[libc-commits] [libc] [llvm] [libc][math] Improve atanf performance. (PR #85463)

via libc-commits libc-commits at lists.llvm.org
Fri Mar 15 14:44:17 PDT 2024


https://github.com/lntue updated https://github.com/llvm/llvm-project/pull/85463

>From 2e5993fc5ad61b81c3680bfed551f08824d77d73 Mon Sep 17 00:00:00 2001
From: Tue Ly <lntue at google.com>
Date: Fri, 15 Mar 2024 15:51:47 -0400
Subject: [PATCH 1/2] [libc][math] Improve atanf performance.

---
 libc/src/math/generic/CMakeLists.txt          |  31 +++--
 libc/src/math/generic/atanf.cpp               | 120 +++++++++++++-----
 libc/src/math/generic/inv_trigf_utils.cpp     |  80 ++++++++++--
 libc/src/math/generic/inv_trigf_utils.h       |  83 +++---------
 libc/test/src/math/exhaustive/atanf_test.cpp  |   2 +-
 .../llvm-project-overlay/libc/BUILD.bazel     |   4 -
 6 files changed, 188 insertions(+), 132 deletions(-)

diff --git a/libc/src/math/generic/CMakeLists.txt b/libc/src/math/generic/CMakeLists.txt
index 87f53105a1b317..a8f3f6be36022a 100644
--- a/libc/src/math/generic/CMakeLists.txt
+++ b/libc/src/math/generic/CMakeLists.txt
@@ -2057,16 +2057,9 @@ add_object_library(
   SRCS
     inv_trigf_utils.cpp
   DEPENDS
-    .math_utils
-    libc.src.__support.FPUtil.fp_bits
-    libc.src.__support.FPUtil.fenv_impl
-    libc.src.__support.FPUtil.nearest_integer
-    libc.src.__support.FPUtil.nearest_integer_operations
+    libc.src.__support.FPUtil.multiply_add
     libc.src.__support.FPUtil.polyeval
     libc.src.__support.common
-    libc.include.errno
-    libc.src.errno.errno
-    libc.include.math
 )
 
 add_entrypoint_object(
@@ -2112,15 +2105,33 @@ add_entrypoint_object(
   HDRS
     ../atanf.h
   DEPENDS
-    .inv_trigf_utils
-    .math_utils
+    libc.src.__support.FPUtil.except_value_utils
     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
   COMPILE_OPTIONS
     -O3
 )
 
+add_entrypoint_object(
+  atan2f
+  SRCS
+    atan2f.cpp
+  HDRS
+    ../atan2f.h
+  COMPILE_OPTIONS
+    -O3
+  DEPENDS
+    .inv_trigf_utils
+    .math_utils
+    libc.src.__support.FPUtil.fp_bits
+    libc.src.__support.FPUtil.rounding_mode
+    libc.src.__support.macros.optimization
+)
+
 add_entrypoint_object(
   scalbn
   SRCS
diff --git a/libc/src/math/generic/atanf.cpp b/libc/src/math/generic/atanf.cpp
index e0f8a1bfc2ecc9..2ed5135c669348 100644
--- a/libc/src/math/generic/atanf.cpp
+++ b/libc/src/math/generic/atanf.cpp
@@ -7,11 +7,14 @@
 //===----------------------------------------------------------------------===//
 
 #include "src/math/atanf.h"
-#include "math_utils.h"
 #include "src/__support/FPUtil/FPBits.h"
+#include "src/__support/FPUtil/PolyEval.h"
+#include "src/__support/FPUtil/except_value_utils.h"
+#include "src/__support/FPUtil/multiply_add.h"
+#include "src/__support/FPUtil/nearest_integer.h"
 #include "src/__support/FPUtil/rounding_mode.h"
 #include "src/__support/macros/optimization.h" // LIBC_UNLIKELY
-#include "src/math/generic/inv_trigf_utils.h"
+#include "inv_trigf_utils.h"
 
 namespace LIBC_NAMESPACE {
 
@@ -19,48 +22,95 @@ LLVM_LIBC_FUNCTION(float, atanf, (float x)) {
   using FPBits = typename fputil::FPBits<float>;
   using Sign = fputil::Sign;
 
