Description
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.
Attachments
Attachments
Issue Links
- incorporates
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HARMONY-5965 [drlvm][jit]generate Mnemonic_LEA LIR for Op_Shladd HIR in IA32
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- Closed
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