[libc][math] Refactor cospif implementation to header-only in src/__support/math folder. #154215

bassiounix · 2025-08-18T22:37:54Z

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

bassiounix · 2025-08-18T22:38:27Z

[libc][math] Refactor dsqrtl implementation to header-only in src/__support/math folder. #154868
[libc][math] Refactor cospif16 implementation to header-only in src/__support/math folder. #154222
[libc][math] Refactor cospif implementation to header-only in src/__support/math folder. #154215 👈 (View in Graphite)
[libc][math] Refactor coshf16 implementation to header-only in src/__support/math folder. #153582
[libc][math] Refactor coshf implementation to header-only in src/__support/math folder. #153427
[libc][math] Refactor cosf16 implementation to header-only in src/__support/math folder. #152871
[libc][math] Refactor cosf implementation to header-only in src/__support/math folder. #152069
[libc][math] Refactor cos implementation to header-only in src/__support/math folder. #151883
[libc][math] Refactor cbrtf implementation to header-only in src/__support/math folder. #151846
[libc][math] Refactor cbrt implementation to header-only in src/__support/math folder. #151837
[libc][math] Refactor atanhf16 implementation to header-only in src/__support/math folder. #151779
[libc][math] Refactor atanhf implementation to header-only in src/__support/math folder. #151399
[libc][math] Refactor atan2f128 implementation to header-only in src/__support/math folder. #151012
[libc][math] Refactor atan2f implementation to header-only in src/__support/math folder. #150993
[libc][math] Refactor atan2 implementation to header-only in src/__support/math folder. #150968
[libc][math] Refactor atanf16 implementation to header-only in src/__support/math folder. #150868
[libc][math] Refactor atanf implementation to header-only in src/__support/math folder. #150854
[libc][math] Refactor atan implementation to header-only in src/__support/math folder. #150852
[libc][math] Refactor asinhf16 implementation to header-only in src/__support/math folder. #150849
[libc][math] Refactor asinhf implementation to header-only in src/__support/math folder. #150843
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llvmbot · 2025-08-18T22:38:44Z

@llvm/pr-subscribers-libc

Author: Muhammad Bassiouni (bassiounix)

Changes

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

Full diff: https://github.com/llvm/llvm-project/pull/154215.diff

9 Files Affected:

(modified) libc/shared/math.h (+1)
(added) libc/shared/math/cospif.h (+23)
(modified) libc/src/__support/math/CMakeLists.txt (+12)
(added) libc/src/__support/math/cospif.h (+109)
(modified) libc/src/math/generic/CMakeLists.txt (+1-6)
(modified) libc/src/math/generic/cospif.cpp (+2-87)
(modified) libc/test/shared/CMakeLists.txt (+1)
(modified) libc/test/shared/shared_math_test.cpp (+1)
(modified) utils/bazel/llvm-project-overlay/libc/BUILD.bazel (+16-8)

diff --git a/libc/shared/math.h b/libc/shared/math.h
index a89aa90ee1ef8..6ab5df103bfb3 100644
--- a/libc/shared/math.h
+++ b/libc/shared/math.h
@@ -37,6 +37,7 @@
 #include "math/cosf16.h"
 #include "math/coshf.h"
 #include "math/coshf16.h"
+#include "math/cospif.h"
 #include "math/erff.h"
 #include "math/exp.h"
 #include "math/exp10.h"
diff --git a/libc/shared/math/cospif.h b/libc/shared/math/cospif.h
new file mode 100644
index 0000000000000..ce664e9c54859
--- /dev/null
+++ b/libc/shared/math/cospif.h
@@ -0,0 +1,23 @@
+//===-- Shared cospif 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_COSPIF_H
+#define LLVM_LIBC_SHARED_MATH_COSPIF_H
+
+#include "shared/libc_common.h"
+#include "src/__support/math/cospif.h"
+
+namespace LIBC_NAMESPACE_DECL {
+namespace shared {
+
+using math::cospif;
+
+} // namespace shared
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SHARED_MATH_COSPIF_H
diff --git a/libc/src/__support/math/CMakeLists.txt b/libc/src/__support/math/CMakeLists.txt
index cddf336369973..8ce6cef732d76 100644
--- a/libc/src/__support/math/CMakeLists.txt
+++ b/libc/src/__support/math/CMakeLists.txt
@@ -432,6 +432,18 @@ add_header_library(
     libc.src.__support.macros.optimization
 )
 
