From 4ee5be6f755ea9e36c44657cd5fa587e13b11ddc Mon Sep 17 00:00:00 2001
From: OverMighty <its.overmighty@gmail.com>
Date: Tue, 15 Oct 2024 16:58:28 +0200
Subject: [PATCH] Migrate to fputil::cast

---
 libc/src/math/generic/CMakeLists.txt      |  1 +
 libc/src/math/generic/log2f16.cpp         | 11 ++++++-----
 libc/test/src/math/smoke/CMakeLists.txt   |  1 +
 libc/test/src/math/smoke/log2f16_test.cpp |  9 ++++++---
 4 files changed, 14 insertions(+), 8 deletions(-)

diff --git a/libc/src/math/generic/CMakeLists.txt b/libc/src/math/generic/CMakeLists.txt
index 0bde9ff12a4588..0fbe99405aaef1 100644
--- a/libc/src/math/generic/CMakeLists.txt
+++ b/libc/src/math/generic/CMakeLists.txt
@@ -2241,6 +2241,7 @@ add_entrypoint_object(
     .expxf16
     libc.hdr.errno_macros
     libc.hdr.fenv_macros
+    libc.src.__support.FPUtil.cast
     libc.src.__support.FPUtil.except_value_utils
     libc.src.__support.FPUtil.fenv_impl
     libc.src.__support.FPUtil.fp_bits
diff --git a/libc/src/math/generic/log2f16.cpp b/libc/src/math/generic/log2f16.cpp
index d72bc99d939ead..af84a1f1322467 100644
--- a/libc/src/math/generic/log2f16.cpp
+++ b/libc/src/math/generic/log2f16.cpp
@@ -13,6 +13,7 @@
 #include "src/__support/FPUtil/FEnvImpl.h"
 #include "src/__support/FPUtil/FPBits.h"
 #include "src/__support/FPUtil/PolyEval.h"
+#include "src/__support/FPUtil/cast.h"
 #include "src/__support/FPUtil/except_value_utils.h"
 #include "src/__support/FPUtil/multiply_add.h"
 #include "src/__support/common.h"
@@ -112,11 +113,11 @@ LLVM_LIBC_FUNCTION(float16, log2f16, (float16 x)) {
 
   int m = -FPBits::EXP_BIAS;
 
-  // When x is subnormal.
+  // When x is subnormal, normalize it.
   if ((x_u & FPBits::EXP_MASK) == 0U) {
-    // Normalize x.
-    x_bits = FPBits(x_bits.get_val() *
-                    static_cast<float16>((1U << FPBits::FRACTION_LEN)));
+    // Can't pass an integer to fputil::cast directly.
+    constexpr float NORMALIZE_EXP = 1U << FPBits::FRACTION_LEN;
+    x_bits = FPBits(x_bits.get_val() * fputil::cast<float16>(NORMALIZE_EXP));
     x_u = x_bits.uintval();
     m -= FPBits::FRACTION_LEN;
   }
@@ -142,7 +143,7 @@ LLVM_LIBC_FUNCTION(float16, log2f16, (float16 x)) {
       v * fputil::polyeval(v, 0x1.715476p+0f, -0x1.71771ap-1f, 0x1.ecb38ep-2f);
   // log2(1.mant) = log2(f) + log2(1 + d/f)
   float log2_1_mant = LOG2F_F[f] + log2p1_d_over_f;
-  return static_cast<float16>(static_cast<float>(m) + log2_1_mant);
+  return fputil::cast<float16>(static_cast<float>(m) + log2_1_mant);
 }
 
 } // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/test/src/math/smoke/CMakeLists.txt b/libc/test/src/math/smoke/CMakeLists.txt
index 66f442c6c4d407..4f1cf3d78f7de2 100644
--- a/libc/test/src/math/smoke/CMakeLists.txt
+++ b/libc/test/src/math/smoke/CMakeLists.txt
@@ -3594,6 +3594,7 @@ add_fp_unittest(
     libc.hdr.fenv_macros
     libc.src.errno.errno
     libc.src.math.log2f16
+    libc.src.__support.FPUtil.cast
 )
 
 add_fp_unittest(
diff --git a/libc/test/src/math/smoke/log2f16_test.cpp b/libc/test/src/math/smoke/log2f16_test.cpp
index 3e0dda69f805d0..6d98482aa44996 100644
--- a/libc/test/src/math/smoke/log2f16_test.cpp
+++ b/libc/test/src/math/smoke/log2f16_test.cpp
@@ -7,6 +7,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "hdr/fenv_macros.h"
+#include "src/__support/FPUtil/cast.h"
 #include "src/errno/libc_errno.h"
 #include "src/math/log2f16.h"
 #include "test/UnitTest/FPMatcher.h"
@@ -37,11 +38,13 @@ TEST_F(LlvmLibcLog2f16Test, SpecialNumbers) {
       neg_inf, LIBC_NAMESPACE::log2f16(neg_zero), FE_DIVBYZERO);
   EXPECT_MATH_ERRNO(0);
 
-  EXPECT_FP_EQ_ALL_ROUNDING(zero,
-                            LIBC_NAMESPACE::log2f16(static_cast<float16>(1.0)));
+  EXPECT_FP_EQ_ALL_ROUNDING(
+      zero,
+      LIBC_NAMESPACE::log2f16(LIBC_NAMESPACE::fputil::cast<float16>(1.0)));
   EXPECT_MATH_ERRNO(0);
 
   EXPECT_FP_EQ_ALL_ROUNDING(
-      aNaN, LIBC_NAMESPACE::log2f16(static_cast<float16>(-1.0)));
+      aNaN,
+      LIBC_NAMESPACE::log2f16(LIBC_NAMESPACE::fputil::cast<float16>(-1.0)));
   EXPECT_MATH_ERRNO(EDOM);
 }