Add scalar lowering for sqrt intrinsic.

crosstest/test_fcmp_main.cpp

 /* crosstest.py --test=test_fcmp.pnacl.ll --driver=test_fcmp_main.cpp \
    --prefix=Subzero_ --output=test_fcmp */
 
 #include <cassert>
 #include <cfloat>
 #include <cmath>
 #include <iostream>
 
 #include "test_fcmp.def"
 
 #define X(cmp)                                                                 \
   extern "C" bool fcmp##cmp##Float(float a, float b);                          \
   extern "C" bool fcmp##cmp##Double(double a, double b);                       \
   extern "C" bool Subzero_fcmp##cmp##Float(float a, float b);                  \
   extern "C" bool Subzero_fcmp##cmp##Double(double a, double b);
 FCMP_TABLE;
 #undef X
 
 int main(int argc, char **argv) {
   static const double NegInf = -1.0 / 0.0;
   static const double Zero = 0.0;
   static const double Ten = 10.0;
   static const double PosInf = 1.0 / 0.0;
   static const double Nan = 0.0 / 0.0;
+  static const double NegNan = -0.0 / 0.0;
   assert(std::fpclassify(NegInf) == FP_INFINITE);
   assert(std::fpclassify(PosInf) == FP_INFINITE);
   assert(std::fpclassify(Nan) == FP_NAN);
+  assert(std::fpclassify(NegNan) == FP_NAN);
   assert(NegInf < Zero);
   assert(NegInf < PosInf);
   assert(Zero < PosInf);
 
-  volatile double Values[] = { NegInf,  Zero,    DBL_MIN, FLT_MIN, Ten,
-                               FLT_MAX, DBL_MAX, PosInf,  Nan, };
+  volatile double Values[] = { NegInf, -Zero,   Zero,    DBL_MIN, FLT_MIN,
+                               Ten,    FLT_MAX, DBL_MAX, PosInf,  Nan,
+                               NegNan };
   const static size_t NumValues = sizeof(Values) / sizeof(*Values);
 
   typedef bool (*FuncTypeFloat)(float, float);
   typedef bool (*FuncTypeDouble)(double, double);
   static struct {
     const char *Name;
     FuncTypeFloat FuncFloatSz;
     FuncTypeFloat FuncFloatLlc;
     FuncTypeDouble FuncDoubleSz;
     FuncTypeDouble FuncDoubleLlc;
@@ skipping 45 matching lines @@
                     << " llc=" << ResultLlc << std::endl;
         }
       }
     }
   }
 
   std::cout << "TotalTests=" << TotalTests << " Passes=" << Passes
             << " Failures=" << Failures << "\n";
   return Failures;
 }