[llvm] [ADT, Support] Move llvm::numbers to STLForwardCompat.h (PR #164053)
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Fri Oct 17 23:54:06 PDT 2025
llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-llvm-adt
Author: Kazu Hirata (kazutakahirata)
<details>
<summary>Changes</summary>
This patch moves llvm::numbers to STLForwardCompat.h for those
constants defined in C++20 to facilitate the migration to C++20.
"float" constants like ef and pif are not part of C++20, so they stay
in MathExtras.h but are reimplemented in terms of e_v, pi_v, etc.
sqrtpi and sqrtpif are not part of C++20, so they also stay in
MathExtras.h, but they are redefined in terms of sqrtpi_v in the same
style as other constants.
I've verified the new C++17-style implementation to be bit-for-bit
identical to the original definitions using static_assert:
static_assert(e == llvm::numbers_new::e_v<double>);
static_assert(ef == llvm::numbers_new::e_v<float>);
before replacing the original definitions of e and ef in MathExtras.h,
where llvm::numbers_new was a namesapce I used in STLForwardCompat.h
for testing purposes.
---
Full diff: https://github.com/llvm/llvm-project/pull/164053.diff
2 Files Affected:
- (modified) llvm/include/llvm/ADT/STLForwardCompat.h (+48)
- (modified) llvm/include/llvm/Support/MathExtras.h (+22-31)
``````````diff
diff --git a/llvm/include/llvm/ADT/STLForwardCompat.h b/llvm/include/llvm/ADT/STLForwardCompat.h
index da9d3ab0e32a3..273a5cf8aa8ff 100644
--- a/llvm/include/llvm/ADT/STLForwardCompat.h
+++ b/llvm/include/llvm/ADT/STLForwardCompat.h
@@ -26,6 +26,54 @@ namespace llvm {
// Features from C++20
//===----------------------------------------------------------------------===//
+namespace numbers {
+// clang-format off
+template <typename T, typename = std::enable_if_t<std::is_floating_point_v<T>>>
+inline constexpr T e_v = T(0x1.5bf0a8b145769P+1); // (2.7182818284590452354) https://oeis.org/A001113
+template <typename T, typename = std::enable_if_t<std::is_floating_point_v<T>>>
+inline constexpr T egamma_v = T(0x1.2788cfc6fb619P-1); // (.57721566490153286061) https://oeis.org/A001620
+template <typename T, typename = std::enable_if_t<std::is_floating_point_v<T>>>
+inline constexpr T ln2_v = T(0x1.62e42fefa39efP-1); // (.69314718055994530942) https://oeis.org/A002162
+template <typename T, typename = std::enable_if_t<std::is_floating_point_v<T>>>
+inline constexpr T ln10_v = T(0x1.26bb1bbb55516P+1); // (2.3025850929940456840) https://oeis.org/A002392
+template <typename T, typename = std::enable_if_t<std::is_floating_point_v<T>>>
+inline constexpr T log2e_v = T(0x1.71547652b82feP+0); // (1.4426950408889634074)
+template <typename T, typename = std::enable_if_t<std::is_floating_point_v<T>>>
+inline constexpr T log10e_v = T(0x1.bcb7b1526e50eP-2); // (.43429448190325182765)