+add_header_library(
+  cospif
+  HDRS
+    cospif.h
+  DEPENDS
+    .sincosf_utils
+    libc.src.__support.FPUtil.fenv_impl
+    libc.src.__support.FPUtil.fp_bits
+    libc.src.__support.FPUtil.multiply_add
+    libc.src.__support.macros.optimization
+)
+
 add_header_library(
   erff
   HDRS
diff --git a/libc/src/__support/math/cospif.h b/libc/src/__support/math/cospif.h
new file mode 100644
index 0000000000000..e921090459769
--- /dev/null
+++ b/libc/src/__support/math/cospif.h
@@ -0,0 +1,109 @@
+//===-- Implementation header for cospif ------------------------*- 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_SRC___SUPPORT_MATH_COSPIF_H
+#define LLVM_LIBC_SRC___SUPPORT_MATH_COSPIF_H
+
+#include "sincosf_utils.h"
+#include "src/__support/FPUtil/FEnvImpl.h"
+#include "src/__support/FPUtil/FPBits.h"
+#include "src/__support/FPUtil/multiply_add.h"
+#include "src/__support/common.h"
+#include "src/__support/macros/config.h"
+#include "src/__support/macros/optimization.h"            // LIBC_UNLIKELY
+#include "src/__support/macros/properties/cpu_features.h" // LIBC_TARGET_CPU_HAS_FMA
+
+namespace LIBC_NAMESPACE_DECL {
+
+namespace math {
+
+LIBC_INLINE static constexpr float cospif(float x) {
+  using FPBits = typename fputil::FPBits<float>;
+
+  FPBits xbits(x);
+  xbits.set_sign(Sign::POS);
+
+  uint32_t x_abs = xbits.uintval();
+  double xd = static_cast<double>(xbits.get_val());
+
+  // Range reduction:
+  // For |x| > 1/32, we perform range reduction as follows:
+  // Find k and y such that:
+  //   x = (k + y) * 1/32
+  //   k is an integer
+  //   |y| < 0.5
+  //
+  // This is done by performing:
+  //   k = round(x * 32)
+  //   y = x * 32 - k
+  //
+  // Once k and y are computed, we then deduce the answer by the cosine of sum
+  // formula:
+  //   cospi(x) = cos((k + y)*pi/32)
+  //          = cos(y*pi/32) * cos(k*pi/32) - sin(y*pi/32) * sin(k*pi/32)
+  // The values of sin(k*pi/32) and cos(k*pi/32) for k = 0..63 are precomputed
+  // and stored using a vector of 32 doubles. Sin(y*pi/32) and cos(y*pi/32) are
+  // computed using degree-7 and degree-6 minimax polynomials generated by
+  // Sollya respectively.
+
+  // The exhautive test passes for smaller values
+  if (LIBC_UNLIKELY(x_abs < 0x38A2'F984U)) {
+
+#if defined(LIBC_TARGET_CPU_HAS_FMA_FLOAT)
+    return fputil::multiply_add(xbits.get_val(), -0x1.0p-25f, 1.0f);
+#else
+    return static_cast<float>(fputil::multiply_add(xd, -0x1.0p-25, 1.0));
+#endif // LIBC_TARGET_CPU_HAS_FMA_FLOAT
+  }
+
+  // Numbers greater or equal to 2^23 are always integers or NaN
+  if (LIBC_UNLIKELY(x_abs >= 0x4B00'0000)) {
+
+    if (LIBC_UNLIKELY(x_abs < 0x4B80'0000)) {
+      return (x_abs & 0x1) ? -1.0f : 1.0f;
+    }
+
+    // x is inf or nan.
+    if (LIBC_UNLIKELY(x_abs >= 0x7f80'0000U)) {
+      if (xbits.is_signaling_nan()) {
+        fputil::raise_except_if_required(FE_INVALID);
+        return FPBits::quiet_nan().get_val();
+      }
+
+      if (x_abs == 0x7f80'0000U) {
+        fputil::set_errno_if_required(EDOM);
+        fputil::raise_except_if_required(FE_INVALID);
+      }
+      return x + FPBits::quiet_nan().get_val();
+    }
+
+    return 1.0f;
+  }
+
+  // Combine the results with the sine of sum formula:
+  //   cos(pi * x) = cos((k + y)*pi/32)
+  //          = cos(y*pi/32) * cos(k*pi/32) - sin(y*pi/32) * sin(k*pi/32)
+  //          = (cosm1_y + 1) * cos_k - sin_y * sin_k
+  //          = (cosm1_y * cos_k + cos_k) - sin_y * sin_k
+  double sin_k = 0, cos_k = 0, sin_y = 0, cosm1_y = 0;
+
+  sincospif_eval(xd, sin_k, cos_k, sin_y, cosm1_y);
+
+  if (LIBC_UNLIKELY(sin_y == 0 && cos_k == 0)) {
+    return 0.0f;
+  }
+
+  return static_cast<float>(fputil::multiply_add(
+      sin_y, -sin_k, fputil::multiply_add(cosm1_y, cos_k, cos_k)));
+}
+
+} // namespace math
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC___SUPPORT_MATH_COSHF_H
diff --git a/libc/src/math/generic/CMakeLists.txt b/libc/src/math/generic/CMakeLists.txt
index 419f562713b5f..6c0dc1eeed692 100644
--- a/libc/src/math/generic/CMakeLists.txt
+++ b/libc/src/math/generic/CMakeLists.txt
@@ -315,12 +315,7 @@ add_entrypoint_object(
   HDRS
     ../cospif.h
   DEPENDS
-    libc.src.__support.math.sincosf_utils
-    libc.src.__support.FPUtil.fenv_impl
-    libc.src.__support.FPUtil.fp_bits
-    libc.src.__support.FPUtil.fma
-    libc.src.__support.FPUtil.multiply_add
-    libc.src.__support.macros.optimization
+    libc.src.__support.math.cospif
 )
 
