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1. Use bseti when profitable.  Many cases of poor constant synthesis are failure to use bseti.
2. Use "uw" variants of shifts/arithmetic instructions when the constant has bit 0x80000000 set.
3. Use shNadd for constants evenly divisible by 9, 5 or 3.
4. Use blcri in conjunction with lui or addi to clear a small number of bits, particularly in the high 33 bits of a 64bit word
5. Adjust constant so low 13 bits are 0x1800, recursively re-synthesize and restore low bits with trailing addi.
6. Synthesize C' from C using bit inversion.  Synthesize C', then invert the result.  If that's better than synthesizing C directly, then use the inversion sequence.
7. Use pack for repeating constants
   1. Depends on reassociation of constant in logical ops with shifts
   2. Depends on basic Zbkb support
8. Use pack as synthesis of last resort.

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RISE:

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Updates

02 Jun 2024

• Project done. 

30 May 2024

•  zbkb as synthesis of last support submitted upstream for CI testing
• Additional ideas for improvements in constant synthesis pushed to 2H2024.

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