Index: lib/Driver/Tools.cpp
===================================================================
--- lib/Driver/Tools.cpp
+++ lib/Driver/Tools.cpp
@@ -1320,47 +1320,31 @@
   return "";
 }
 
+// Only the hard-float ABI on Sparc is standardized, and it is the
+// default. GCC also supports a nonstandard soft-float ABI mode, and
+// perhaps LLVM should implement that, too. However, since llvm
+// currently does not support Sparc soft-float, at all, display an
+// error if it's requested.
+
 static void getSparcTargetFeatures(const ArgList &Args,
                                    std::vector<const char *> &Features) {
-  bool SoftFloatABI = true;
-  if (Arg *A =
-          Args.getLastArg(options::OPT_msoft_float, options::OPT_mhard_float)) {
-    if (A->getOption().matches(options::OPT_mhard_float))
-      SoftFloatABI = false;
-  }
-  if (SoftFloatABI)
-    Features.push_back("+soft-float");
 }
 
 void Clang::AddSparcTargetArgs(const ArgList &Args,
                              ArgStringList &CmdArgs) const {
   const Driver &D = getToolChain().getDriver();
+  std::string Triple = getToolChain().ComputeEffectiveClangTriple(Args);
 
-  // Select the float ABI as determined by -msoft-float and -mhard-float.
-  StringRef FloatABI;
-  if (Arg *A = Args.getLastArg(options::OPT_msoft_float,
-                               options::OPT_mhard_float)) {
+  bool SoftFloatABI = false;
+  if (Arg *A =
+          Args.getLastArg(options::OPT_msoft_float, options::OPT_mhard_float)) {
     if (A->getOption().matches(options::OPT_msoft_float))
-      FloatABI = "soft";
-    else if (A->getOption().matches(options::OPT_mhard_float))
-      FloatABI = "hard";
+      SoftFloatABI = true;
   }
 
-  // If unspecified, choose the default based on the platform.
-  if (FloatABI.empty()) {
-    // Assume "soft", but warn the user we are guessing.
-    FloatABI = "soft";
-    D.Diag(diag::warn_drv_assuming_mfloat_abi_is) << "soft";
-  }
-
-  if (FloatABI == "soft") {
-    // Floating point operations and argument passing are soft.
-    //
-    // FIXME: This changes CPP defines, we need -target-soft-float.
-    CmdArgs.push_back("-msoft-float");
-  } else {
-    assert(FloatABI == "hard" && "Invalid float abi!");
-    CmdArgs.push_back("-mhard-float");
+  if (SoftFloatABI) {
+    D.Diag(diag::err_drv_unsupported_opt_for_target)
+        << "-msoft-float" << Triple;
   }
 }
 
Index: test/Driver/sparc-float.c
===================================================================
--- test/Driver/sparc-float.c
+++ test/Driver/sparc-float.c
@@ -5,38 +5,36 @@
 // RUN: %clang -c %s -### -o %t.o 2>&1 \
 // RUN:     -target sparc-linux-gnu \
 // RUN:   | FileCheck --check-prefix=CHECK-DEF %s
-// CHECK-DEF: "-target-feature" "+soft-float"
-// CHECK-DEF: "-msoft-float"
+// CHECK-DEF-NOT: "-target-feature" "+soft-float"
+// CHECK-DEF-NOT: "-msoft-float"
 //
 // -mhard-float
 // RUN: %clang -c %s -### -o %t.o 2>&1 \
 // RUN:     -target sparc-linux-gnu -mhard-float \
 // RUN:   | FileCheck --check-prefix=CHECK-HARD %s
-// CHECK-HARD: "-mhard-float"
+// CHECK-HARD-NOT: "-msoft-float"
 //
 // -msoft-float
 // RUN: %clang -c %s -### -o %t.o 2>&1 \
 // RUN:     -target sparc-linux-gnu -msoft-float \
 // RUN:   | FileCheck --check-prefix=CHECK-SOFT %s
-// CHECK-SOFT: "-target-feature" "+soft-float"
-// CHECK-SOFT: "-msoft-float"
+// CHECK-SOFT: error: unsupported option '-msoft-float'
 //
 // Default sparc64
 // RUN: %clang -c %s -### -o %t.o 2>&1 \
 // RUN:     -target sparc64-linux-gnu \
 // RUN:   | FileCheck --check-prefix=CHECK-DEF-SPARC64 %s
-// CHECK-DEF-SPARC64: "-target-feature" "+soft-float"
-// CHECK-DEF-SPARC64: "-msoft-float"
+// CHECK-DEF-SPARC64-NOT: "-target-feature" "+soft-float"
+// CHECK-DEF-SPARC64-NOT: "-msoft-float"
 //
 // -mhard-float
 // RUN: %clang -c %s -### -o %t.o 2>&1 \
 // RUN:     -target sparc64-linux-gnu -mhard-float \
 // RUN:   | FileCheck --check-prefix=CHECK-HARD-SPARC64 %s
-// CHECK-HARD-SPARC64: "-mhard-float"
+// CHECK-HARD-SPARC64-NOT: "-msoft-float"
 //
 // -msoft-float
 // RUN: %clang -c %s -### -o %t.o 2>&1 \
 // RUN:     -target sparc64-linux-gnu -msoft-float \
 // RUN:   | FileCheck --check-prefix=CHECK-SOFT-SPARC64 %s
-// CHECK-SOFT-SPARC64: "-target-feature" "+soft-float"
-// CHECK-SOFT-SPARC64: "-msoft-float"
+// CHECK-SOFT-SPARC64: error: unsupported option '-msoft-float'