[libc-commits] [libc] 170dab9 - [libc][math] Fix signed zeros for powf when underflow happens. (#112601)

[via libc-commits]

Author: lntue
Date: 2024-10-18T14:26:05-04:00
New Revision: 170dab9972df3f6e905502db1846bb05fb444ec4

URL: https://github.com/llvm/llvm-project/commit/170dab9972df3f6e905502db1846bb05fb444ec4
DIFF: https://github.com/llvm/llvm-project/commit/170dab9972df3f6e905502db1846bb05fb444ec4.diff

LOG: [libc][math] Fix signed zeros for powf when underflow happens. (#112601)

Added: 
    

Modified: 
    libc/src/math/generic/powf.cpp
    libc/test/src/math/smoke/powf_test.cpp

Removed: 
    


################################################################################
diff  --git a/libc/src/math/generic/powf.cpp b/libc/src/math/generic/powf.cpp
index 8ce2465ba229cb..83477c6ef2aceb 100644
--- a/libc/src/math/generic/powf.cpp
+++ b/libc/src/math/generic/powf.cpp
@@ -855,9 +855,9 @@ LLVM_LIBC_FUNCTION(float, powf, (float x, float y)) {
           : 0.0;
   exp2_hi_mid_dd.hi = exp2_hi_mid;
 
-  return static_cast<float>(
-             powf_double_double(idx_x, dx, y6, lo6_hi, exp2_hi_mid_dd)) +
-         0.0f;
+  double r_dd = powf_double_double(idx_x, dx, y6, lo6_hi, exp2_hi_mid_dd);
+
+  return static_cast<float>(r_dd);
 }
 
 } // namespace LIBC_NAMESPACE_DECL

diff  --git a/libc/test/src/math/smoke/powf_test.cpp b/libc/test/src/math/smoke/powf_test.cpp
index bd4f98e30fbdc7..a0f66f2733a1ea 100644
--- a/libc/test/src/math/smoke/powf_test.cpp
+++ b/libc/test/src/math/smoke/powf_test.cpp
@@ -190,4 +190,7 @@ TEST_F(LlvmLibcPowfTest, SpecialNumbers) {
                                   FE_UNDERFLOW);
     }
   }
+
+  EXPECT_FP_EQ(-0.0f, LIBC_NAMESPACE::powf(-0.015625f, 25.0f));
+  EXPECT_FP_EQ(0.0f, LIBC_NAMESPACE::powf(-0.015625f, 26.0f));
 }