Adding GELU activation

OpenCL implementation uses built in erf.

NEON implementation requires new vectorized erf.
Uses the following approximation:
erf(x) = 1 - 1 / (1 + a1x + a2x^2 + a3x^3 + a4x^4)^4
a1 = 0.278393, a2 = 0.230389, a3 = 0.000972, a4 = 0.078108

From https://en.wikipedia.org/wiki/Error_function#Numerical_approximations

Signed-off-by: Murray Kornelsen <murray.kornelsen@mail.mcgill.ca>
Change-Id: I2d3964b2c26a4334166b17135f9104bc6324fad2
Reviewed-on: https://review.mlplatform.org/c/ml/ComputeLibrary/+/7921
Reviewed-by: Viet-Hoa Do <viet-hoa.do@arm.com>
Reviewed-by: Pablo Marquez Tello <pablo.tello@arm.com>
Comments-Addressed: Arm Jenkins <bsgcomp@arm.com>
Comments-Addressed: Pablo Marquez Tello <pablo.tello@arm.com>
Tested-by: Arm Jenkins <bsgcomp@arm.com>
Benchmark: Arm Jenkins <bsgcomp@arm.com>

4 files changed, 119 insertions, 3 deletions

diff --git a/src/core/NEON/NEMath.h b/src/core/NEON/NEMath.h
index 8118c4701f..9e81c38ad8 100644
--- a/src/core/NEON/NEMath.h
+++ b/src/core/NEON/NEMath.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2016-2021 Arm Limited.
+ * Copyright (c) 2016-2022 Arm Limited.
  *
  * SPDX-License-Identifier: MIT
  *
@@ -94,6 +94,14 @@ float32x4_t vtaylor_polyq_f32(float32x4_t x, const std::array<float32x4_t, 8> &c
  */
 float32x4_t vexpq_f32(float32x4_t x);
 
+/** Calculate error function
+ *
+ * @param[in] x Input vector in F32 format.
+ *
+ * @return The calculated erf.
+ */
+float32x4_t verfq_f32(float32x4_t x);
+
 /** Calculate logarithm
  *
  * @param[in] x Input vector value in F32 format.
@@ -308,6 +316,14 @@ float16x8_t vinvsqrtq_f16(float16x8_t x);
  */
 float16x8_t vexpq_f16(float16x8_t x);
 
+/** Calculate error function
+ *
+ * @param[in] x Input vector in F16 format.
+ *
+ * @return The calculated erf.
+ */
+float16x8_t verfq_f16(float16x8_t x);
+
 /** Calculate n power of a number.
  *
  * pow(x,n) = e^(n*log(x))
diff --git a/src/core/NEON/NEMath.inl b/src/core/NEON/NEMath.inl
index 05cf3013bc..1b0b894153 100644
--- a/src/core/NEON/NEMath.inl
+++ b/src/core/NEON/NEMath.inl
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2016-2021 Arm Limited.
+ * Copyright (c) 2016-2022 Arm Limited.
  *
  * SPDX-License-Identifier: MIT
  *
@@ -166,6 +166,43 @@ inline float32x4_t vexpq_f32(float32x4_t x)
     return poly;
 }
 
+#ifdef __aarch64__
+inline float32x4_t verfq_f32(float32x4_t x)
+{
+    static const float       erffdata[4] = { 0.278393f, 0.230389f, 0.000972f, 0.078108f };
+    static const float32x4_t coeffdata   = vld1q_f32(erffdata);
+    static const float32x4_t onev{ vdupq_n_f32(1.0f) };
+
+    uint32x4_t selector = vcltzq_f32(x);
+
+    float32x4_t absx  = vabsq_f32(x);
+    float32x4_t absx2 = vmulq_f32(x, x);
+    float32x4_t absx3 = vmulq_f32(absx2, absx);
+    float32x4_t absx4 = vmulq_f32(absx2, absx2);
+
+    float32x4_t denom = onev;
+    denom             = vfmaq_laneq_f32(denom, absx, coeffdata, 0);
+    denom             = vfmaq_laneq_f32(denom, absx2, coeffdata, 1);
+    denom             = vfmaq_laneq_f32(denom, absx3, coeffdata, 2);
+    denom             = vfmaq_laneq_f32(denom, absx4, coeffdata, 3);
+
+    denom = vmulq_f32(denom, denom);
+    denom = vmulq_f32(denom, denom);
+
+    float32x4_t fract = onev;
+    fract             = vdivq_f32(fract, denom);
+
+    float32x4_t result = onev;
+    result             = vsubq_f32(result, fract);
+
+    float32x4_t inverse = vnegq_f32(result);
+
+    result = vbslq_f32(selector, inverse, result);
+
+    return result;
+}
+#endif // #ifdef __aarch64__
+
 inline float32x4_t vlogq_f32(float32x4_t x)
 {
     static const int32x4_t   CONST_127 = vdupq_n_s32(127);           // 127
@@ -517,6 +554,17 @@ inline float16x8_t vexpq_f16(float16x8_t x)
     return res;
 }
 
