Merge pull request halide#282 from white-pony/master

Added minval_f32/maxval_f32 functions for the OpenCL target

Author: abadams

src/CodeGen_OpenCL_Dev.cpp

@@ -353,7 +353,9 @@ void CodeGen_OpenCL_Dev::init_module() {
     src_stream << "#pragma OPENCL FP_CONTRACT ON\n";
 
     // Write out the Halide math functions.
-    src_stream << "float nan_f32() { return NAN; }\n"
+    src_stream << "float maxval_f32() {return FLT_MAX;}\n"
+               << "float minval_f32() {return -FLT_MAX;}\n"
+               << "float nan_f32() { return NAN; }\n"
                << "float neg_inf_f32() { return -INFINITY; }\n"
                << "float inf_f32() { return INFINITY; }\n"
                << "float float_from_bits(unsigned int x) {return as_float(x);}\n"