Skip to content

[libc][math] Refactor exp2f implementation to header-only in src/__support/math folder. #161992

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Jump to bottom
Merged
merged 1 commit into from
Oct 6, 2025
Merged

[libc][math] Refactor exp2f implementation to header-only in src/__support/math folder. #161992

merged 1 commit into from
Oct 6, 2025
+80 −53

Conversation

bassiounix
Copy link
Contributor

@bassiounix bassiounix commented Oct 5, 2025 •
edited
Loading

This was referenced Oct 5, 2025
Merged
Merged
Merged
Merged
Merged
Merged
Merged
Merged
Merged
Merged
Merged
Merged
Merged
Merged
Merged
@bassiounix bassiounix requested a review from lntue October 5, 2025 03:11
This was referenced Oct 5, 2025
Merged
Merged
Merged
Merged
@bassiounix bassiounix added the bazel "Peripheral" support tier build system: utils/bazel label Oct 5, 2025 — with Graphite App
@bassiounix bassiounix mentioned this pull request Oct 5, 2025
Merged
@bassiounix bassiounix added the libc label Oct 5, 2025 — with Graphite App
This was referenced Oct 5, 2025
Merged
Merged
@bassiounix Graphite App
Copy link
Contributor Author

bassiounix commented Oct 5, 2025 •
edited
Loading

This stack of pull requests is managed by Graphite. Learn more about stacking.

@bassiounix bassiounix mentioned this pull request Oct 5, 2025
Merged
@bassiounix bassiounix marked this pull request as ready for review October 5, 2025 03:11
@bassiounix bassiounix requested review from rupprecht and keith October 5, 2025 03:11
@bassiounix bassiounix removed the request for review from rupprecht October 5, 2025 03:11
@llvmbot
Copy link
Member

llvmbot commented Oct 5, 2025

@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/161992.diff

10 Files Affected:

  • (modified) libc/shared/math.h (+1)
  • (added) libc/shared/math/exp2f.h (+23)
  • (modified) libc/src/__support/math/CMakeLists.txt (+18)
  • (renamed) libc/src/__support/math/exp2f.h (+12-10)
  • (modified) libc/src/math/generic/CMakeLists.txt (+2-20)
  • (modified) libc/src/math/generic/exp2f.cpp (+2-2)
  • (modified) libc/src/math/generic/powf.cpp (+2-3)
  • (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 (+18-18)
diff --git a/libc/shared/math.h b/libc/shared/math.h
index 924d0cb4f3bfa..1262fa6f682d0 100644
--- a/libc/shared/math.h
+++ b/libc/shared/math.h
@@ -48,6 +48,7 @@
 #include "math/exp10m1f.h"
 #include "math/exp10m1f16.h"
 #include "math/exp2.h"
+#include "math/exp2f.h"
 #include "math/expf.h"
 #include "math/expf16.h"
 #include "math/frexpf.h"
diff --git a/libc/shared/math/exp2f.h b/libc/shared/math/exp2f.h
new file mode 100644
index 0000000000000..8c37cbb702e91
--- /dev/null
+++ b/libc/shared/math/exp2f.h
@@ -0,0 +1,23 @@
+//===-- Shared exp2f 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_EXP2F_H
+#define LLVM_LIBC_SHARED_MATH_EXP2F_H
+
+#include "shared/libc_common.h"
+#include "src/__support/math/exp2f.h"
+
+namespace LIBC_NAMESPACE_DECL {
+namespace shared {
+
+using math::exp2f;
+
+} // namespace shared
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SHARED_MATH_EXP2F_H
diff --git a/libc/src/__support/math/CMakeLists.txt b/libc/src/__support/math/CMakeLists.txt
index 4130fdf02078b..1d49eaecea23b 100644
--- a/libc/src/__support/math/CMakeLists.txt
+++ b/libc/src/__support/math/CMakeLists.txt
@@ -735,6 +735,24 @@ add_header_library(
     libc.src.errno.errno
 )
 
+add_header_library(
+  exp2f
+  HDRS
+    exp2f.h
+  DEPENDS
+    libc.src.__support.FPUtil.except_value_utils
+    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.macros.optimization
+    libc.src.__support.math.exp10f_utils
+    libc.src.__support.common
+    libc.src.errno.errno
+)
+
 add_header_library(
   exp10
   HDRS
diff --git a/libc/src/math/generic/exp2f_impl.h b/libc/src/__support/math/exp2f.h
similarity index 94%
rename from libc/src/math/generic/exp2f_impl.h
rename to libc/src/__support/math/exp2f.h
index b85bb1548019f..ef2aad051b8a9 100644
--- a/libc/src/math/generic/exp2f_impl.h
+++ b/libc/src/__support/math/exp2f.h
@@ -1,4 +1,4 @@
-//===-- Single-precision 2^x function -------------------------------------===//
+//===-- Implementation header for exp2f -------------------------*- C++ -*-===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
@@ -6,9 +6,10 @@
 //
 //===----------------------------------------------------------------------===//
 
