fix several compile issues with Visual Studio toolchains (#2219)

Fixes several compile issues I am seeing for my version of Visual Studio
related to an ambiguous call to `fpclassify`, which is called by `isnan`
and other similar functions, specifically for the `cl_half` type:

```
19>C:\Program Files (x86)\Windows Kits\10\Include\10.0.19041.0\ucrt\corecrt_math.h(401,1): error C2668: 'fpclassify': ambiguous call to overloaded function
19>C:\Program Files (x86)\Windows Kits\10\Include\10.0.19041.0\ucrt\corecrt_math.h(298,31): message : could be 'int fpclassify(long double) throw()'
19>C:\Program Files (x86)\Windows Kits\10\Include\10.0.19041.0\ucrt\corecrt_math.h(293,31): message : or       'int fpclassify(double) throw()'
19>C:\Program Files (x86)\Windows Kits\10\Include\10.0.19041.0\ucrt\corecrt_math.h(288,31): message : or       'int fpclassify(float) throw()'
19>C:\Program Files (x86)\Windows Kits\10\Include\10.0.19041.0\ucrt\corecrt_math.h(401,1): message : while trying to match the argument list '(_Ty)'
```

Some of these issues seem like differences in compiler behavior, but at
least one appears to have identified a legitimate bug.

Specifically, this change:

* Removes the special-case checks for finite half numbers for commonfns,
since this is already handled by `UlpFn`. (test with: `test_commonfns
degrees radians`)
* Assigns to temporary variables to eliminate the ambiguous function
call for relationals. (test with: `test_relationals relational*`)
* Properly converts from half to float when checking for NaNs for
select. This is the one that seems like a legitimate bug. (test with:
`test_select select_half_ushort select_half_short`)
* Uses `std::enable_if` to disambiguate a function call for spirv_new.
(test with: `test_spirv_new decorate_saturated*`)

If it's helpful, my specific Visual Studio version is:

```
Microsoft Visual Studio Professional 2019
Version 16.11.20
VisualStudio.16.Release/16.11.20+32929.386
```

I also have the Windows Software Development Kit 10.0.19041.685
installed.

test_conformance/commonfns/test_base.h

@@ -182,27 +182,6 @@ template <typename T> inline half conv_to_half(const T &val)
     return 0;
 }
 
-template <typename T> bool isfinite_fp(const T &v)
-{
-    if (std::is_same<T, half>::value)
-    {
-        // Extract FP16 exponent and mantissa
-        uint16_t h_exp = (((half)v) >> (CL_HALF_MANT_DIG - 1)) & 0x1F;
-        uint16_t h_mant = ((half)v) & 0x3FF;
-
-        // !Inf test
-        return !(h_exp == 0x1F && h_mant == 0);
-    }
-    else
-    {
-#if !defined(_WIN32)
-        return std::isfinite(v);
-#else
-        return isfinite(v);
-#endif
-    }
-}
-
 template <typename T> float UlpFn(const T &val, const double &r)
 {
     if (std::is_same<T, half>::value)

test_conformance/commonfns/test_unary_fn.cpp

@@ -65,10 +65,6 @@ int verify_degrees(const T *const inptr, const T *const outptr, int n)
     {
         r = (180.0 / M_PI) * conv_to_dbl(inptr[i]);
 
-        if (std::is_same<T, half>::value)
-            if (!isfinite_fp(conv_to_half(r)) && !isfinite_fp(outptr[i]))
-                continue;
-
         error = UlpFn(outptr[i], r);
 
         if (fabsf(error) > max_error)
@@ -115,10 +111,6 @@ int verify_radians(const T *const inptr, const T *const outptr, int n)
     {
         r = (M_PI / 180.0) * conv_to_dbl(inptr[i]);
 
-        if (std::is_same<T, half>::value)
-            if (!isfinite_fp(conv_to_half(r)) && !isfinite_fp(outptr[i]))
-                continue;
-
         error = UlpFn(outptr[i], r);
 
         if (fabsf(error) > max_error)

test_conformance/relationals/test_comparisons_fp.cpp

@@ -368,8 +368,9 @@ int RelationalsFPTest::test_equiv_kernel(unsigned int vecSize,
                 {
                     if (gInfNanSupport == 0)
                     {
-                        if (isnan(inDataA[i * vecSize + j])
-                            || isnan(inDataB[i * vecSize + j]))
+                        float a = inDataA[i * vecSize + j];
+                        float b = inDataB[i * vecSize + j];
+                        if (isnan(a) || isnan(b))
                             fail = 0;
                         else
                             fail = 1;

test_conformance/select/util_select.cpp

@@ -18,6 +18,7 @@
 #include <stdio.h>
 #include <cinttypes>
 #include "test_select.h"
+#include "CL/cl_half.h"
 