-  // x == 0.0
-  if (LIBC_UNLIKELY(x == 0.0f))
-    return x;
+  constexpr double FINAL_SIGN[2] = {1.0, -1.0};
+  constexpr double SIGNED_PI_OVER_2[2] = {0x1.921fb54442d18p0,
+                                          -0x1.921fb54442d18p0};
 
-  FPBits xbits(x);
-  Sign sign = xbits.sign();
-  xbits.set_sign(Sign::POS);
+  FPBits x_bits(x);
+  Sign sign = x_bits.sign();
+  x_bits.set_sign(Sign::POS);
+  uint32_t x_abs = x_bits.uintval();
 
-  if (LIBC_UNLIKELY(xbits.is_inf_or_nan())) {
-    if (xbits.is_inf())
-      return static_cast<float>(
-          opt_barrier(sign.is_neg() ? -M_MATH_PI_2 : M_MATH_PI_2));
-    else
+  // x is inf or nan, |x| < 2^-4 or |x|= > 16.
+  if (LIBC_UNLIKELY(x_abs <= 0x3d80'0000U || x_abs >= 0x4180'0000U)) {
+    double x_d = static_cast<double>(x);
+    double const_term = 0.0;
+    if (LIBC_UNLIKELY(x_abs >= 0x4180'0000)) {
+      // atan(+-Inf) = +-pi/2.
+      if (x_bits.is_inf())
+        return static_cast<float>(SIGNED_PI_OVER_2[sign.is_neg()]);
+      if (x_bits.is_nan())
+        return x;
+      // x >= 16
+      x_d = -1.0 / x_d;
+      const_term = SIGNED_PI_OVER_2[sign.is_neg()];
+    }
+    // 0 <= x < 1/16;
+    if (LIBC_UNLIKELY(x_bits.is_zero()))
       return x;
-  }
-  // |x| == 0.06905200332403183
-  if (LIBC_UNLIKELY(xbits.uintval() == 0x3d8d6b23U)) {
-    if (fputil::fenv_is_round_to_nearest()) {
-      // 0.06894256919622421
-      FPBits br(0x3d8d31c3U);
-      br.set_sign(sign);
-      return br.get_val();
+    // x <= 2^-12;
+    if (LIBC_UNLIKELY(x_abs < 0x3980'0000)) {
+#if defined(LIBC_TARGET_CPU_HAS_FMA)
+      return fputil::multiply_add(x, -0x1.0p-25f, x);
+#else
+      double x_d = static_cast<double>(x);
+      return static_cast<float>(fputil::multiply_add(x_d, -0x1.0p-25, x_d));
+#endif // LIBC_TARGET_CPU_HAS_FMA
     }
+    // Use Taylor polynomial:
+    //   atan(x) ~ x * (1 - x^2 / 3 + x^4 / 5 - x^6 / 7 + x^8 / 9 - x^10 / 11).
+    double x2 = x_d * x_d;
+    double x4 = x2 * x2;
+    double c0 = fputil::multiply_add(x2, ATAN_COEFFS[0][1], ATAN_COEFFS[0][0]);
+    double c1 = fputil::multiply_add(x2, ATAN_COEFFS[0][3], ATAN_COEFFS[0][2]);
+    double c2 = fputil::multiply_add(x2, ATAN_COEFFS[0][5], ATAN_COEFFS[0][4]);
+    double p = fputil::polyeval(x4, c0, c1, c2);
+    double r = fputil::multiply_add(x_d, p, const_term);
+    return static_cast<float>(r);
   }
 
