[Beignet] [PATCH] fix isnan (builtin function)

[Homer Hsing]

this patch passes following piglit test case
  piglit/framework/../bin/cl-program-tester generated_tests/cl/builtin/relational/builtin-float-isnan-1.0.generated.cl

Signed-off-by: Homer Hsing <homer.xing at intel.com>
---
 backend/src/ocl_stdlib.tmpl.h | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/backend/src/ocl_stdlib.tmpl.h b/backend/src/ocl_stdlib.tmpl.h
index 8dfea09..831a658 100644
--- a/backend/src/ocl_stdlib.tmpl.h
+++ b/backend/src/ocl_stdlib.tmpl.h
@@ -246,7 +246,11 @@ DEF(uint, float);
 
 INLINE_OVERLOADABLE int isfinite(float x) { return __builtin_isfinite(x); }
 INLINE_OVERLOADABLE int isinf(float x) { return __builtin_isinf(x); }
-INLINE_OVERLOADABLE int isnan(float x) { return __builtin_isnan(x); }
+INLINE_OVERLOADABLE int isnan(float x) {
+  union { uint u; float f; } u;
+  u.f = x;
+  return (u.u & 0x7FFFFFFF) > 0x7F800000;
+}
 INLINE_OVERLOADABLE int isnormal(float x) { return __builtin_isnormal(x); }
 INLINE_OVERLOADABLE int isordered(float x, float y) { return isequal(x, x) && isequal(y, y); }
 INLINE_OVERLOADABLE int isunordered(float x, float y) { return isnan(x) || isnan(y); }
-- 
1.8.1.2