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.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@223147 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/MC/MCSubtargetInfo.h

@@ -136,6 +136,15 @@ public:
 
   /// Initialize an InstrItineraryData instance.
   void initInstrItins(InstrItineraryData &InstrItins) const;
+
+  /// Check whether the CPU string is valid.
+  bool CPUStringIsValid(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

lib/Target/ARM/AsmParser/ARMAsmParser.cpp

@@ -9083,6 +9083,17 @@ bool ARMAsmParser::parseDirectiveEabiAttr(SMLoc L) {
 bool ARMAsmParser::parseDirectiveCPU(SMLoc L) {
   StringRef CPU = getParser().parseStringToEndOfStatement().trim();
   getTargetStreamer().emitTextAttribute(ARMBuildAttrs::CPU_name, CPU);
+
+  if (!STI.CPUStringIsValid(CPU)) {
+    Error(L, "Unknown CPU name");
+    return false;
+  }
+
+  STI.InitMCProcessorInfo(CPU, "");
+  STI.InitCPUSchedModel(CPU);
+  unsigned FB = ComputeAvailableFeatures(STI.getFeatureBits());
+  setAvailableFeatures(FB);
+
   return false;
 }
 

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