[libc][math] Fix signed zeros for powf when underflow happens. (llvm#…

…112601)
abidh · Oct 18, 2024 · 170dab9 · 170dab9
1 parent 629a182
commit 170dab9
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Showing 2 changed files with 6 additions and 3 deletions.
diff --git 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
@@ -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));
 }