Index: lib/Target/ARM/AsmParser/ARMAsmParser.cpp
===================================================================
--- lib/Target/ARM/AsmParser/ARMAsmParser.cpp
+++ lib/Target/ARM/AsmParser/ARMAsmParser.cpp
@@ -4023,7 +4023,7 @@
   unsigned IFlags = 0;
   if (IFlagsStr != "none") {
         for (int i = 0, e = IFlagsStr.size(); i != e; ++i) {
-      unsigned Flag = StringSwitch<unsigned>(IFlagsStr.substr(i, 1))
+      unsigned Flag = StringSwitch<unsigned>(IFlagsStr.substr(i, 1).lower())
         .Case("a", ARM_PROC::A)
         .Case("i", ARM_PROC::I)
         .Case("f", ARM_PROC::F)
Index: test/MC/ARM/basic-arm-instructions.s
===================================================================
--- test/MC/ARM/basic-arm-instructions.s
+++ test/MC/ARM/basic-arm-instructions.s
@@ -791,10 +791,12 @@
 @ CPS
 @------------------------------------------------------------------------------
         cpsie  aif
+        cpsie  AIF
         cps  #15
         cpsid  if, #10
 
 @ CHECK: cpsie  aif @ encoding: [0xc0,0x01,0x08,0xf1]
+@ CHECK: cpsie  aif @ encoding: [0xc0,0x01,0x08,0xf1]
 @ CHECK: cps  #15 @ encoding: [0x0f,0x00,0x02,0xf1]
 @ CHECK: cpsid  if, #10 @ encoding: [0xca,0x00,0x0e,0xf1]