-#ifndef LLVM_LIBC_SRC_MATH_GENERIC_EXP2F_IMPL_H
-#define LLVM_LIBC_SRC_MATH_GENERIC_EXP2F_IMPL_H
+#ifndef LLVM_LIBC_SRC___SUPPORT_MATH_EXP2F_H
+#define LLVM_LIBC_SRC___SUPPORT_MATH_EXP2F_H
 
+#include "exp10f_utils.h"
 #include "src/__support/FPUtil/FEnvImpl.h"
 #include "src/__support/FPUtil/FPBits.h"
 #include "src/__support/FPUtil/PolyEval.h"
@@ -20,12 +21,12 @@
 #include "src/__support/macros/config.h"
 #include "src/__support/macros/optimization.h" // LIBC_UNLIKELY
 #include "src/__support/macros/properties/cpu_features.h"
-#include "src/__support/math/exp10f_utils.h"
 
 namespace LIBC_NAMESPACE_DECL {
-namespace generic {
 
-LIBC_INLINE float exp2f(float x) {
+namespace math {
+
+LIBC_INLINE static constexpr float exp2f(float x) {
   using FPBits = typename fputil::FPBits<float>;
   FPBits xbits(x);
 
@@ -120,8 +121,8 @@ LIBC_INLINE float exp2f(float x) {
   // of 2^mid.
 
   // kf = (hi + mid) * 2^5 = round(x * 2^5)
-  float kf;
-  int k;
+  float kf = 0;
+  int k = 0;
 #ifdef LIBC_TARGET_CPU_HAS_NEAREST_INT
   kf = fputil::nearest_integer(x * 32.0f);
   k = static_cast<int>(kf);
@@ -161,7 +162,8 @@ LIBC_INLINE float exp2f(float x) {
   return static_cast<float>(fputil::multiply_add(p, dx_sq * mh, c1 * mh));
 }
 
-} // namespace generic
+} // namespace math
+
 } // namespace LIBC_NAMESPACE_DECL
 
-#endif // LLVM_LIBC_SRC_MATH_GENERIC_EXP2F_IMPL_H
+#endif // LLVM_LIBC_SRC___SUPPORT_MATH_EXP2F_H
diff --git a/libc/src/math/generic/CMakeLists.txt b/libc/src/math/generic/CMakeLists.txt
index 28ea475f09656..5738fe86f6c7b 100644
--- a/libc/src/math/generic/CMakeLists.txt
+++ b/libc/src/math/generic/CMakeLists.txt
@@ -1451,24 +1451,6 @@ add_entrypoint_object(
     libc.src.__support.math.exp2
 )
 
-add_header_library(
-  exp2f_impl
-  HDRS
-    exp2f_impl.h
-  DEPENDS
-    libc.src.__support.FPUtil.except_value_utils
-    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.macros.optimization
-    libc.src.__support.math.exp10f_utils
-    libc.src.__support.common
-    libc.src.errno.errno
-)
-
 add_entrypoint_object(
   exp2f
   SRCS
@@ -1476,7 +1458,7 @@ add_entrypoint_object(
   HDRS
     ../exp2f.h
   DEPENDS
-    .exp2f_impl
+    libc.src.__support.math.exp2f
 )
 
 add_entrypoint_object(
@@ -1659,8 +1641,8 @@ add_entrypoint_object(
   HDRS
     ../powf.h
   DEPENDS
-    .exp2f_impl
     libc.src.__support.math.exp10f
+    libc.src.__support.math.exp2f
     libc.src.__support.CPP.bit
     libc.src.__support.FPUtil.fenv_impl
     libc.src.__support.FPUtil.fp_bits
diff --git a/libc/src/math/generic/exp2f.cpp b/libc/src/math/generic/exp2f.cpp
index 60d6510f23699..3117f73b59bcf 100644
--- a/libc/src/math/generic/exp2f.cpp
+++ b/libc/src/math/generic/exp2f.cpp
@@ -9,10 +9,10 @@
 #include "src/math/exp2f.h"
 #include "src/__support/common.h" // for LLVM_LIBC_FUNCTION
 #include "src/__support/macros/config.h"
-#include "src/math/generic/exp2f_impl.h"
+#include "src/__support/math/exp2f.h"
 
 namespace LIBC_NAMESPACE_DECL {
 
-LLVM_LIBC_FUNCTION(float, exp2f, (float x)) { return generic::exp2f(x); }
+LLVM_LIBC_FUNCTION(float, exp2f, (float x)) { return math::exp2f(x); }
 
 } // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/math/generic/powf.cpp b/libc/src/math/generic/powf.cpp
index 12246e9878758..dd2b6aa788b9b 100644
--- a/libc/src/math/generic/powf.cpp
+++ b/libc/src/math/generic/powf.cpp
@@ -20,10 +20,9 @@
 #include "src/__support/macros/optimization.h" // LIBC_UNLIKELY
 #include "src/__support/math/common_constants.h" // Lookup tables EXP_M1 and EXP_M2.
 #include "src/__support/math/exp10f.h" // Speedup for powf(10, y) = exp10f(y)
+#include "src/__support/math/exp2f.h"  // Speedup for powf(2, y) = exp2f(y)
 #include "src/__support/math/exp_constants.h"
 
-#include "exp2f_impl.h"  // Speedup for powf(2, y) = exp2f(y)
-
 namespace LIBC_NAMESPACE_DECL {
 
 using fputil::DoubleDouble;
@@ -779,7 +778,7 @@ LLVM_LIBC_FUNCTION(float, powf, (float x, float y)) {
 #ifndef LIBC_MATH_HAS_SKIP_ACCURATE_PASS
     case 0x4000'0000: // x = 2.0f
       // pow(2, y) = exp2(y)
-      return generic::exp2f(y);
+      return math::exp2f(y);
     case 0x4120'0000: // x = 10.0f
       // pow(10, y) = exp10(y)
       return math::exp10f(y);
diff --git a/libc/test/shared/CMakeLists.txt b/libc/test/shared/CMakeLists.txt
index 040f6356b2577..dbc3889c76471 100644
--- a/libc/test/shared/CMakeLists.txt
+++ b/libc/test/shared/CMakeLists.txt
@@ -41,6 +41,7 @@ add_fp_unittest(
     libc.src.__support.math.erff
     libc.src.__support.math.exp
     libc.src.__support.math.exp2
+    libc.src.__support.math.exp2f
     libc.src.__support.math.exp10
     libc.src.__support.math.exp10f
     libc.src.__support.math.exp10f16
diff --git a/libc/test/shared/shared_math_test.cpp b/libc/test/shared/shared_math_test.cpp
index ef2e7b8d71456..d118d96da69dd 100644
--- a/libc/test/shared/shared_math_test.cpp
+++ b/libc/test/shared/shared_math_test.cpp
@@ -62,6 +62,7 @@ TEST(LlvmLibcSharedMathTest, AllFloat) {
   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));
+  EXPECT_FP_EQ(0x1p+0f, LIBC_NAMESPACE::shared::exp2f(0.0f));
 
   EXPECT_FP_EQ_ALL_ROUNDING(0.75f,
                             LIBC_NAMESPACE::shared::frexpf(24.0f, &exponent));
diff --git a/utils/bazel/llvm-project-overlay/libc/BUILD.bazel b/utils/bazel/llvm-project-overlay/libc/BUILD.bazel
index e91e7c8aa7c86..00db514beaf34 100644
--- a/utils/bazel/llvm-project-overlay/libc/BUILD.bazel
+++ b/utils/bazel/llvm-project-overlay/libc/BUILD.bazel
@@ -2167,22 +2167,6 @@ libc_support_library(
     ],
 )
 
-libc_support_library(
-    name = "exp2f_impl",
-    hdrs = ["src/math/generic/exp2f_impl.h"],
-    deps = [
-        ":__support_fputil_except_value_utils",
-        ":__support_fputil_fma",
-        ":__support_fputil_multiply_add",
-        ":__support_fputil_nearest_integer",
-        ":__support_fputil_polyeval",
-        ":__support_fputil_rounding_mode",
-        ":__support_macros_optimization",
-        ":__support_math_common_constants",
-        ":__support_math_exp10f_utils",
-    ],
-)
-
 libc_support_library(
     name = "__support_math_acos",
     hdrs = ["src/__support/math/acos.h"],
@@ -2895,6 +2879,22 @@ libc_support_library(
     ],
 )
 
+libc_support_library(
+    name = "__support_math_exp2f",
+    hdrs = ["src/__support/math/exp2f.h"],
+    deps = [
+        ":__support_fputil_except_value_utils",
+        ":__support_fputil_fma",
+        ":__support_fputil_multiply_add",
+        ":__support_fputil_nearest_integer",
+        ":__support_fputil_polyeval",
+        ":__support_fputil_rounding_mode",
+        ":__support_macros_optimization",
+        ":__support_math_common_constants",
+        ":__support_math_exp10f_utils",
+    ],
+)
+
 libc_support_library(
     name = "__support_math_exp10",
     hdrs = ["src/__support/math/exp10.h"],
@@ -3676,7 +3676,7 @@ libc_math_function(
 libc_math_function(
     name = "exp2f",
     additional_deps = [
-        ":exp2f_impl",
+        ":__support_math_exp2f",
     ],
 )
 