 
 //-----------------------------------------
@@ -830,10 +831,12 @@ size_t check_half(const void *const test, const void *const correct,
 
     if (memcmp(t, c, count * sizeof(c[0])) != 0)
     {
-        for (i = 0; i < count; i++) /* Allow nans to be binary different */
-            if ((t[i] != c[i])
-                && !(isnan(((cl_half *)correct)[i])
-                     && isnan(((cl_half *)test)[i])))
+        // Allow nans to be binary different
+        for (i = 0; i < count; i++)
+        {
+            float fcorrect = cl_half_to_float(c[i]);
+            float ftest = cl_half_to_float(t[i]);
+            if ((t[i] != c[i]) && !(isnan(fcorrect) && isnan(ftest)))
             {
                 log_error("\n(check_half) Error for vector size %zu found at "
                           "0x%8.8zx (of 0x%8.8zx):  "
@@ -842,6 +845,7 @@ size_t check_half(const void *const test, const void *const correct,
                 return i + 1;
             }
         }
+    }
 
     return 0;
 }
@@ -855,9 +859,12 @@ size_t check_float(const void *const test, const void *const correct,
 
     if (memcmp(t, c, count * sizeof(c[0])) != 0)
     {
-        for (i = 0; i < count; i++) /* Allow nans to be binary different */
-            if ((t[i] != c[i])
-                && !(isnan(((float *)correct)[i]) && isnan(((float *)test)[i])))
+        // Allow nans to be binary different
+        for (i = 0; i < count; i++)
+        {
+            float fcorrect = ((float *)correct)[i];
+            float ftest = ((float *)test)[i];
+            if ((t[i] != c[i]) && !(isnan(fcorrect) && isnan(ftest)))
             {
                 log_error("\n(check_float) Error for vector size %zu found at "
                           "0x%8.8zx (of 0x%8.8zx):  "
@@ -866,6 +873,7 @@ size_t check_float(const void *const test, const void *const correct,
                 return i + 1;
             }
         }
+    }
 
     return 0;
 }

test_conformance/spirv_new/test_decorate.cpp

@@ -21,6 +21,7 @@
 #include <algorithm>
 #include <limits>
 #include <cmath>
+#include <type_traits>
 
 #include <CL/cl_half.h>
 
@@ -216,29 +217,37 @@ static inline Ti generate_saturated_rhs_input(RandomSeed &seed)
 }
 
 template <typename Ti, typename Tl, typename To>
-static inline To compute_saturated_output(Ti lhs, Ti rhs,
+static inline
+    typename std::enable_if<std::is_same<Ti, cl_half>::value, To>::type
+    compute_saturated_output(Ti lhs, Ti rhs,
                              cl_half_rounding_mode half_rounding)
 {
     constexpr auto loVal = std::numeric_limits<To>::min();
     constexpr auto hiVal = std::numeric_limits<To>::max();
 
-    if (std::is_same<Ti, cl_half>::value)
-    {
     cl_float f = cl_half_to_float(lhs) * cl_half_to_float(rhs);
 
     // Quantize to fp16:
     f = cl_half_to_float(cl_half_from_float(f, half_rounding));
 
-        To val = (To)std::min<float>(std::max<float>(f, loVal), hiVal);
+    To val = static_cast<To>(std::min<float>(std::max<float>(f, loVal), hiVal));
     if (isnan(cl_half_to_float(rhs)))
     {
         val = 0;
     }
     return val;
-    }
+}
 
-    Tl ival = (Tl)(lhs * rhs);
-    To val = (To)std::min<Ti>(std::max<Ti>(ival, loVal), hiVal);
+template <typename Ti, typename Tl, typename To>
+static inline
+    typename std::enable_if<!std::is_same<Ti, cl_half>::value, To>::type
+    compute_saturated_output(Ti lhs, Ti rhs, cl_half_rounding_mode)
+{
+    constexpr auto loVal = std::numeric_limits<To>::min();
+    constexpr auto hiVal = std::numeric_limits<To>::max();
+
+    Tl ival = static_cast<Tl>(lhs * rhs);
+    To val = static_cast<To>(std::min<Tl>(std::max<Tl>(ival, loVal), hiVal));
 
     if (isnan(rhs))
     {