[libc] Fix signed zeros for exp10m1f16 and tanhf16.

[lntue]

No description provided.

[llvmbot]

@llvm/pr-subscribers-libc

Author: None (lntue)

Changes

---

Full diff: https://github.com/llvm/llvm-project/pull/116654.diff

1 Files Affected:

• (modified) libc/src/math/generic/exp10m1f16.cpp (+3)

diff --git a/libc/src/math/generic/exp10m1f16.cpp b/libc/src/math/generic/exp10m1f16.cpp
index 9f2c1959fa5ec9..449aedf254ca50 100644
--- a/libc/src/math/generic/exp10m1f16.cpp
+++ b/libc/src/math/generic/exp10m1f16.cpp
@@ -119,6 +119,9 @@ LLVM_LIBC_FUNCTION(float16, exp10m1f16, (float16 x)) {
 
     // When |x| <= 2^(-3).
     if (x_abs <= 0x3000U) {
+      if (LIBC_UNLIKELY(x_abs == 0))
+        return x;
+
       if (auto r = EXP10M1F16_EXCEPTS_LO.lookup(x_u);
           LIBC_UNLIKELY(r.has_value()))
         return r.value();

[jhuber6]

Thanks