[libc-commits] [libc] Add sinf16 function (PR #116674)

[via libc-commits]

================
@@ -62,20 +62,21 @@ LLVM_LIBC_FUNCTION(float16, sinf16, (float16 x)) {
       return r.value();
   }
 
-  // Exhaustive tests show that for |x| <= 0x13d0, 1ULP rounding errors occur.
-  // To fix this, the following apply:
-  // - When x >= 0, and rounding upward, sin(x) == x.
-  // - When x < 0, and rounding downward, sin(x) == x.
-  // - When x < 0, and rounding upward, sin(x) == (x - 1ULP)
   int rounding = fputil::quick_get_round();
+
+  // Exhaustive tests show that for |x| <= 0x1.f4p-11, 1ULP rounding errors
+  // occur. To fix this, the following apply:
   if (LIBC_UNLIKELY(x_abs <= 0x13d0)) {
+    // When x >= 0, and rounding upward, sin(x) == x.
     if (LIBC_UNLIKELY(x_abs == 0U))
       return x;
 
+    // When x < 0, and rounding downward, sin(x) == x.
     if ((rounding == FE_UPWARD && xbits.is_pos()) ||
         (rounding == FE_DOWNWARD && xbits.is_neg()))
       return x;
----------------
overmighty wrote:

The comments don't seem to match the code here.

```suggestion
    // sin(+/-0) = +/-0
    if (LIBC_UNLIKELY(x_abs == 0U))
      return x;

    // When x > 0, and rounding upward, sin(x) == x.
    // When x < 0, and rounding downward, sin(x) == x.
    if ((rounding == FE_UPWARD && xbits.is_pos()) ||
        (rounding == FE_DOWNWARD && xbits.is_neg()))
      return x;
```

https://github.com/llvm/llvm-project/pull/116674