+#ifdef __aarch64__
+inline float16x8_t verfq_f16(float16x8_t x)
+{
+    const float32x4_t x_high = vcvt_f32_f16(vget_high_f16(x));
+    const float32x4_t x_low  = vcvt_f32_f16(vget_low_f16(x));
+
+    const float16x8_t res = vcombine_f16(vcvt_f16_f32(verfq_f32(x_low)), vcvt_f16_f32(verfq_f32(x_high)));
+    return res;
+}
+#endif // #ifdef __aarch64__
+
 inline float16x8_t vlogq_f16(float16x8_t x)
 {
     const float32x4_t x_high = vcvt_f32_f16(vget_high_f16(x));
diff --git a/src/core/NEON/wrapper/intrinsics/erf.h b/src/core/NEON/wrapper/intrinsics/erf.h
new file mode 100644
index 0000000000..e2207648e5
--- /dev/null
+++ b/src/core/NEON/wrapper/intrinsics/erf.h
@@ -0,0 +1,51 @@
+/*
+ * Copyright (c) 2022 Arm Limited.
+ *
+ * SPDX-License-Identifier: MIT
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to
+ * deal in the Software without restriction, including without limitation the
+ * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
+ * sell copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#ifndef ARM_COMPUTE_WRAPPER_ERF_H
+#define ARM_COMPUTE_WRAPPER_ERF_H
+
+#include "src/core/NEON/NEMath.h"
+#include <arm_neon.h>
+
+namespace arm_compute
+{
+namespace wrapper
+{
+#define VERF_IMPL(vtype, prefix, postfix) \
+    inline vtype verf(const vtype &a)     \
+    {                                     \
+        return prefix##_##postfix(a);     \
+    }
+
+VERF_IMPL(float32x4_t, verfq, f32)
+#ifdef __ARM_FEATURE_FP16_VECTOR_ARITHMETIC
+VERF_IMPL(float16x8_t, verfq, f16)
+#endif // __ARM_FEATURE_FP16_VECTOR_ARITHMETIC
+
+#undef VERF_IMPL
+
+} // namespace wrapper
+} // namespace arm_compute
+
+#endif /* ARM_COMPUTE_WRAPPER_ERF_H */
diff --git a/src/core/NEON/wrapper/intrinsics/intrinsics.h b/src/core/NEON/wrapper/intrinsics/intrinsics.h
index 871d9cc5ac..0256e0a8c8 100644
--- a/src/core/NEON/wrapper/intrinsics/intrinsics.h
+++ b/src/core/NEON/wrapper/intrinsics/intrinsics.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2018-2021 Arm Limited.
+ * Copyright (c) 2018-2022 Arm Limited.
  *
  * SPDX-License-Identifier: MIT
  *
@@ -39,6 +39,7 @@
 #include "src/core/NEON/wrapper/intrinsics/div.h"
 #include "src/core/NEON/wrapper/intrinsics/dup_n.h"
 #include "src/core/NEON/wrapper/intrinsics/eor.h"
+#include "src/core/NEON/wrapper/intrinsics/erf.h"
 #include "src/core/NEON/wrapper/intrinsics/exp.h"
 #include "src/core/NEON/wrapper/intrinsics/ext.h"
 #include "src/core/NEON/wrapper/intrinsics/gethigh.h"