 add_entrypoint_object(
diff --git a/libc/src/math/generic/cospif.cpp b/libc/src/math/generic/cospif.cpp
index 6b524a2cace7e..b9a4637da2ef4 100644
--- a/libc/src/math/generic/cospif.cpp
+++ b/libc/src/math/generic/cospif.cpp
@@ -7,95 +7,10 @@
 //===----------------------------------------------------------------------===//
 
 #include "src/math/cospif.h"
-#include "src/__support/FPUtil/FEnvImpl.h"
-#include "src/__support/FPUtil/FPBits.h"
-#include "src/__support/FPUtil/multiply_add.h"
-#include "src/__support/common.h"
-#include "src/__support/macros/config.h"
-#include "src/__support/macros/optimization.h"            // LIBC_UNLIKELY
-#include "src/__support/macros/properties/cpu_features.h" // LIBC_TARGET_CPU_HAS_FMA
-#include "src/__support/math/sincosf_utils.h"
+#include "src/__support/math/cospif.h"
 
 namespace LIBC_NAMESPACE_DECL {
 
-LLVM_LIBC_FUNCTION(float, cospif, (float x)) {
-  using FPBits = typename fputil::FPBits<float>;
-
-  FPBits xbits(x);
-  xbits.set_sign(Sign::POS);
-
-  uint32_t x_abs = xbits.uintval();
-  double xd = static_cast<double>(xbits.get_val());
-
-  // Range reduction:
-  // For |x| > 1/32, we perform range reduction as follows:
-  // Find k and y such that:
-  //   x = (k + y) * 1/32
-  //   k is an integer
-  //   |y| < 0.5
-  //
-  // This is done by performing:
-  //   k = round(x * 32)
-  //   y = x * 32 - k
-  //
-  // Once k and y are computed, we then deduce the answer by the cosine of sum
-  // formula:
-  //   cospi(x) = cos((k + y)*pi/32)
-  //          = cos(y*pi/32) * cos(k*pi/32) - sin(y*pi/32) * sin(k*pi/32)
-  // The values of sin(k*pi/32) and cos(k*pi/32) for k = 0..63 are precomputed
-  // and stored using a vector of 32 doubles. Sin(y*pi/32) and cos(y*pi/32) are
-  // computed using degree-7 and degree-6 minimax polynomials generated by
-  // Sollya respectively.
-
-  // The exhautive test passes for smaller values
-  if (LIBC_UNLIKELY(x_abs < 0x38A2'F984U)) {
-
-#if defined(LIBC_TARGET_CPU_HAS_FMA_FLOAT)
-    return fputil::multiply_add(xbits.get_val(), -0x1.0p-25f, 1.0f);
-#else
-    return static_cast<float>(fputil::multiply_add(xd, -0x1.0p-25, 1.0));
-#endif // LIBC_TARGET_CPU_HAS_FMA_FLOAT
-  }
-
-  // Numbers greater or equal to 2^23 are always integers or NaN
-  if (LIBC_UNLIKELY(x_abs >= 0x4B00'0000)) {
-
-    if (LIBC_UNLIKELY(x_abs < 0x4B80'0000)) {
-      return (x_abs & 0x1) ? -1.0f : 1.0f;
-    }
-
-    // x is inf or nan.
-    if (LIBC_UNLIKELY(x_abs >= 0x7f80'0000U)) {
-      if (xbits.is_signaling_nan()) {
