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  1. JDK
  2. JDK-8222029

Optimize Math.floorMod

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    • b16

    Description

      Currently Math.floorMod is implemented as: return x - floorDiv(x, y) * y;

      This can be optimized as:

              int mod = x % y;
              // if the signs are different and modulo not zero, adjust result
              if ((mod ^ y) < 0 && mod != 0) {
                  mod += y;
              }
              return mod;

      While the JIT does a reasonably good job at the current implementation, this ensures we only do a single integer division and no subsequent integer multiplications, speeding up execution by ~1.3x in interpreter (mainly from removing the floorDiv method call overhead) and ~1.1x with C1 and C2.

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