[libc-commits] [libc] [libc][math][c23] Add f16fmaf C23 math function (PR #95483)

[via libc-commits]

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@@ -198,46 +230,40 @@ template <> LIBC_INLINE double fma<double>(double x, double y, double z) {
     }
   }
 
-  uint64_t result = 0;
+  OutStorageType result = 0;
   int r_exp = 0; // Unbiased exponent of the result
 
   // Normalize the result.
   if (prod_mant != 0) {
-    uint64_t prod_hi = static_cast<uint64_t>(prod_mant >> 64);
-    int lead_zeros =
-        prod_hi ? cpp::countl_zero(prod_hi)
-                : 64 + cpp::countl_zero(static_cast<uint64_t>(prod_mant));
+    int lead_zeros = cpp::countl_zero(prod_mant);
     // Move the leading 1 to the most significant bit.
     prod_mant <<= lead_zeros;
-    // The lower 64 bits are always sticky bits after moving the leading 1 to
-    // the most significant bit.
-    sticky_bits |= (static_cast<uint64_t>(prod_mant) != 0);
-    result = static_cast<uint64_t>(prod_mant >> 64);
-    // Change prod_lsb_exp the be the exponent of the least significant bit of
-    // the result.
-    prod_lsb_exp += 64 - lead_zeros;
-    r_exp = prod_lsb_exp + 63;
+    prod_lsb_exp -= lead_zeros;
+    r_exp = prod_lsb_exp + (cpp::numeric_limits<TmpResultType>::digits - 1) -
+            InFPBits::EXP_BIAS + OutFPBits::EXP_BIAS;
 
     if (r_exp > 0) {
       // The result is normal.  We will shift the mantissa to the right by
       // 63 - 52 = 11 bits (from the locations of the most significant bit).
       // Then the rounding bit will correspond the 11th bit, and the lowest
       // 10 bits are merged into sticky bits.
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overmighty wrote:

I need to update these comments.

https://github.com/llvm/llvm-project/pull/95483