-        fputil::raise_except_if_required(FE_INVALID);
-        return FPBits::quiet_nan().get_val();
-      }
-
-      if (x_abs == 0x7f80'0000U) {
-        fputil::set_errno_if_required(EDOM);
-        fputil::raise_except_if_required(FE_INVALID);
-      }
-      return x + FPBits::quiet_nan().get_val();
-    }
-
-    return 1.0f;
-  }
-
-  // Combine the results with the sine of sum formula:
-  //   cos(pi * x) = cos((k + y)*pi/32)
-  //          = cos(y*pi/32) * cos(k*pi/32) - sin(y*pi/32) * sin(k*pi/32)
-  //          = (cosm1_y + 1) * cos_k - sin_y * sin_k
-  //          = (cosm1_y * cos_k + cos_k) - sin_y * sin_k
-  double sin_k, cos_k, sin_y, cosm1_y;
-
-  sincospif_eval(xd, sin_k, cos_k, sin_y, cosm1_y);
-
-  if (LIBC_UNLIKELY(sin_y == 0 && cos_k == 0)) {
-    return 0.0f;
-  }
-
-  return static_cast<float>(fputil::multiply_add(
-      sin_y, -sin_k, fputil::multiply_add(cosm1_y, cos_k, cos_k)));
-}
+LLVM_LIBC_FUNCTION(float, cospif, (float x)) { return math::cospif(x); }
 
 } // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/test/shared/CMakeLists.txt b/libc/test/shared/CMakeLists.txt
index 3865fd8bcacc5..89d5b243b20a3 100644
--- a/libc/test/shared/CMakeLists.txt
+++ b/libc/test/shared/CMakeLists.txt
@@ -33,6 +33,7 @@ add_fp_unittest(
     libc.src.__support.math.cosf16
     libc.src.__support.math.coshf
     libc.src.__support.math.coshf16
+    libc.src.__support.math.cospif
     libc.src.__support.math.erff
     libc.src.__support.math.exp
     libc.src.__support.math.exp10
diff --git a/libc/test/shared/shared_math_test.cpp b/libc/test/shared/shared_math_test.cpp
index 048ff025cd1fb..c22543d3337ab 100644
--- a/libc/test/shared/shared_math_test.cpp
+++ b/libc/test/shared/shared_math_test.cpp
@@ -53,6 +53,7 @@ TEST(LlvmLibcSharedMathTest, AllFloat) {
   EXPECT_FP_EQ(0x0p+0f, LIBC_NAMESPACE::shared::cbrtf(0.0f));
   EXPECT_FP_EQ(0x1p+0f, LIBC_NAMESPACE::shared::cosf(0.0f));
   EXPECT_FP_EQ(0x1p+0f, LIBC_NAMESPACE::shared::coshf(0.0f));
+  EXPECT_FP_EQ(0x1p+0f, LIBC_NAMESPACE::shared::cospif(0.0f));
   EXPECT_FP_EQ(0x0p+0f, LIBC_NAMESPACE::shared::erff(0.0f));
   EXPECT_FP_EQ(0x1p+0f, LIBC_NAMESPACE::shared::exp10f(0.0f));
   EXPECT_FP_EQ(0x1p+0f, LIBC_NAMESPACE::shared::expf(0.0f));
diff --git a/utils/bazel/llvm-project-overlay/libc/BUILD.bazel b/utils/bazel/llvm-project-overlay/libc/BUILD.bazel
index 420f7d9c6e31c..88c4da323458a 100644
--- a/utils/bazel/llvm-project-overlay/libc/BUILD.bazel
+++ b/utils/bazel/llvm-project-overlay/libc/BUILD.bazel
@@ -2392,6 +2392,21 @@ libc_support_library(
     ],
 )
 
