[Beignet] [PATCH] libocl: refine implementation of sign().

[Ruiling Song]

Avoid if-branching.

Signed-off-by: Ruiling Song <ruiling.song at intel.com>
---
 backend/src/libocl/tmpl/ocl_common.tmpl.cl |   16 +++++++++-------
 1 file changed, 9 insertions(+), 7 deletions(-)

diff --git a/backend/src/libocl/tmpl/ocl_common.tmpl.cl b/backend/src/libocl/tmpl/ocl_common.tmpl.cl
index db7b0d8..77bd2d3 100644
--- a/backend/src/libocl/tmpl/ocl_common.tmpl.cl
+++ b/backend/src/libocl/tmpl/ocl_common.tmpl.cl
@@ -17,6 +17,7 @@
  */
 #include "ocl_common.h"
 #include "ocl_float.h"
+#include "ocl_relational.h"
 
 /////////////////////////////////////////////////////////////////////////////
 // Common Functions
@@ -55,11 +56,12 @@ OVERLOADABLE float smoothstep(float e0, float e1, float x) {
 }
 
 OVERLOADABLE float sign(float x) {
-  if(x > 0)
-    return 1;
-  if(x < 0)
-    return -1;
-  if(x == -0.f)
-    return -0.f;
-  return 0.f;
+  union {float f; unsigned u;} ieee;
+  ieee.f = x;
+  unsigned k = ieee.u;
+  float r = (k&0x80000000) ? -1.0f : 1.0f;
+  // differentiate +0.0f -0.0f
+  float s = 0.0f * r;
+  s = (x == 0.0f) ? s : r;
+  return isnan(x) ? 0.0f : s;
 }
-- 
1.7.10.4