[libc-commits] [libc] [libc][math][c23] Add exp10f16 C23 math function (PR #101588)

[via libc-commits]

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@@ -0,0 +1,177 @@
+//===-- Half-precision 10^x function --------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/math/exp10f16.h"
+#include "hdr/errno_macros.h"
+#include "hdr/fenv_macros.h"
+#include "src/__support/CPP/array.h"
+#include "src/__support/FPUtil/FEnvImpl.h"
+#include "src/__support/FPUtil/FPBits.h"
+#include "src/__support/FPUtil/PolyEval.h"
+#include "src/__support/FPUtil/except_value_utils.h"
+#include "src/__support/FPUtil/multiply_add.h"
+#include "src/__support/FPUtil/nearest_integer.h"
+#include "src/__support/FPUtil/rounding_mode.h"
+#include "src/__support/common.h"
+#include "src/__support/macros/config.h"
+#include "src/__support/macros/optimization.h"
+#include "src/__support/macros/properties/cpu_features.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+static constexpr size_t N_EXP10F16_EXCEPTS = 5
+#ifndef LIBC_TARGET_CPU_HAS_FMA
+                                             + 3
+#endif
+    ;
+
+static constexpr fputil::ExceptValues<float16, N_EXP10F16_EXCEPTS>
+    EXP10F16_EXCEPTS = {{
+        // x = 0x1.8f4p-2, exp10f16(x) = 0x1.3ap+1 (RZ)
+        {0x363dU, 0x40e8U, 1U, 0U, 1U},
+        // x = 0x1.95cp-2, exp10f16(x) = 0x1.3ecp+1 (RZ)
+        {0x3657U, 0x40fbU, 1U, 0U, 0U},
+        // x = -0x1.018p-4, exp10f16(x) = 0x1.bbp-1 (RZ)
+        {0xac06U, 0x3aecU, 1U, 0U, 0U},
+        // x = -0x1.c28p+0, exp10f16(x) = 0x1.1ccp-6 (RZ)
+        {0xbf0aU, 0x2473U, 1U, 0U, 0U},
+        // x = -0x1.e1cp+1, exp10f16(x) = 0x1.694p-13 (RZ)
+        {0xc387U, 0x09a5U, 1U, 0U, 0U},
+#ifndef LIBC_TARGET_CPU_HAS_FMA
+        // x = 0x1.0cp+1, exp10f16(x) = 0x1.f04p+6 (RZ)
+        {0x4030U, 0x57c1U, 1U, 0U, 1U},
+        // x = 0x1.1b8p+1, exp10f16(x) = 0x1.47cp+7 (RZ)
+        {0x406eU, 0x591fU, 1U, 0U, 1U},
+        // x = 0x1.1b8p+2, exp10f16(x) = 0x1.a4p+14 (RZ)
+        {0x446eU, 0x7690U, 1U, 0U, 1U},
+#endif
+    }};
+
+// Generated by Sollya with the following commands:
+//   > display = hexadecimal;
+//   > round(log2(10), SG, RN);
+static constexpr float LOG2F_10 = 0x1.a934fp+1f;
+
+// Generated by Sollya with the following commands:
+//   > display = hexadecimal;
+//   > round(log10(2), SG, RN);
+static constexpr float LOG10F_2 = 0x1.344136p-2f;
+
+// Generated by Sollya with the following commands:
+//   > display = hexadecimal;
+//   > for i from 0 to 7 do printsingle(round(2^(i * 2^-3), SG, RN));
+static constexpr cpp::array<uint32_t, 8> EXP2_MID_BITS = {
+    0x3f80'0000U, 0x3f8b'95c2U, 0x3f98'37f0U, 0x3fa5'fed7U,
+    0x3fb5'04f3U, 0x3fc5'672aU, 0x3fd7'44fdU, 0x3fea'c0c7U,
+};
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overmighty wrote:

Copy-pasted from exp2f16.cpp. I guess I should create a shared expxf16.h header instead.

https://github.com/llvm/llvm-project/pull/101588