[Beignet] [PATCH 1/2] Handle edge and illegal values.

[Yi Sun]

Such as |x| = 1.0, |x| < 2**-27 and |x| > 1.

Signed-off-by: Yi Sun <yi.sun at intel.com>
---
 backend/src/ocl_stdlib.tmpl.h |   35 +++++++++++++++++++++++++++++++++++
 1 files changed, 35 insertions(+), 0 deletions(-)

diff --git a/backend/src/ocl_stdlib.tmpl.h b/backend/src/ocl_stdlib.tmpl.h
index 84f15ca..899a085 100644
--- a/backend/src/ocl_stdlib.tmpl.h
+++ b/backend/src/ocl_stdlib.tmpl.h
@@ -561,7 +561,42 @@ INLINE_OVERLOADABLE float __gen_ocl_internal_tanh(float x) {
   float y = native_exp(-2 * x);
   return (1 - y) / (1 + y);
 }
+
+typedef union
+{
+  float value;
+  int word;
+} ieee_float_shape_type;
+
+#ifndef GET_FLOAT_WORD
+# define GET_FLOAT_WORD(i,d)        \
+do {                                \
+  ieee_float_shape_type gf_u;       \
+  gf_u.value = (d);                 \
+  (i) = gf_u.word;                  \
+} while (0)
+#endif
+
+const float
+one =  1.0000000000e+00, /* 0x3F800000 */
+huge =  1.000e+30,
+pio2_hi = 1.57079637050628662109375f,
+pio2_lo = -4.37113900018624283e-8f;
+
 INLINE_OVERLOADABLE float __gen_ocl_internal_asin(float x) {
+  int hx, ix;
+  GET_FLOAT_WORD(hx,x);
+  ix = hx&0x7fffffff;
+  if(ix == 0x3f800000) {
+    return x*pio2_hi + x*pio2_lo;  /* asin(1)=+-pi/2 with inexact */
+  }
+  if(ix > 0x3f800000) {            /* |x|>= 1 */
+    return (x-x) / (x-x);          /* asin(|x|>1) is NaN */
+  }
+  if(ix < 0x32000000) {            /* if |x| < 2**-27 */
+    if(huge + x > one) return x;   /* return x with inexact if x!=0*/
+  }
+  /* 1 > |x| >= 2**-27 */
   float sum = x, c = x, m = 1.0;
   int n = 1;
   do
-- 
1.7.6.4