Pull in r223147, r223255 and r223390 from upstream llvm trunk (by Roman
Divacky):

  Introduce CPUStringIsValid() into MCSubtargetInfo and use it for ARM
  .cpu parsing.

  Previously .cpu directive in ARM assembler didnt switch to the new
  CPU and therefore acted as a nop. This implemented real action for
  .cpu and eg. allows to assembler FreeBSD kernel with -integrated-as.

  Change the name to be in style.

  Add a FIXME as requested by Renato Golin.

Introduced here: http://svnweb.freebsd.org/changeset/base/275654

Index: include/llvm/MC/MCSubtargetInfo.h
===================================================================
--- include/llvm/MC/MCSubtargetInfo.h
+++ include/llvm/MC/MCSubtargetInfo.h
@@ -132,6 +132,15 @@ class MCSubtargetInfo {
 
   /// Initialize an InstrItineraryData instance.
   void initInstrItins(InstrItineraryData &InstrItins) const;
+
+  /// Check whether the CPU string is valid.
+  bool isCPUStringValid(StringRef CPU) {
+    auto Found = std::find_if(ProcDesc.begin(), ProcDesc.end(),
+                              [=](const SubtargetFeatureKV &KV) {
+                                return CPU == KV.Key; 
+                              });
+    return Found != ProcDesc.end();
+  }
 };
 
 } // End llvm namespace
Index: lib/Target/ARM/AsmParser/ARMAsmParser.cpp
===================================================================
--- lib/Target/ARM/AsmParser/ARMAsmParser.cpp
+++ lib/Target/ARM/AsmParser/ARMAsmParser.cpp
@@ -8618,6 +8618,20 @@ bool ARMAsmParser::parseDirectiveEabiAttr(SMLoc L)
 bool ARMAsmParser::parseDirectiveCPU(SMLoc L) {
   StringRef CPU = getParser().parseStringToEndOfStatement().trim();
   getTargetStreamer().emitTextAttribute(ARMBuildAttrs::CPU_name, CPU);
+
+  if (!STI.isCPUStringValid(CPU)) {
+    Error(L, "Unknown CPU name");
+    return false;
+  }
+
+  // FIXME: This switches the CPU features globally, therefore it might
+  // happen that code you would not expect to assemble will. For details
+  // see: http://llvm.org/bugs/show_bug.cgi?id=20757
+  STI.InitMCProcessorInfo(CPU, "");
+  STI.InitCPUSchedModel(CPU);
+  unsigned FB = ComputeAvailableFeatures(STI.getFeatureBits());
+  setAvailableFeatures(FB);
+
   return false;
 }
 
Index: test/MC/ARM/cpu-test.s
===================================================================
--- test/MC/ARM/cpu-test.s
+++ test/MC/ARM/cpu-test.s
@@ -0,0 +1,13 @@
+// RUN: not llvm-mc -o - -triple arm-gnueabi-freebsd11.0 < %s > %t 2> %t2
+// RUN: FileCheck %s < %t
+// RUN: FileCheck %s --check-prefix=CHECK-ERROR < %t2
+
+// CHECK: .cpu cortex-a8
+.cpu cortex-a8
+// CHECK: dsb     sy
+dsb
+.cpu arm9       
+// CHECK-ERROR: error: instruction requires: data-barriers
+dsb
+// CHECK-ERROR: error: Unknown CPU name
+.cpu foobar