ARM: Error out on apple darwin platforms if float-abi is "hard"

[ahatanak]

Summary

Error out if user provides -mfloat-abi=hard or -mhard-float on the command line since hard float abi isn't supported on apple platforms (except for non-darwin platforms).

[vsk]

LGTM.

cfe/trunk/lib/Driver/Tools.cpp

else if (A->getOption().matches(options::OPT_mhard_float))
       FloatABI = "hard";
     else {
       FloatABI = A->getValue();
       if (FloatABI != "soft" && FloatABI != "softfp" && FloatABI != "hard") {
         D.Diag(diag::err_drv_invalid_mfloat_abi) << A->getAsString(Args);
         FloatABI = "soft";
       }
     }
+
+    if (Triple.isOSDarwin() && FloatABI == "hard")
+      D.Diag(diag::err_drv_unsupported_opt_for_target) << A->getAsString(Args)
+                                                       << Triple.getArchName();
   }
 
   // If unspecified, choose the default based on the platform.
   if (FloatABI.empty()) {
     switch (Triple.getOS()) {
     case llvm::Triple::Darwin:
     case llvm::Triple::MacOSX:
     case llvm::Triple::IOS: {

cfe/trunk/test/Driver/arm-float-abi.c

+// RUN: not %clang %s -target armv7-apple-ios -mfloat-abi=hard 2>&1 | FileCheck -check-prefix=ARMV7-HARD %s
+// RUN: %clang %s -target armv7-apple-ios -mfloat-abi=softfp -### 2>&1 | FileCheck -check-prefix=ARMV7-SOFTFP %s
+
+// ARMV7-HARD: unsupported option '-mfloat-abi=hard' for target 'thumbv7'
+// ARMV7-SOFTFP-NOT: unsupported option