-  // |x| == 1.8670953512191772
-  if (LIBC_UNLIKELY(xbits.uintval() == 0x3feefcfbU)) {
-    int rounding_mode = fputil::quick_get_round();
-    if (sign.is_neg()) {
-      if (rounding_mode == FE_DOWNWARD) {
-        // -1.0790828466415405
-        return FPBits(0xbf8a1f63U).get_val();
-      }
-    } else {
-      if (rounding_mode == FE_UPWARD) {
-        // 1.0790828466415405
-        return FPBits(0x3f8a1f63U).get_val();
-      }
+  // Range reduction steps:
+  // 1)  atan(x) = sign(x) * atan(|x|)
+  // 2)  If |x| > 1, atan(|x|) = pi/2 - atan(1/|x|)
+  // 3)  For 1/16 < x <= 1, we find k such that: |x - k/16| <= 1/32.
+  // 4)  Then we use polynomial approximation:
+  //   atan(x) ~ atan((k/16) + (x - (k/16)) * Q(x - k/16)
+  //           = P(x - k/16)
+  double x_d, const_term, final_sign;
+  int idx;
+
+  if (x_abs > 0x3f80'0000U) {
+    // |x| > 1, we need to invert x, so we will perform range reduction in
+    // double precision.
+    x_d = 1.0 / static_cast<double>(x_bits.get_val());
+    double k_d = fputil::nearest_integer(x_d * 0x1.0p4);
+    x_d = fputil::multiply_add(k_d, -0x1.0p-4, x_d);
+    idx = static_cast<int>(k_d);
+    final_sign = FINAL_SIGN[sign.is_pos()];
+    // Adjust constant term of the polynomial by +- pi/2.
+    const_term = fputil::multiply_add(final_sign, ATAN_COEFFS[idx][0],
+                                      SIGNED_PI_OVER_2[sign.is_neg()]);
+  } else {
+    // Exceptional value:
+    if (LIBC_UNLIKELY(x_abs == 0x3dbb'6ac7U)) {
+      return sign.is_pos()
+                 ? fputil::round_result_slightly_up(0x1.75cb06p-4f)
+                 : fputil::round_result_slightly_down(-0x1.75cb06p-4f);
     }
+    // Perform range reduction in single precision.
+    float x_f = x_bits.get_val();
+    float k_f = fputil::nearest_integer(x_f * 0x1.0p4f);
+    x_f = fputil::multiply_add(k_f, -0x1.0p-4f, x_f);
+    x_d = static_cast<double>(x_f);
+    idx = static_cast<int>(k_f);
+    final_sign = FINAL_SIGN[sign.is_neg()];
+    const_term = final_sign * ATAN_COEFFS[idx][0];
   }
 
-  return static_cast<float>(atan_eval(x));
+  double p = atan_eval(x_d, idx);
+  double r = fputil::multiply_add(final_sign * x_d, p, const_term);
+
+  return static_cast<float>(r);
 }
 
 } // namespace LIBC_NAMESPACE
diff --git a/libc/src/math/generic/inv_trigf_utils.cpp b/libc/src/math/generic/inv_trigf_utils.cpp
index 8013c0470affb1..93d5bcbf7b567d 100644
--- a/libc/src/math/generic/inv_trigf_utils.cpp
+++ b/libc/src/math/generic/inv_trigf_utils.cpp
@@ -10,19 +10,71 @@
 