+libc_support_library(
+    name = "__support_math_cospif",
+    hdrs = ["src/__support/math/cospif.h"],
+    deps = [
+        ":__support_fputil_fma",
+        ":__support_fputil_multiply_add",
+        ":__support_fputil_nearest_integer",
+        ":__support_fputil_polyeval",
+        ":__support_fputil_rounding_mode",
+        ":__support_macros_optimization",
+        ":__support_sincosf_utils",
+        ":common_constants",
+    ],
+)
+
 libc_support_library(
     name = "__support_math_erff",
     hdrs = ["src/__support/math/erff.h"],
@@ -3220,14 +3235,7 @@ libc_math_function(
 libc_math_function(
     name = "cospif",
     additional_deps = [
-        ":__support_fputil_fma",
-        ":__support_fputil_multiply_add",
-        ":__support_fputil_nearest_integer",
-        ":__support_fputil_polyeval",
-        ":__support_fputil_rounding_mode",
-        ":__support_macros_optimization",
-        ":__support_sincosf_utils",
-        ":common_constants",
+        ":__support_math_cospif",
     ],
 )

bassiounix · 2025-08-22T01:42:18Z

Merge activity

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Aug 22, 1:45 AM UTC: Graphite rebased this pull request as part of a merge.
Aug 22, 1:53 AM UTC: @bassiounix merged this pull request with Graphite.

…upport/math folder.

bassiounix added bazel "Peripheral" support tier build system: utils/bazel libc labels Aug 18, 2025 — with Graphite App

bassiounix requested a review from lntue August 18, 2025 22:38

bassiounix marked this pull request as ready for review August 18, 2025 22:38

bassiounix requested review from rupprecht, keith and aaronmondal as code owners August 18, 2025 22:38

bassiounix removed request for keith, rupprecht and aaronmondal August 18, 2025 22:39

bassiounix mentioned this pull request Aug 18, 2025

[libc][math] Tracking Issue - Refactor Higher Math Functions to Header Only #147386

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bassiounix force-pushed the users/bassiounix/spr/08-19-_libc_math_refactor_cospif_implementation_to_header-only_in_src___support_math_folder branch from 94cbd2e to fb06fed Compare August 18, 2025 22:45

bassiounix mentioned this pull request Aug 18, 2025

[libc][math] Refactor cospif16 implementation to header-only in src/__support/math folder. #154222

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bassiounix force-pushed the users/bassiounix/spr/08-14-_libc_math_refactor_coshf16_implementation_to_header-only_in_src___support_math_folder branch from ef4490d to b320f74 Compare August 18, 2025 23:03

Base automatically changed from users/bassiounix/spr/08-14-_libc_math_refactor_coshf16_implementation_to_header-only_in_src___support_math_folder to main August 18, 2025 23:08

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bassiounix mentioned this pull request Aug 22, 2025

[libc][math] Refactor dsqrtl implementation to header-only in src/__support/math folder. #154868

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[libc][math] Refactor cospif implementation to header-only in src/__s…

bb73a0a

…upport/math folder.

bassiounix force-pushed the users/bassiounix/spr/08-19-_libc_math_refactor_cospif_implementation_to_header-only_in_src___support_math_folder branch from 0828e20 to bb73a0a Compare August 22, 2025 01:44

bassiounix merged commit 783859b into main Aug 22, 2025
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