Index: lib/Driver/Tools.cpp
===================================================================
--- lib/Driver/Tools.cpp
+++ lib/Driver/Tools.cpp
@@ -5752,7 +5752,7 @@
   // FIXME: Warn on inconsistent use of -mcpu and -march.
   // If we have -mcpu=, use that.
   if (Arg *A = Args.getLastArg(options::OPT_mcpu_EQ)) {
-    StringRef MCPU = A->getValue();
+    StringRef MCPU = StringRef(A->getValue()).lower();
     // Handle -mcpu=native.
     if (MCPU == "native")
       return llvm::sys::getHostCPUName();
@@ -7601,7 +7601,7 @@
     // march from being picked in the absence of a cpu flag.
     Arg *A;
     if ((A = Args.getLastArg(options::OPT_mcpu_EQ)) &&
-      StringRef(A->getValue()) == "krait")
+      StringRef(A->getValue()).lower() == "krait")
         CmdArgs.push_back("-march=armv7-a");
     else
       Args.AddLastArg(CmdArgs, options::OPT_mcpu_EQ);
Index: test/Driver/arm-cortex-cpus.c
===================================================================
--- test/Driver/arm-cortex-cpus.c
+++ test/Driver/arm-cortex-cpus.c
@@ -392,3 +392,13 @@
 // RUN: %clang -target arm -mcpu=cortex-a57 -mbig-endian -mthumb -### -c %s 2>&1 | FileCheck -check-prefix=CHECK-BE-CPUV8A-THUMB %s
 // RUN: %clang -target arm -mcpu=cortex-a72 -mbig-endian -mthumb -### -c %s 2>&1 | FileCheck -check-prefix=CHECK-BE-CPUV8A-THUMB %s
 // CHECK-BE-CPUV8A-THUMB: "-cc1"{{.*}} "-triple" "thumbebv8-{{.*}}
+
+// ================== Check whether -mcpu accepts mixed-case values.
+// RUN: %clang -target arm-linux-gnueabi -mcpu=Cortex-a5 -### -c %s 2>&1 | FileCheck -check-prefix=CHECK-CASE-INSENSITIVE-CPUV7A %s
+// RUN: %clang -target arm-linux-gnueabi -mcpu=cortex-A7 -### -c %s 2>&1 | FileCheck -check-prefix=CHECK-CASE-INSENSITIVE-CPUV7A %s
+// RUN: %clang -target arm-linux-gnueabi -mcpu=CORTEX-a8 -### -c %s 2>&1 | FileCheck -check-prefix=CHECK-CASE-INSENSITIVE-CPUV7A %s
+// RUN: %clang -target arm-linux-gnueabi -mcpu=Cortex-A9 -### -c %s 2>&1 | FileCheck -check-prefix=CHECK-CASE-INSENSITIVE-CPUV7A %s
+// RUN: %clang -target arm-linux-gnueabi -mcpu=corteX-A12 -### -c %s 2>&1 | FileCheck -check-prefix=CHECK-CASE-INSENSITIVE-CPUV7A %s
+// RUN: %clang -target arm-linux-gnueabi -mcpu=CorteX-a15 -### -c %s 2>&1 | FileCheck -check-prefix=CHECK-CASE-INSENSITIVE-CPUV7A %s
+// RUN: %clang -target arm-linux-gnueabi -mcpu=CorteX-A17 -### -c %s 2>&1 | FileCheck -check-prefix=CHECK-CASE-INSENSITIVE-CPUV7A %s
+// CHECK-CASE-INSENSITIVE-CPUV7A: "-cc1"{{.*}} "-triple" "armv7-{{.*}}