 namespace LIBC_NAMESPACE {
 
-// N[Table[ArcTan[x], {x, 1/16, 16/16, 1/16}], 40]
-alignas(64) const double ATAN_T[ATAN_T_SIZE] = {
-    0x1.ff55bb72cfdeap-5, 0x1.fd5ba9aac2f6ep-4, 0x1.7b97b4bce5b02p-3,
-    0x1.f5b75f92c80ddp-3, 0x1.362773707ebccp-2, 0x1.6f61941e4def1p-2,
-    0x1.a64eec3cc23fdp-2, 0x1.dac670561bb4fp-2, 0x1.0657e94db30d0p-1,
-    0x1.1e00babdefeb4p-1, 0x1.345f01cce37bbp-1, 0x1.4978fa3269ee1p-1,
-    0x1.5d58987169b18p-1, 0x1.700a7c5784634p-1, 0x1.819d0b7158a4dp-1,
-    0x1.921fb54442d18p-1};
-
-// for(int i = 0; i < 5; i++)
-//     printf("%.13a,\n", (-2 * (i % 2) + 1) * 1.0 / (2 * i + 1));
-alignas(64) const double ATAN_K[5] = {
-    0x1.0000000000000p+0, -0x1.5555555555555p-2, 0x1.999999999999ap-3,
-    -0x1.2492492492492p-3, 0x1.c71c71c71c71cp-4};
+// Polynomial approximation for 0 <= x <= 1:
+//   atan(x) ~ atan((i/16) + (x - (i/16)) * Q(x - i/16)
+//           = P(x - i/16)
+// Generated by Sollya with:
+// > for i from 1 to 16 do {
+//     mid_point = i/16;
+//     P = fpminimax(atan(mid_point + x), 7, [|D...|], [-1/32, 1/32]);
+//     print("{", coeff(P, 0), ",", coeff(P, 1), ",", coeff(P, 2), ",",
+//           coeff(P, 3), ",", coeff(P, 4), ",", coeff(P, 5), ",", coeff(P, 6),
+//           ",", coeff(P, 7), "},");
+//   };
+// For i = 0, ATAN_COEFFS[0][j] = (-1)^j * (1/(2*j + 1)) is the odd coefficients
+// of the Taylor polynomial of atan(x).
+double ATAN_COEFFS[17][8] = {
+    {0x1.0000000000000p+0, -0x1.5555555555555p-2, 0x1.999999999999ap-3,
+     -0x1.2492492492492p-3, 0x1.c71c71c71c71cp-4, -0x1.745d1745d1746p-4,
+     0x1.3b13b13b13b14p-4, -0x1.1111111111111p-4},
+    {0x1.ff55bb72cfdb1p-5, 0x1.fe01fe01fe1bp-1, -0x1.fc05f80821d1ap-5,
+     -0x1.4d6930419fc5fp-2, 0x1.f61b9f6d69313p-5, 0x1.8208a32f4346cp-3,
+     -0x1.ecb8fc53d04efp-5, -0x1.060710cb59cbcp-3},
+    {0x1.fd5ba9aac2f3cp-4, 0x1.f81f81f81f96ap-1, -0x1.f05e09cf4c1b2p-4,
+     -0x1.368c3aac7543ep-2, 0x1.d9b14bddfac55p-4, 0x1.4048e55ec725ep-3,
+     -0x1.b98ca3c1594b5p-4, -0x1.664eabaabbc16p-4},
+    {0x1.7b97b4bce5ae7p-3, 0x1.ee9c7f8458f06p-1, -0x1.665c226c8dc69p-3,
+     -0x1.1344bb77961b7p-2, 0x1.42ac97745d3ccp-3, 0x1.c32e142047ec1p-4,
+     -0x1.137ae41ab96cbp-3, -0x1.1a6ae8c09a4b6p-5},
+    {0x1.f5b75f92c80c6p-3, 0x1.e1e1e1e1e1ed4p-1, -0x1.c5894d101ad4p-3,
+     -0x1.ce6de02b38c38p-3, 0x1.78a3920c336b9p-3, 0x1.dd5ff94a9d499p-5,
+     -0x1.1ac2d3f9d072ep-3, 0x1.0af9735dff373p-6},
