XCore target: add -march flag handling

[robertlytton]

Summary

The -march setting needs to be passed to the assembler and linker if it is specified.
A default of "-march=xs1b" is used if it is not specified - or would you prefer not to emit it?

[robertlytton]

Not yet... maybe another mechanism...

lib/Driver/Tools.cpp

 /// XCore Tools
 // We pass assemble and link construction to the xcc tool.
 
+static const char *getXCoreMarch(const ArgList &Args) {
+  if (const Arg *A = Args.getLastArg(options::OPT_march_EQ))
+    return A->getValue();
+  return "xs1b";
+}
+
 void XCore::Assemble::ConstructJob(Compilation &C, const JobAction &JA,
                                        const InputInfo &Output,
                                        const InputInfoList &Inputs,

     if (!A->getOption().matches(options::OPT_g0))
       CmdArgs.push_back("-g");
 
+  StringRef March = getXCoreMarch(Args);
+  CmdArgs.push_back(Args.MakeArgString("-march=" + March));
+
   if (Args.hasFlag(options::OPT_fverbose_asm, options::OPT_fno_verbose_asm,
                    false))
     CmdArgs.push_back("-fverbose-asm");

   if (Args.hasArg(options::OPT_v))
     CmdArgs.push_back("-v");
 
+  StringRef March = getXCoreMarch(Args);
+  CmdArgs.push_back(Args.MakeArgString("-march=" + March));
+
   ExceptionSettings EH = exceptionSettings(Args, getToolChain().getTriple());
   if (EH.ShouldUseExceptionTables)
     CmdArgs.push_back("-fexceptions");

test/Driver/xcore-opts.c

 // RUN: %clang -target xcore -x c++ %s -g -Wl,L1Arg,L2Arg -Wa,A1Arg,A2Arg -fverbose-asm -v -### -o %t.o 2>&1 | FileCheck %s
 // RUN: %clang -target xcore -x c++ %s -fexceptions -### -o %t.o 2>&1 | FileCheck -check-prefix CHECK-EXCEP %s
 // RUN: %clang -target xcore %s -g0 -### -o %t.o 2>&1 | FileCheck -check-prefix CHECK-G0 %s
+// RUN: %clang -target xcore %s -march=xs0a -### -o %t.o 2>&1 | FileCheck -check-prefix CHECK-MARCH %s
 
 // CHECK: "-nostdsysteminc"
 // CHECK: "-momit-leaf-frame-pointer"

 // CHECK: "-fno-common"
 // CHECK: xcc" "-o"
 // CHECK-EXCEP-NOT: "-fexceptions"
-// CHECK: "-c" "-v" "-g" "-fverbose-asm" "A1Arg" "A2Arg"
+// CHECK: "-c" "-v" "-g" "-march=xs1b" "-fverbose-asm" "A1Arg" "A2Arg"
 // CHECK: xcc" "-o"
 // CHECK-EXCEP-NOT: "-fexceptions"
-// CHECK: "-v"
+// CHECK: "-v" "-march=xs1b"
 // CHECK: "L1Arg" "L2Arg"
 
 // CHECK-EXCEP: "-fno-use-cxa-atexit"

 // CHECK-G0-NOT: "-g"
 // CHECK-G0: xcc"
 
+// CHECK-MARCH: xcc"
+// CHECK-MARCH: "-march=xs0a"
+// CHECK-MARCH: xcc"
+// CHECK-MARCH: "-march=xs0a"