[driver] Create a new -mfpmath= option, which is used to control whether clang

uses Neon instructions for single-precision FP.

-mfpmath=neon is analogous to passing llc -mattr=+neonfp.
-mfpmath=[vfp|vfp2|vfp3|vfp4] is analogous to passing llc -mattr=-neonfp.

rdar://11108618

llvm-svn: 154046

clang/include/clang/Driver/Options.td

@@ -606,6 +606,7 @@ def mcpu_EQ : Joined<"-mcpu=">, Group<m_Group>;
 def mdynamic_no_pic : Joined<"-mdynamic-no-pic">, Group<m_Group>, Flags<[NoArgumentUnused]>;
 def mfix_and_continue : Flag<"-mfix-and-continue">, Group<clang_ignored_m_Group>;
 def mfloat_abi_EQ : Joined<"-mfloat-abi=">, Group<m_Group>;
+def mfpmath_EQ : Joined<"-mfpmath=">, Group<m_Group>;
 def mfpu_EQ : Joined<"-mfpu=">, Group<m_Group>;
 def mglobal_merge : Flag<"-mglobal-merge">, Group<m_Group>;
 def mhard_float : Flag<"-mhard-float">, Group<m_Group>;

clang/lib/Basic/Targets.cpp

@@ -2730,7 +2730,8 @@ public:
                                  StringRef Name,
                                  bool Enabled) const {
     if (Name == "soft-float" || Name == "soft-float-abi" ||
-        Name == "vfp2" || Name == "vfp3" || Name == "neon" || Name == "d16") {
+        Name == "vfp2" || Name == "vfp3" || Name == "neon" || Name == "d16" ||
+        Name == "neonfp") {
       Features[Name] = Enabled;
     } else
       return false;

clang/lib/Driver/Tools.cpp

@@ -504,6 +504,23 @@ static bool isSignedCharDefault(const llvm::Triple &Triple) {
   }
 }
 
+// Handle -mfpmath=.
+static void addFPMathArgs(const Driver &D, const Arg *A, const ArgList &Args,
+                          ArgStringList &CmdArgs) {
+  StringRef FPMath = A->getValue(Args);
+  
+  // Set the target features based on the FPMath.
+  if (FPMath == "neon") {
+    CmdArgs.push_back("-target-feature");
+    CmdArgs.push_back("+neonfp");
+  } else if (FPMath == "vfp" || FPMath == "vfp2" || FPMath == "vfp3" ||
+             FPMath == "vfp4") {
+    CmdArgs.push_back("-target-feature");
+    CmdArgs.push_back("-neonfp");
+  } else
+    D.Diag(diag::err_drv_clang_unsupported) << A->getAsString(Args);
+}
+
 void Clang::AddARMTargetArgs(const ArgList &Args,
                              ArgStringList &CmdArgs,
                              bool KernelOrKext) const {
@@ -686,6 +703,10 @@ void Clang::AddARMTargetArgs(const ArgList &Args,
       D.Diag(diag::err_drv_clang_unsupported) << A->getAsString(Args);
   }
 
+  // Honor -mfpmath=.
+  if (const Arg *A = Args.getLastArg(options::OPT_mfpmath_EQ))
+    addFPMathArgs(D, A, Args, CmdArgs);
+
   // Setting -msoft-float effectively disables NEON because of the GCC
   // implementation, although the same isn't true of VFP or VFP3.
   if (FloatABI == "soft") {
@@ -2688,6 +2709,10 @@ void ClangAs::AddARMTargetArgs(const ArgList &Args,
     } else
       D.Diag(diag::err_drv_clang_unsupported) << A->getAsString(Args);
   }
+
+  // Honor -mfpmath=.
+  if (const Arg *A = Args.getLastArg(options::OPT_mfpmath_EQ))
+    addFPMathArgs(D, A, Args, CmdArgs);
 }
 
 void ClangAs::ConstructJob(Compilation &C, const JobAction &JA,

clang/test/Driver/arm-mfpmath.c

@@ -0,0 +1,25 @@
+// Test different values of -mfpmath.
+
+// RUN: %clang -target arm-apple-darwin10 -mfpmath=vfp %s -### -c -o %t.o 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-VFP %s
+// CHECK-VFP: "-target-feature" "-neonfp"
+
+// RUN: %clang -target arm-apple-darwin10 -mfpmath=vfp2 %s -### -c -o %t.o 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-VFP2 %s
+// CHECK-VFP2: "-target-feature" "-neonfp"
+
+// RUN: %clang -target arm-apple-darwin10 -mfpmath=vfp3 %s -### -c -o %t.o 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-VFP3 %s
+// CHECK-VFP3: "-target-feature" "-neonfp"
+
+// RUN: %clang -target arm-apple-darwin10 -mfpmath=vfp4 %s -### -c -o %t.o 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-VFP4 %s
+// CHECK-VFP4: "-target-feature" "-neonfp"
+
+// RUN: %clang -target arm-apple-darwin10 -mfpmath=neon %s -### -c -o %t.o 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-NEON %s
+// CHECK-NEON: "-target-feature" "+neonfp"
+
+// RUN: %clang -target arm-apple-darwin10 -mfpmath=foo %s -### -c -o %t.o 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-ERROR %s
+// CHECK-ERROR: clang compiler does not support '-mfpmath=foo'