[mips] Add support for -mfpxx and -mno-fpxx.

[atanasyan]

LGTM

[dsanders]

After further manual testing (in particular comparing objects between GAS and
Clang) it became necessary to rewrite the patch. I think this will need
re-review before I commit.

Removed -mno-fpxx since it doesn't exist in other tools.
-mfpxx now implies -mno-odd-spreg.

[atanasyan]

Looks good

[dsanders]

Closed by commit rL213132 (authored by @dsanders).

include/clang/Driver/Options.td

def mips64 : Flag<["-"], "mips64">,
   Alias<march_EQ>, AliasArgs<["mips64"]>,
   HelpText<"Equivalent to -march=mips64">, Flags<[HelpHidden]>;
 def mips64r2 : Flag<["-"], "mips64r2">,
   Alias<march_EQ>, AliasArgs<["mips64r2"]>,
   HelpText<"Equivalent to -march=mips64r2">, Flags<[HelpHidden]>;
 def mips64r6 : Flag<["-"], "mips64r6">,
   Alias<march_EQ>, AliasArgs<["mips64r6"]>,
   HelpText<"Equivalent to -march=mips64r6">, Flags<[HelpHidden]>;
+def mfpxx : Flag<["-"], "mfpxx">, Group<m_Group>,
+  HelpText<"Avoid FPU mode dependent operations when used with the O32 ABI">,
+  Flags<[HelpHidden]>;
 def modd_spreg : Flag<["-"], "modd-spreg">, Group<m_Group>,
   HelpText<"Enable odd single-precision floating point registers">,
   Flags<[HelpHidden]>;
 def mno_odd_spreg : Flag<["-"], "mno-odd-spreg">, Group<m_Group>,
   HelpText<"Disable odd single-precision floating point registers">,
   Flags<[HelpHidden]>;
 def module_file_info : Flag<["-"], "module-file-info">, Flags<[DriverOption,CC1Option]>, Group<Action_Group>;
 def mthumb : Flag<["-"], "mthumb">, Group<m_Group>;

lib/Driver/Tools.cpp

static void getMIPSTargetFeatures(const Driver &D, const ArgList &Args,
   AddTargetFeature(Args, Features, options::OPT_mdsp, options::OPT_mno_dsp,
                    "dsp");
   AddTargetFeature(Args, Features, options::OPT_mdspr2, options::OPT_mno_dspr2,
                    "dspr2");
   AddTargetFeature(Args, Features, options::OPT_mmsa, options::OPT_mno_msa,
                    "msa");
   AddTargetFeature(Args, Features, options::OPT_mfp64, options::OPT_mfp32,
                    "fp64");
+  if (Args.getLastArg(options::OPT_mfpxx)) {
+    Features.push_back(Args.MakeArgString("+fpxx"));
+    Features.push_back(Args.MakeArgString("+nooddspreg"));
+  }
   AddTargetFeature(Args, Features, options::OPT_mno_odd_spreg,
                    options::OPT_modd_spreg, "nooddspreg");
 }
 
 void Clang::AddMIPSTargetArgs(const ArgList &Args,
                               ArgStringList &CmdArgs) const {
   const Driver &D = getToolChain().getDriver();
   StringRef CPUName;

test/Driver/mips-features.c

 // RUN:   | FileCheck --check-prefix=CHECK-MODDSPREG %s
 // CHECK-MODDSPREG: "-target-feature" "-nooddspreg"
 //
 // -mno-odd-spreg
 // RUN: %clang -target mips-linux-gnu -### -c %s -modd-spreg -mno-odd-spreg 2>&1 \
 // RUN:   | FileCheck --check-prefix=CHECK-NOMODDSPREG %s
 // CHECK-NOMODDSPREG: "-target-feature" "+nooddspreg"
 //
+// -mfpxx
+// RUN: %clang -target mips-linux-gnu -### -c %s -mfpxx 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-MFPXX %s
+// CHECK-MFPXX: "-target-feature" "+fpxx"
+// CHECK-MFPXX: "-target-feature" "+nooddspreg"
+//
+// -mfpxx -modd-spreg
+// RUN: %clang -target mips-linux-gnu -### -c %s -mfpxx -modd-spreg 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-MFPXX-ODDSPREG %s
+// CHECK-MFPXX-ODDSPREG: "-target-feature" "+fpxx"
+// CHECK-MFPXX-ODDSPREG: "-target-feature" "-nooddspreg"
+//
 // -mfp64
 // RUN: %clang -target mips-linux-gnu -### -c %s \
 // RUN:     -mfp32 -mfp64 2>&1 \
 // RUN:   | FileCheck --check-prefix=CHECK-MFP64 %s
 // CHECK-MFP64: "-target-feature" "+fp64"
 //
 // -mfp32
 // RUN: %clang -target mips-linux-gnu -### -c %s \