[Libclc-dev] [PATCH 2/2] AMDGPU: Implement accurate double precision sqrt

[Tom Stellard]

---
 amdgcn/lib/SOURCES      |  1 +
 amdgcn/lib/math/sqrt.cl | 59 +++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 60 insertions(+)
 create mode 100644 amdgcn/lib/SOURCES
 create mode 100644 amdgcn/lib/math/sqrt.cl

diff --git a/amdgcn/lib/SOURCES b/amdgcn/lib/SOURCES
new file mode 100644
index 0000000..64f874c
--- /dev/null
+++ b/amdgcn/lib/SOURCES
@@ -0,0 +1 @@
+math/sqrt.cl
diff --git a/amdgcn/lib/math/sqrt.cl b/amdgcn/lib/math/sqrt.cl
new file mode 100644
index 0000000..3e5b17c
--- /dev/null
+++ b/amdgcn/lib/math/sqrt.cl
@@ -0,0 +1,59 @@
+/*
+ * Copyright (c) 2015 Advanced Micro Devices, Inc.
+ *
+ * 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.
+ */
+
+#include <clc/clc.h>
+#include "../../../generic/lib/clcmacro.h"
+#include "math/clc_sqrt.h"
+
+_CLC_DEFINE_UNARY_BUILTIN(float, sqrt, __clc_sqrt, float)
+
+#ifdef cl_khr_fp64
+
+#pragma OPENCL EXTENSION cl_khr_fp64 : enable
+
+
+_CLC_OVERLOAD _CLC_DEF double sqrt(double x) {
+
+  uint vcc = x < 0x1p-767;
+  uint exp0 = vcc ? 0x100 : 0;
+  unsigned exp1 = vcc ? 0xffffff80 : 0;
+
+  double v01 = ldexp(x, exp0);
+  double v23 = __builtin_amdgpu_rsq(v01);
+  double v45 = v01 * v23;
+  v23 = v23 * 0.5;
+
+  double v67 = fma(-v23, v45, 0.5);
+  v45 = fma(v45, v67, v45);
+  double v89 = fma(-v45, v45, v01);
+  v23 = fma(v23, v67, v23);
+  v45 = fma(v89, v23, v45);
+  v67 = fma(-v45, v45, v01);
+  v23 = fma(v67, v23, v45);
+
+  v23 = ldexp(v23, exp1);
+  return ((x == __builtin_inf()) || (x == 0.0)) ? v01 : v23;
+}
+
+_CLC_UNARY_VECTORIZE(_CLC_OVERLOAD _CLC_DEF, double, sqrt, double);
+
+#endif
-- 
2.0.4