx
+; X86-CMOV-NEXT:    movl %ecx, %eax
+; X86-CMOV-NEXT:    negw %ax
+; X86-CMOV-NEXT:    cmovlw %cx, %ax
+; X86-CMOV-NEXT:    retl
+;
+; X64-LABEL: test_i16:
+; X64:       # %bb.0:
+; X64-NEXT:    movl %edi, %eax
+; X64-NEXT:    negw %ax
+; X64-NEXT:    cmovlw %di, %ax
+; X64-NEXT:    retq
+  %tmp1neg = sub i16 0, %a
+  %b = icmp sgt i16 %a, -1
+  %abs = select i1 %b, i16 %a, i16 %tmp1neg
+  ret i16 %abs
+}
+
+define i32 @test_i32(i32 %a) nounwind {
+; X86-NO-CMOV-LABEL: test_i32:
+; X86-NO-CMOV:       # %bb.0:
+; X86-NO-CMOV-NEXT:    movl {{[0-9]+}}(%esp), %eax
+; X86-NO-CMOV-NEXT:    movl %eax, %ecx
+; X86-NO-CMOV-NEXT:    sarl $31, %ecx
+; X86-NO-CMOV-NEXT:    addl %ecx, %eax
+; X86-NO-CMOV-NEXT:    xorl %ecx, %eax
+; X86-NO-CMOV-NEXT:    retl
+;
+; X86-CMOV-LABEL: test_i32:
+; X86-CMOV:       # %bb.0:
+; X86-CMOV-NEXT:    movl {{[0-9]+}}(%esp), %ecx
+; X86-CMOV-NEXT:    movl %ecx, %eax
+; X86-CMOV-NEXT:    negl %eax
+; X86-CMOV-NEXT:    cmovll %ecx, %eax
+; X86-CMOV-NEXT:    retl
+;
+; X64-LABEL: test_i32:
+; X64:       # %bb.0:
+; X64-NEXT:    movl %edi, %eax
+; X64-NEXT:    negl %eax
+; X64-NEXT:    cmovll %edi, %eax
+; X64-NEXT:    retq
+  %tmp1neg = sub i32 0, %a
+  %b = icmp sgt i32 %a, -1
+  %abs = select i1 %b, i32 %a, i32 %tmp1neg
+  ret i32 %abs
+}
+
+define i64 @test_i64(i64 %a) nounwind {
+; X86-LABEL: test_i64:
+; X86:       # %bb.0:
+; X86-NEXT:    movl {{[0-9]+}}(%esp), %edx
+; X86-NEXT:    movl %edx, %ecx
+; X86-NEXT:    sarl $31, %ecx
+; X86-NEXT:    movl {{[0-9]+}}(%esp), %eax
+; X86-NEXT:    addl %ecx, %eax
+; X86-NEXT:    adcl %ecx, %edx
+; X86-NEXT:    xorl %ecx, %edx
+; X86-NEXT:    xorl %ecx, %eax
+; X86-NEXT:    retl
+;
+; X64-LABEL: test_i64:
+; X64:       # %bb.0:
+; X64-NEXT:    movq %rdi, %rax
+; X64-NEXT:    negq %rax
+; X64-NEXT:    cmovlq %rdi, %rax
+; X64-NEXT:    retq
+  %tmp1neg = sub i64 0, %a
+  %b = icmp sgt i64 %a, -1
+  %abs = select i1 %b, i64 %a, i64 %tmp1neg
+  ret i64 %abs
+}
diff --git a/llvm/test/tools/UpdateTestChecks/update_llc_test_checks/basic.test b/llvm/test/tools/UpdateTestChecks/update_llc_test_checks/basic.test
new file mode 100644
--- /dev/null
+++ b/llvm/test/tools/UpdateTestChecks/update_llc_test_checks/basic.test
@@ -0,0 +1,15 @@
+# REQUIRES: x86-registered-target
+## Basic test checking that update_llc_test_checks.py can update a file with multiple check prefixes
+
+# RUN: cp -f %S/Inputs/basic.ll %t.ll && %update_llc_test_checks %t.ll
+# RUN: diff -u %S/Inputs/basic.ll.expected %t.ll
+## The flags --x86_scrub_rip and --extra_scrub should have any effect for this
+## test. Check the output is identical.
+# RUN: cp -f %S/Inputs/basic.ll %t.ll &&  %update_llc_test_checks --extra_scrub %t.ll
+# RUN: diff -u %S/Inputs/basic.ll.expected %t.ll
+# RUN: cp -f %S/Inputs/basic.ll %t.ll &&  %update_llc_test_checks --x86_scrub_rip %t.ll
+# RUN: diff -u %S/Inputs/basic.ll.expected %t.ll
+## Finally, run the script on an already updated file and verify that all previous
+## CHECK lines are removed.
+# RUN: %update_llc_test_checks %t.ll
+# RUN: diff -u %S/Inputs/basic.ll.expected %t.ll
diff --git a/llvm/test/tools/UpdateTestChecks/update_llc_test_checks/lit.local.cfg b/llvm/test/tools/UpdateTestChecks/update_llc_test_checks/lit.local.cfg
new file mode 100644
--- /dev/null
+++ b/llvm/test/tools/UpdateTestChecks/update_llc_test_checks/lit.local.cfg
@@ -0,0 +1,3 @@
+# These tests require llc.
+if 'llc-binary' not in config.available_features:
+    config.unsupported = True
diff --git a/llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/basic.ll b/llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/basic.ll
new file mode 100644
--- /dev/null
+++ b/llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/basic.ll
@@ -0,0 +1,49 @@
+; Example input for update_llc_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
+}
diff --git a/llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/basic.ll.expected b/llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/basic.ll.expected
new file mode 100644
--- /dev/null
+++ b/llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/basic.ll.expected
@@ -0,0 +1,50 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; Example input for update_llc_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
+}
diff --git a/llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/basic.ll.funcsig.expected b/llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/basic.ll.funcsig.expected
new file mode 100644
--- /dev/null
+++ b/llvm/test/tools/UpdateTestChecks/update_test_checks/Inputs/basic.ll.funcsig.expected
@@ -0,0 +1,55 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; Example input for update_llc_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
+}
diff --git a/llvm/test/tools/UpdateTestChecks/update_test_checks/basic.test b/llvm/test/tools/UpdateTestChecks/update_test_checks/basic.test
new file mode 100644
--- /dev/null
+++ b/llvm/test/tools/UpdateTestChecks/update_test_checks/basic.test
@@ -0,0 +1,13 @@
+# 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 removes the -SAME: lines:
+# RUN: %update_test_checks %t.ll
+# RUN: diff -u %t.ll %S/Inputs/basic.ll.expected
diff --git a/llvm/test/tools/UpdateTestChecks/update_test_checks/lit.local.cfg b/llvm/test/tools/UpdateTestChecks/update_test_checks/lit.local.cfg
new file mode 100644
--- /dev/null
+++ b/llvm/test/tools/UpdateTestChecks/update_test_checks/lit.local.cfg
@@ -0,0 +1,3 @@
+# These tests require llc.
+if 'opt-binary' not in config.available_features:
+    config.unsupported = True