LIB: fast_log2: make this a little faster by assuming positive input

Signed-off-by: Stefan Westerfeld <[email protected]>
swesterfeld · Jun 9, 2024 · 586de6d · 586de6d
1 parent 83c10aa
commit 586de6d
Showing 1 changed file with 1 addition and 1 deletion.
diff --git a/lib/smmath.hh b/lib/smmath.hh
@@ -594,7 +594,7 @@ fast_log2 (float *values, int n_values)
       for (int k = 0; k < todo; k++)
         {
           const int EXPONENT_MASK = 0x7F800000;
-          fexp[k] = ((values_i[k] & EXPONENT_MASK) >> 23) - FloatIEEE754::BIAS;    // extract exponent without bias
+          fexp[k] = (values_i[k] >> 23) - FloatIEEE754::BIAS;                      // extract exponent without bias (rely on sign bit == 0)
           values_i[k] = (values_i[k] & ~EXPONENT_MASK) | FloatIEEE754::BIAS << 23; // reset exponent to 2^0 so v_float is mantissa in [1..2]
         }
       for (int k = 0; k < todo; k++)