[libc][math] Refactor exp10 implementation to header-only in src/__support/math folder. (#148400)

Part of #147386

in preparation for:
https://discourse.llvm.org/t/rfc-make-clang-builtin-math-functions-constexpr-with-llvm-libc-to-support-c-23-constexpr-math-functions/86450

Author: bassiounix

libc/shared/math.h

@@ -12,6 +12,7 @@
 #include "libc_common.h"
 
 #include "math/exp.h"
+#include "math/exp10.h"
 #include "math/expf.h"
 #include "math/expf16.h"
 #include "math/frexpf.h"

libc/shared/math/exp10.h

@@ -0,0 +1,23 @@
+//===-- Shared exp10 function -----------------------------------*- C++ -*-===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SHARED_MATH_EXP10_H
+#define LLVM_LIBC_SHARED_MATH_EXP10_H
+
+#include "shared/libc_common.h"
+#include "src/__support/math/exp10.h"
+
+namespace LIBC_NAMESPACE_DECL {
+namespace shared {
+
+using math::exp10;
+
+} // namespace shared
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SHARED_MATH_EXP10_H

libc/src/__support/FPUtil/PolyEval.h

@@ -37,7 +37,7 @@ LIBC_INLINE cpp::enable_if_t<(sizeof(T) <= sizeof(void *)), T> polyeval(T,
 }
 
 template <typename T, typename... Ts>
-LIBC_INLINE cpp::enable_if_t<(sizeof(T) > sizeof(void *)), T>
+LIBC_INLINE static constexpr cpp::enable_if_t<(sizeof(T) > sizeof(void *)), T>
 polyeval(const T &x, const T &a0, const Ts &...a) {
   return multiply_add(x, polyeval(x, a...), a0);
 }

libc/src/__support/FPUtil/double_double.h

@@ -151,8 +151,8 @@ LIBC_INLINE DoubleDouble quick_mult(double a, const DoubleDouble &b) {
 }
 
 template <size_t SPLIT_B = 27>
-LIBC_INLINE DoubleDouble quick_mult(const DoubleDouble &a,
-                                    const DoubleDouble &b) {
+LIBC_INLINE constexpr DoubleDouble quick_mult(const DoubleDouble &a,
+                                              const DoubleDouble &b) {
   DoubleDouble r = exact_mult<double, SPLIT_B>(a.hi, b.hi);
   double t1 = multiply_add(a.hi, b.lo, r.lo);
   double t2 = multiply_add(a.lo, b.hi, t1);

libc/src/__support/math/CMakeLists.txt

@@ -149,3 +149,24 @@ add_header_library(
     libc.src.__support.integer_literals
     libc.src.__support.macros.optimization
 )
+
+add_header_library(
+  exp10
+  HDRS
+    exp10.h
+  DEPENDS
+    .exp_constants
+    .exp_utils
+    libc.src.__support.CPP.bit
+    libc.src.__support.CPP.optional
+    libc.src.__support.FPUtil.dyadic_float
+    libc.src.__support.FPUtil.fenv_impl
+    libc.src.__support.FPUtil.fp_bits
+    libc.src.__support.FPUtil.multiply_add
+    libc.src.__support.FPUtil.nearest_integer
+    libc.src.__support.FPUtil.polyeval
+    libc.src.__support.FPUtil.rounding_mode
+    libc.src.__support.FPUtil.triple_double
+    libc.src.__support.integer_literals
+    libc.src.__support.macros.optimization
+)