[libc][math] Refactor exp implementation to header-only in src/__support/math folder. (#148761)

- **[libc][math] Refactor exp implementation to header-only in
src/__support/math folder.**
- **Reapply "[libc][math] Refactor exp implementation to header-only in
src/__support/math folder." (#148668)**

Author: bassiounix

libc/shared/math.h

@@ -11,6 +11,7 @@
 
 #include "libc_common.h"
 
+#include "math/exp.h"
 #include "math/expf.h"
 #include "math/expf16.h"
 #include "math/frexpf.h"

libc/shared/math/exp.h

@@ -0,0 +1,23 @@
+//===-- Shared exp 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_EXP_H
+#define LLVM_LIBC_SHARED_MATH_EXP_H
+
+#include "shared/libc_common.h"
+#include "src/__support/math/exp.h"
+
+namespace LIBC_NAMESPACE_DECL {
+namespace shared {
+
+using math::exp;
+
+} // namespace shared
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SHARED_MATH_EXP_H

libc/src/__support/FPUtil/multiply_add.h

@@ -29,7 +29,7 @@ multiply_add(const T &x, const T &y, const T &z) {
 }
 
 template <typename T>
-LIBC_INLINE cpp::enable_if_t<(sizeof(T) <= sizeof(void *)), T>
+LIBC_INLINE static constexpr cpp::enable_if_t<(sizeof(T) <= sizeof(void *)), T>
 multiply_add(T x, T y, T z) {
   return x * y + z;
 }

libc/src/__support/FPUtil/nearest_integer.h

@@ -40,7 +40,7 @@ namespace fputil {
 // Notice that for AARCH64 and x86-64 with SSE4.2 support, we will use their
 // corresponding rounding instruction instead.  And in those cases, the results
 // are rounded to the nearest integer, tie-to-even.
-LIBC_INLINE float nearest_integer(float x) {
+LIBC_INLINE static constexpr float nearest_integer(float x) {
   if (x < 0x1p24f && x > -0x1p24f) {
     float r = x < 0 ? (x - 0x1.0p23f) + 0x1.0p23f : (x + 0x1.0p23f) - 0x1.0p23f;
     float diff = x - r;
@@ -56,7 +56,7 @@ LIBC_INLINE float nearest_integer(float x) {
   return x;
 }
 
-LIBC_INLINE double nearest_integer(double x) {
+LIBC_INLINE static constexpr double nearest_integer(double x) {
   if (x < 0x1p53 && x > -0x1p53) {
     double r = x < 0 ? (x - 0x1.0p52) + 0x1.0p52 : (x + 0x1.0p52) - 0x1.0p52;
     double diff = x - r;

libc/src/__support/math/CMakeLists.txt

@@ -110,3 +110,42 @@ add_header_library(
   DEPENDS
     libc.src.__support.FPUtil.manipulation_functions
 )
+
+add_header_library(
+  exp_constants
+  HDRS
+    exp_constants.h
+  DEPENDS
+    libc.src.__support.FPUtil.triple_double
+)
+
+add_header_library(
+  exp_utils
+  HDRS
+    exp_utils.h
+  DEPENDS
+    libc.src.__support.CPP.optional
+    libc.src.__support.CPP.bit
+    libc.src.__support.FPUtil.fp_bits
+)
+
+add_header_library(
+  exp
+  HDRS
+    exp.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
+)