[Beignet] [PATCH 1/2] GBE: fix some builtin math function

[Ruiling Song]

__gen_ocl_exp stands for 2^x. So, use __gen_ocl_pow to implement native_exp().
Fix atanh implementation.

Signed-off-by: Ruiling Song <ruiling.song at intel.com>
---
 backend/src/ocl_stdlib.tmpl.h |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/backend/src/ocl_stdlib.tmpl.h b/backend/src/ocl_stdlib.tmpl.h
index fc6de25..6836de4 100755
--- a/backend/src/ocl_stdlib.tmpl.h
+++ b/backend/src/ocl_stdlib.tmpl.h
@@ -2258,8 +2258,8 @@ INLINE_OVERLOADABLE float native_tan(float x) {
 INLINE_OVERLOADABLE float __gen_ocl_internal_tanpi(float x) {
   return native_tan(x * M_PI_F);
 }
-INLINE_OVERLOADABLE float native_exp(float x) { return __gen_ocl_exp(x); }
-INLINE_OVERLOADABLE float native_exp2(float x) { return __gen_ocl_pow(2, x); }
+INLINE_OVERLOADABLE float native_exp2(float x) { return __gen_ocl_exp(x); }
+INLINE_OVERLOADABLE float native_exp(float x) { return __gen_ocl_pow(M_E_F, x); }
 INLINE_OVERLOADABLE float native_exp10(float x) { return __gen_ocl_pow(10, x); }
 INLINE_OVERLOADABLE float __gen_ocl_internal_cbrt(float x) {
   /* copied from fdlibm */
@@ -4863,7 +4863,7 @@ INLINE_OVERLOADABLE float __gen_ocl_internal_fastpath_asinh (float x)
 
 INLINE_OVERLOADABLE float __gen_ocl_internal_fastpath_atanh (float x)
 {
-    return 0.5f * native_sqrt((1 + x) / (1 - x));
+    return 0.5f * native_log((1 + x) / (1 - x));
 }
 
 INLINE_OVERLOADABLE float __gen_ocl_internal_fastpath_cbrt (float x)
-- 
1.7.10.4