+    {0x1.362773707ebc5p-2, 0x1.d272ca3fc5b8bp-1, -0x1.0997e8ae90cb6p-2,
+     -0x1.6cf6667146798p-3, 0x1.8dd1dff17f3d3p-3, 0x1.24860eced656fp-7,
+     -0x1.f4220e8f18ed5p-4, 0x1.b700aed7cdc34p-5},
+    {0x1.6f61941e4deeep-2, 0x1.c0e070381c115p-1, -0x1.2726dd1347c7ep-2,
+     -0x1.09f37b3ad010dp-3, 0x1.85eaca5196f5cp-3, -0x1.04d640117852ap-5,
+     -0x1.802c2956871c7p-4, 0x1.2992b45df0ee7p-4},
+    {0x1.a64eec3cc23fep-2, 0x1.adbe87f94906bp-1, -0x1.3b9d8eab5eae5p-2,
+     -0x1.57c09646faabbp-4, 0x1.6795330e73aep-3, -0x1.f2d89a702a652p-5,
+     -0x1.f3afd90a9d4d7p-5, 0x1.3261723d3f153p-4},
+    {0x1.dac670561bb53p-2, 0x1.999999999998fp-1, -0x1.47ae147afd8cap-2,
+     -0x1.5d867c3dfd72ap-5, 0x1.3a92a76cba833p-3, -0x1.3ec460286928ap-4,
+     -0x1.ed02ff86892acp-6, 0x1.0a674c8f05727p-4},
+    {0x1.0657e94db30d2p-1, 0x1.84f00c27805ffp-1, -0x1.4c62cb564f677p-2,
+     -0x1.e6495b262dfe7p-8, 0x1.063c34eca262bp-3, -0x1.58b78dc79b5aep-4,
+     -0x1.4623815233be1p-8, 0x1.93afe94328089p-5},
+    {0x1.1e00babdefeb6p-1, 0x1.702e05c0b8159p-1, -0x1.4af2b78236bd6p-2,
+     0x1.5d0b7ea46ed08p-6, 0x1.a124870236935p-4, -0x1.519e1ec133a88p-4,
+     0x1.a54632a3f48c7p-7, 0x1.099ca0945096dp-5},
+    {0x1.345f01cce37bdp-1, 0x1.5babcc647fa7ep-1, -0x1.449db09443a67p-2,
+     0x1.655caac78a0fcp-5, 0x1.3bbbdb0d09efap-4, -0x1.34a306c27e021p-4,
+     0x1.83fe749c7966p-6, 0x1.2057cc96d9edcp-6},
+    {0x1.4978fa3269ee2p-1, 0x1.47ae147ae146bp-1, -0x1.3a92a305652e1p-2,
+     0x1.ec21b5172657fp-5, 0x1.c2f8c45d2f4eep-5, -0x1.0ba99c4aeb8acp-4,
+     0x1.d716a4af4d1d6p-6, 0x1.97fba0a9696dep-8},
+    {0x1.5d58987169b19p-1, 0x1.34679ace0133cp-1, -0x1.2ddfb03920e2fp-2,
+     0x1.2491307c0fa0bp-4, 0x1.29c7eca0136fp-5, -0x1.bca792caa6f1cp-5,
+     0x1.e5d92545576bcp-6, -0x1.8ca76fcf5ccd2p-10},
+    {0x1.700a7c5784634p-1, 0x1.21fb78121fb71p-1, -0x1.1f6a8499ea541p-2,
+     0x1.41b15e5e77bcfp-4, 0x1.59bc9bf54fb02p-6, -0x1.63b54ff058e0fp-5,
+     0x1.c8da01221306fp-6, -0x1.906b2c274c39cp-8},
+    {0x1.819d0b7158a4dp-1, 0x1.107fbbe01107cp-1, -0x1.0feeb40897d4ep-2,
+     0x1.50e5afb95f5d6p-4, 0x1.2a7c2f0c7495dp-7, -0x1.12bd2bb5062cdp-5,
+     0x1.93e8ceb89afebp-6, -0x1.10da9b8c6b731p-7},
+    {0x1.921fb54442d18p-1, 0x1.fffffffffffebp-2, -0x1.fffffffffcbbcp-3,
+     0x1.555555564e2fep-4, -0x1.20b17d5dd89dcp-30, -0x1.9999c5ad71711p-6,
+     0x1.5558b76e7aaf9p-6, -0x1.236e803c6c1f6p-7},
+};
 
