[libcxx-commits] [libcxx] [libc++] Avoid including <cmath> in <compare> (PR #80418)

[Nikolas Klauser via libcxx-commits]

https://github.com/philnik777 created https://github.com/llvm/llvm-project/pull/80418

This reduces the time to include `<compare>` from 84ms to 36ms.


>From 70e9feb35f415f9afb0901fb9697e19f69bdcf72 Mon Sep 17 00:00:00 2001
From: Nikolas Klauser <nikolasklauser at berlin.de>
Date: Fri, 2 Feb 2024 12:56:58 +0100
Subject: [PATCH] [libc++] Avoid including <cmath> in <compare>

---
 libcxx/include/__compare/strong_order.h | 21 +++++++++++----------
 libcxx/include/__compare/weak_order.h   | 10 +++++-----
 2 files changed, 16 insertions(+), 15 deletions(-)

diff --git a/libcxx/include/__compare/strong_order.h b/libcxx/include/__compare/strong_order.h
index 5f6ade5aef8e4..7acc774dd4988 100644
--- a/libcxx/include/__compare/strong_order.h
+++ b/libcxx/include/__compare/strong_order.h
@@ -13,11 +13,12 @@
 #include <__compare/compare_three_way.h>
 #include <__compare/ordering.h>
 #include <__config>
+#include <__math/exponential_functions.h>
+#include <__math/traits.h>
 #include <__type_traits/conditional.h>
 #include <__type_traits/decay.h>
 #include <__utility/forward.h>
 #include <__utility/priority_tag.h>
-#include <cmath>
 #include <cstdint>
 #include <limits>
 
@@ -66,27 +67,27 @@ struct __fn {
       return strong_ordering::greater;
     } else if (__t == __u) {
       if constexpr (numeric_limits<_Dp>::radix == 2) {
-        return std::signbit(__u) <=> std::signbit(__t);
+        return __math::signbit(__u) <=> __math::signbit(__t);
       } else {
         // This is bullet 3 of the IEEE754 algorithm, relevant
         // only for decimal floating-point;
         // see https://stackoverflow.com/questions/69068075/
-        if (__t == 0 || std::isinf(__t)) {
-          return std::signbit(__u) <=> std::signbit(__t);
+        if (__t == 0 || __math::isinf(__t)) {
+          return __math::signbit(__u) <=> __math::signbit(__t);
         } else {
           int __texp, __uexp;
-          (void)std::frexp(__t, &__texp);
-          (void)std::frexp(__u, &__uexp);
+          (void)__math::frexp(__t, &__texp);
+          (void)__math::frexp(__u, &__uexp);
           return (__t < 0) ? (__texp <=> __uexp) : (__uexp <=> __texp);
         }
       }
     } else {
       // They're unordered, so one of them must be a NAN.
       // The order is -QNAN, -SNAN, numbers, +SNAN, +QNAN.
-      bool __t_is_nan      = std::isnan(__t);
-      bool __u_is_nan      = std::isnan(__u);
-      bool __t_is_negative = std::signbit(__t);
-      bool __u_is_negative = std::signbit(__u);
+      bool __t_is_nan      = __math::isnan(__t);
+      bool __u_is_nan      = __math::isnan(__u);
+      bool __t_is_negative = __math::signbit(__t);
+      bool __u_is_negative = __math::signbit(__u);
       using _IntType =
           conditional_t< sizeof(__t) == sizeof(int32_t),
                          int32_t,
diff --git a/libcxx/include/__compare/weak_order.h b/libcxx/include/__compare/weak_order.h
index 9f719eb64bbca..1f7a9a6927659 100644
--- a/libcxx/include/__compare/weak_order.h
+++ b/libcxx/include/__compare/weak_order.h
@@ -13,10 +13,10 @@
 #include <__compare/ordering.h>
 #include <__compare/strong_order.h>
 #include <__config>
+#include <__math/traits.h>
 #include <__type_traits/decay.h>
 #include <__utility/forward.h>
 #include <__utility/priority_tag.h>
-#include <cmath>
 
 #ifndef _LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER
 #  pragma GCC system_header
@@ -51,10 +51,10 @@ struct __fn {
       return weak_ordering::greater;
     } else {
       // Otherwise, at least one of them is a NaN.
-      bool __t_is_nan      = std::isnan(__t);
-      bool __u_is_nan      = std::isnan(__u);
-      bool __t_is_negative = std::signbit(__t);
-      bool __u_is_negative = std::signbit(__u);
+      bool __t_is_nan      = __math::isnan(__t);
+      bool __u_is_nan      = __math::isnan(__u);
+      bool __t_is_negative = __math::signbit(__t);
+      bool __u_is_negative = __math::signbit(__u);
       if (__t_is_nan && __u_is_nan) {
         return (__u_is_negative <=> __t_is_negative);
       } else if (__t_is_nan) {