replace integer multiplication or division with shift if one of multipliers or divisor is a power of 2 ------------------------------------------------------------------------------------------------------ Key: HARMONY-5901 URL: https://issues.apache.org/jira/browse/HARMONY-5901 Project: Harmony Issue Type: Improvement Components: DRLVM Reporter: Xiaoming Gu 1. Mulitiplication replacement a. It's about integer multiplication. b. One of two multipliers is a power of 2. c. The power of 2 could be negative. For example, 23*4 is transformed to 23<<2 and 23*(-4) is transformed to (23<<2)*(-1). 2. Division replacement a. It's about integer division. b. The divisor is a power of 2. c. The power of 2 could be negative. d. Because of round-up difference between division and shift right, the following equations from Aleksey are used. Baseline: q = a / (1 << d); Optimized: q = (a + [(1 << d) - 1] & (a >> 31)) >> d; For example, 23/4 is transformed to (23+((1<<2)-1)&(23>>31))>>2. and (-23)/(-4) is transformed to ((-23+((1<<2)-1)&(-23>>31))>>2)*(-1). 3. Comments for SAR and SHR swapped The comments for the two similar operations were misplaced in working_vm/vm/port/src/encoder/ia32_em64t. -- This message is automatically generated by JIRA. - You can reply to this email to add a comment to the issue online.