+template <typename T, typename = std::enable_if_t<std::is_floating_point_v<T>>>
+inline constexpr T pi_v = T(0x1.921fb54442d18P+1); // (3.1415926535897932385) https://oeis.org/A000796
+template <typename T, typename = std::enable_if_t<std::is_floating_point_v<T>>>
+inline constexpr T inv_pi_v = T(0x1.45f306dc9c883P-2); // (.31830988618379067154) https://oeis.org/A049541
+template <typename T, typename = std::enable_if_t<std::is_floating_point_v<T>>>
+inline constexpr T inv_sqrtpi_v = T(0x1.20dd750429b6dP-1); // (.56418958354775628695) https://oeis.org/A087197
+template <typename T, typename = std::enable_if_t<std::is_floating_point_v<T>>>
+inline constexpr T sqrt2_v = T(0x1.6a09e667f3bcdP+0); // (1.4142135623730950488) https://oeis.org/A00219
+template <typename T, typename = std::enable_if_t<std::is_floating_point_v<T>>>
+inline constexpr T inv_sqrt2_v = T(0x1.6a09e667f3bcdP-1); // (.70710678118654752440)
+template <typename T, typename = std::enable_if_t<std::is_floating_point_v<T>>>
+inline constexpr T sqrt3_v = T(0x1.bb67ae8584caaP+0); // (1.7320508075688772935) https://oeis.org/A002194
+template <typename T, typename = std::enable_if_t<std::is_floating_point_v<T>>>
+inline constexpr T inv_sqrt3_v = T(0x1.279a74590331cP-1); // (.57735026918962576451)
+template <typename T, typename = std::enable_if_t<std::is_floating_point_v<T>>>
+inline constexpr T phi_v = T(0x1.9e3779b97f4a8P+0); // (1.6180339887498948482) https://oeis.org/A001622
+
+inline constexpr double e = e_v<double>;
+inline constexpr double egamma = egamma_v<double>;
+inline constexpr double ln2 = ln2_v<double>;
+inline constexpr double ln10 = ln10_v<double>;
+inline constexpr double log2e = log2e_v<double>;
+inline constexpr double log10e = log10e_v<double>;
+inline constexpr double pi = pi_v<double>;
+inline constexpr double inv_pi = inv_pi_v<double>;
+inline constexpr double inv_sqrtpi = inv_sqrtpi_v<double>;
+inline constexpr double sqrt2 = sqrt2_v<double>;
+inline constexpr double inv_sqrt2 = inv_sqrt2_v<double>;
+inline constexpr double sqrt3 = sqrt3_v<double>;
+inline constexpr double inv_sqrt3 = inv_sqrt3_v<double>;
+inline constexpr double phi = phi_v<double>;
+// clang-format on
+} // namespace numbers
+
template <typename T>
struct remove_cvref // NOLINT(readability-identifier-naming)
{
diff --git a/llvm/include/llvm/Support/MathExtras.h b/llvm/include/llvm/Support/MathExtras.h
index c2716a9704563..412323354525b 100644
--- a/llvm/include/llvm/Support/MathExtras.h
+++ b/llvm/include/llvm/Support/MathExtras.h
@@ -13,6 +13,7 @@
#ifndef LLVM_SUPPORT_MATHEXTRAS_H
#define LLVM_SUPPORT_MATHEXTRAS_H
+#include "llvm/ADT/STLForwardCompat.h"
#include "llvm/ADT/bit.h"
#include "llvm/Support/Compiler.h"
#include <cassert>
@@ -42,38 +43,28 @@ using common_sint =
/// Mathematical constants.
namespace numbers {
-// TODO: Track C++20 std::numbers.