 } // namespace LIBC_NAMESPACE
diff --git a/libc/src/math/generic/inv_trigf_utils.h b/libc/src/math/generic/inv_trigf_utils.h
index 20f912de2ac008..308bdc44e3f8ac 100644
--- a/libc/src/math/generic/inv_trigf_utils.h
+++ b/libc/src/math/generic/inv_trigf_utils.h
@@ -9,85 +9,32 @@
 #ifndef LLVM_LIBC_SRC_MATH_GENERIC_INV_TRIGF_UTILS_H
 #define LLVM_LIBC_SRC_MATH_GENERIC_INV_TRIGF_UTILS_H
 
-#include "math_utils.h"
-#include "src/__support/FPUtil/FEnvImpl.h"
-#include "src/__support/FPUtil/FPBits.h"
 #include "src/__support/FPUtil/PolyEval.h"
-#include "src/__support/FPUtil/nearest_integer.h"
+#include "src/__support/FPUtil/multiply_add.h"
 #include "src/__support/common.h"
 
-#include <errno.h>
-
 namespace LIBC_NAMESPACE {
 
 // PI and PI / 2
 constexpr double M_MATH_PI = 0x1.921fb54442d18p+1;
 constexpr double M_MATH_PI_2 = 0x1.921fb54442d18p+0;
 
-// atan table size
-constexpr int ATAN_T_BITS = 4;
-constexpr int ATAN_T_SIZE = 1 << ATAN_T_BITS;
-
-// N[Table[ArcTan[x], {x, 1/8, 8/8, 1/8}], 40]
-extern const double ATAN_T[ATAN_T_SIZE];
-extern const double ATAN_K[5];
-
-// The main idea of the function is to use formula
-// atan(u) + atan(v) = atan((u+v)/(1-uv))
-
-// x should be positive, normal finite value
-LIBC_INLINE double atan_eval(double x) {
-  using FPB = fputil::FPBits<double>;
-  using Sign = fputil::Sign;
-  // Added some small value to umin and umax mantissa to avoid possible rounding
-  // errors.
-  FPB::StorageType umin =
-      FPB::create_value(Sign::POS, FPB::EXP_BIAS - ATAN_T_BITS - 1,
-                        0x100000000000UL)
-          .uintval();
-  FPB::StorageType umax =
-      FPB::create_value(Sign::POS, FPB::EXP_BIAS + ATAN_T_BITS,
-                        0xF000000000000UL)
-          .uintval();
-
-  FPB bs(x);
-  auto x_abs = bs.abs().uintval();
-
-  if (x_abs <= umin) {
-    double pe = LIBC_NAMESPACE::fputil::polyeval(
-        x * x, 0.0, ATAN_K[1], ATAN_K[2], ATAN_K[3], ATAN_K[4]);
-    return fputil::multiply_add(pe, x, x);
-  }
-
-  if (x_abs >= umax) {
-    double one_over_x_m = -1.0 / x;
-    double one_over_x2 = one_over_x_m * one_over_x_m;
-    double pe = LIBC_NAMESPACE::fputil::polyeval(
-        one_over_x2, ATAN_K[0], ATAN_K[1], ATAN_K[2], ATAN_K[3]);
-    return fputil::multiply_add(pe, one_over_x_m,
-                                bs.is_neg() ? (-M_MATH_PI_2) : (M_MATH_PI_2));
-  }
+extern double ATAN_COEFFS[17][8];
 
-  double pos_x = FPB(x_abs).get_val();
-  bool one_over_x = pos_x > 1.0;
-  if (one_over_x) {
-    pos_x = 1.0 / pos_x;
-  }
+// For |x| <= 1/32 and 1 <= i <= 16, return Q(x) such that:
+//   Q(x) ~ (atan(x + i/16) - atan(i/16)) / x.
+LIBC_INLINE constexpr double atan_eval(double x, int i) {
+  double x2 = x * x;
 
-  double near_x = fputil::nearest_integer(pos_x * ATAN_T_SIZE);
-  int val = static_cast<int>(near_x);
-  near_x *= 1.0 / ATAN_T_SIZE;
+  double c0 = fputil::multiply_add(x, ATAN_COEFFS[i][2], ATAN_COEFFS[i][1]);
+  double c1 = fputil::multiply_add(x, ATAN_COEFFS[i][4], ATAN_COEFFS[i][3]);
+  double c2 = fputil::multiply_add(x, ATAN_COEFFS[i][6], ATAN_COEFFS[i][5]);
 
-  double v = (pos_x - near_x) / fputil::multiply_add(near_x, pos_x, 1.0);
-  double v2 = v * v;
-  double pe = LIBC_NAMESPACE::fputil::polyeval(v2, ATAN_K[0], ATAN_K[1],
-                                               ATAN_K[2], ATAN_K[3], ATAN_K[4]);
-  double result;
-  if (one_over_x)
-    result = M_MATH_PI_2 - fputil::multiply_add(pe, v, ATAN_T[val - 1]);
-  else
-    result = fputil::multiply_add(pe, v, ATAN_T[val - 1]);
-  return bs.is_neg() ? -result : result;
+  double x4 = x2 * x2;
+  double d1 = fputil::multiply_add(x2, c1, c0);
+  double d2 = fputil::multiply_add(x2, ATAN_COEFFS[i][7], c2);
+  double p = fputil::multiply_add(x4, d2, d1);
+  return p;
 }
 