@@ -4511,7 +4511,7 @@ libc_math_function(
         ":__support_macros_optimization",
         ":__support_math_exp10f",
         ":__support_math_common_constants",
-        ":exp2f_impl",
+        ":__support_math_exp2f",
     ],
 )

@bassiounix bassiounix mentioned this pull request Oct 5, 2025
Open
@bassiounix bassiounix force-pushed the users/bassiounix/spr/09-30-_libc_math_refactor_exp2_implementation_to_header-only_in_src___support_math_folder branch from d06e697 to d2bbd3b Compare October 5, 2025 03:25
Base automatically changed from users/bassiounix/spr/09-30-_libc_math_refactor_exp2_implementation_to_header-only_in_src___support_math_folder to main October 5, 2025 03:31
@bassiounix bassiounix force-pushed the users/bassiounix/spr/10-05-_libc_math_refactor_exp2f_implementation_to_header-only_in_src___support_math_folder branch 2 times, most recently from febce61 to db744db Compare October 5, 2025 03:47
This was referenced Oct 5, 2025
Open
Open
Open
@bassiounix Graphite App
Copy link
Contributor Author

bassiounix commented Oct 6, 2025 •
edited
Loading

Merge activity

  • Oct 6, 5:17 PM UTC: A user started a stack merge that includes this pull request via Graphite.
  • Oct 6, 5:20 PM UTC: Graphite rebased this pull request as part of a merge.
  • Oct 6, 5:24 PM UTC: Graphite rebased this pull request as part of a merge.
  • Oct 6, 5:33 PM UTC: Graphite rebased this pull request as part of a merge.
  • Oct 6, 5:35 PM UTC: Graphite rebased this pull request as part of a merge.
  • Oct 6, 5:41 PM UTC: Graphite rebased this pull request as part of a merge.
  • Oct 6, 5:42 PM UTC: Graphite rebased this pull request as part of a merge.
  • Oct 6, 5:52 PM UTC: Graphite rebased this pull request as part of a merge.
  • Oct 6, 6:00 PM UTC: Graphite rebased this pull request as part of a merge.
  • Oct 6, 6:06 PM UTC: Graphite rebased this pull request as part of a merge.
  • Oct 6, 6:17 PM UTC: Graphite rebased this pull request as part of a merge.
  • Oct 6, 6:23 PM UTC: @bassiounix merged this pull request with Graphite.

@bassiounix bassiounix force-pushed the users/bassiounix/spr/10-05-_libc_math_refactor_exp2f_implementation_to_header-only_in_src___support_math_folder branch 7 times, most recently from fbb9605 to 93383ba Compare October 6, 2025 17:42
@bassiounix bassiounix mentioned this pull request Oct 6, 2025
Open
@bassiounix bassiounix force-pushed the users/bassiounix/spr/10-05-_libc_math_refactor_exp2f_implementation_to_header-only_in_src___support_math_folder branch 3 times, most recently from a6a49dd to 4c05856 Compare October 6, 2025 18:03
@bassiounix bassiounix mentioned this pull request Oct 6, 2025
Open
@bassiounix bassiounix force-pushed the users/bassiounix/spr/10-05-_libc_math_refactor_exp2f_implementation_to_header-only_in_src___support_math_folder branch from 4c05856 to 49a99a9 Compare October 6, 2025 18:05
@bassiounix bassiounix force-pushed the users/bassiounix/spr/10-05-_libc_math_refactor_exp2f_implementation_to_header-only_in_src___support_math_folder branch from 49a99a9 to 20f4f60 Compare October 6, 2025 18:16
@bassiounix bassiounix merged commit 596ff85 into main Oct 6, 2025
20 checks passed
@bassiounix bassiounix deleted the users/bassiounix/spr/10-05-_libc_math_refactor_exp2f_implementation_to_header-only_in_src___support_math_folder branch October 6, 2025 18:23
@bassiounix bassiounix mentioned this pull request Oct 6, 2025
Open
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
Reviewers

@lntue lntue lntue approved these changes

Assignees
No one assigned
Labels
bazel "Peripheral" support tier build system: utils/bazel libc
Projects
None yet
Milestone
No milestone
Development

Successfully merging this pull request may close these issues.
3 participants
@bassiounix @llvmbot @lntue