// clang-format off
-constexpr double e = 0x1.5bf0a8b145769P+1, // (2.7182818284590452354) https://oeis.org/A001113
- egamma = 0x1.2788cfc6fb619P-1, // (.57721566490153286061) https://oeis.org/A001620
- ln2 = 0x1.62e42fefa39efP-1, // (.69314718055994530942) https://oeis.org/A002162
- ln10 = 0x1.26bb1bbb55516P+1, // (2.3025850929940456840) https://oeis.org/A002392
- log2e = 0x1.71547652b82feP+0, // (1.4426950408889634074)
- log10e = 0x1.bcb7b1526e50eP-2, // (.43429448190325182765)
- pi = 0x1.921fb54442d18P+1, // (3.1415926535897932385) https://oeis.org/A000796
- inv_pi = 0x1.45f306dc9c883P-2, // (.31830988618379067154) https://oeis.org/A049541
- sqrtpi = 0x1.c5bf891b4ef6bP+0, // (1.7724538509055160273) https://oeis.org/A002161
- inv_sqrtpi = 0x1.20dd750429b6dP-1, // (.56418958354775628695) https://oeis.org/A087197
- sqrt2 = 0x1.6a09e667f3bcdP+0, // (1.4142135623730950488) https://oeis.org/A00219
- inv_sqrt2 = 0x1.6a09e667f3bcdP-1, // (.70710678118654752440)
- sqrt3 = 0x1.bb67ae8584caaP+0, // (1.7320508075688772935) https://oeis.org/A002194
- inv_sqrt3 = 0x1.279a74590331cP-1, // (.57735026918962576451)
- phi = 0x1.9e3779b97f4a8P+0; // (1.6180339887498948482) https://oeis.org/A001622
-constexpr float ef = 0x1.5bf0a8P+1F, // (2.71828183) https://oeis.org/A001113
- egammaf = 0x1.2788d0P-1F, // (.577215665) https://oeis.org/A001620
- ln2f = 0x1.62e430P-1F, // (.693147181) https://oeis.org/A002162
- ln10f = 0x1.26bb1cP+1F, // (2.30258509) https://oeis.org/A002392
- log2ef = 0x1.715476P+0F, // (1.44269504)
- log10ef = 0x1.bcb7b2P-2F, // (.434294482)
- pif = 0x1.921fb6P+1F, // (3.14159265) https://oeis.org/A000796
- inv_pif = 0x1.45f306P-2F, // (.318309886) https://oeis.org/A049541
- sqrtpif = 0x1.c5bf8aP+0F, // (1.77245385) https://oeis.org/A002161
- inv_sqrtpif = 0x1.20dd76P-1F, // (.564189584) https://oeis.org/A087197
- sqrt2f = 0x1.6a09e6P+0F, // (1.41421356) https://oeis.org/A002193
- inv_sqrt2f = 0x1.6a09e6P-1F, // (.707106781)
- sqrt3f = 0x1.bb67aeP+0F, // (1.73205081) https://oeis.org/A002194
- inv_sqrt3f = 0x1.279a74P-1F, // (.577350269)
- phif = 0x1.9e377aP+0F; // (1.61803399) https://oeis.org/A001622
+inline constexpr float ef = e_v<float>;
+inline constexpr float egammaf = egamma_v<float>;
+inline constexpr float ln2f = ln2_v<float>;
+inline constexpr float ln10f = ln10_v<float>;
+inline constexpr float log2ef = log2e_v<float>;
+inline constexpr float log10ef = log10e_v<float>;
+inline constexpr float pif = pi_v<float>;
+inline constexpr float inv_pif = inv_pi_v<float>;
+inline constexpr float inv_sqrtpif = inv_sqrtpi_v<float>;
+inline constexpr float sqrt2f = sqrt2_v<float>;
+inline constexpr float inv_sqrt2f = inv_sqrt2_v<float>;
+inline constexpr float sqrt3f = sqrt3_v<float>;
+inline constexpr float inv_sqrt3f = inv_sqrt3_v<float>;
+inline constexpr float phif = phi_v<float>;
+
+// sqrtpi is not in C++20 std::numbers.
+template <typename T, typename = std::enable_if_t<std::is_floating_point_v<T>>>
+inline constexpr T sqrtpi_v = T(0x1.c5bf891b4ef6bP+0); // (1.7724538509055160273) https://oeis.org/A002161
+inline constexpr double sqrtpi = sqrtpi_v<double>;
+inline constexpr float sqrtpif = sqrtpi_v<float>;
+
// These string literals are taken from below:
// https://github.com/bminor/glibc/blob/8543577b04ded6d979ffcc5a818930e4d74d0645/math/math.h#L1215-L1229
constexpr const char *pis = "3.141592653589793238462643383279502884",
``````````
</details>
https://github.com/llvm/llvm-project/pull/164053
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