 // > Q = fpminimax(asin(x)/x, [|0, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20|],
@@ -99,7 +46,7 @@ constexpr double ASIN_COEFFS[10] = {0x1.5555555540fa1p-3, 0x1.333333512edc2p-4,
                                     -0x1.df946fa875ddp-8, 0x1.02311ecf99c28p-5};
 
 // Evaluate P(x^2) - 1, where P(x^2) ~ asin(x)/x
-LIBC_INLINE double asin_eval(double xsq) {
+LIBC_INLINE constexpr double asin_eval(double xsq) {
   double x4 = xsq * xsq;
   double r1 = fputil::polyeval(x4, ASIN_COEFFS[0], ASIN_COEFFS[2],
                                ASIN_COEFFS[4], ASIN_COEFFS[6], ASIN_COEFFS[8]);
diff --git a/libc/test/src/math/exhaustive/atanf_test.cpp b/libc/test/src/math/exhaustive/atanf_test.cpp
index 508c288b050c55..6f23231d426741 100644
--- a/libc/test/src/math/exhaustive/atanf_test.cpp
+++ b/libc/test/src/math/exhaustive/atanf_test.cpp
@@ -25,7 +25,7 @@ TEST_F(LlvmLibcAtanfExhaustiveTest, PostiveRange) {
 }
 
 // Range: [-Inf, 0];
-static constexpr uint32_t NEG_START = 0xb000'0000U;
+static constexpr uint32_t NEG_START = 0x8000'0000U;
 static constexpr uint32_t NEG_STOP = 0xff80'0000U;
 
 TEST_F(LlvmLibcAtanfExhaustiveTest, NegativeRange) {
diff --git a/utils/bazel/llvm-project-overlay/libc/BUILD.bazel b/utils/bazel/llvm-project-overlay/libc/BUILD.bazel
index 073353a89c8907..fcc78c6f21544d 100644
--- a/utils/bazel/llvm-project-overlay/libc/BUILD.bazel
+++ b/utils/bazel/llvm-project-overlay/libc/BUILD.bazel
@@ -1234,13 +1234,9 @@ libc_support_library(
     hdrs = ["src/math/generic/inv_trigf_utils.h"],
     deps = [
         ":__support_common",
-        ":__support_fputil_fenv_impl",
         ":__support_fputil_fma",
-        ":__support_fputil_fp_bits",
         ":__support_fputil_multiply_add",
-        ":__support_fputil_nearest_integer",
         ":__support_fputil_polyeval",
-        ":math_utils",
     ],
 )
 

>From 2f489bf85dfc28685780fc8b1d8e889464b04f95 Mon Sep 17 00:00:00 2001
From: Tue Ly <lntue at google.com>
Date: Fri, 15 Mar 2024 17:43:58 -0400
Subject: [PATCH 2/2] Fix formatting.

---
 libc/src/math/generic/atanf.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libc/src/math/generic/atanf.cpp b/libc/src/math/generic/atanf.cpp
index 2ed5135c669348..cf0dbc1da667c5 100644
--- a/libc/src/math/generic/atanf.cpp
+++ b/libc/src/math/generic/atanf.cpp
@@ -7,6 +7,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "src/math/atanf.h"
+#include "inv_trigf_utils.h"
 #include "src/__support/FPUtil/FPBits.h"
 #include "src/__support/FPUtil/PolyEval.h"
 #include "src/__support/FPUtil/except_value_utils.h"
@@ -14,7 +15,6 @@
 #include "src/__support/FPUtil/nearest_integer.h"
 #include "src/__support/FPUtil/rounding_mode.h"
 #include "src/__support/macros/optimization.h" // LIBC_UNLIKELY
-#include "inv_trigf_utils.h"
 
 namespace LIBC_NAMESPACE {
 



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