nir,aco,pan/bi: optimize ddx_fine(a) * ddx_fine(a)
Foz-DB Navi31:
Totals from 436 (0.55% of 79395) affected shaders:
Instrs: 808917 -> 805868 (-0.38%)
CodeSize: 4269056 -> 4246512 (-0.53%)
Latency: 5827077 -> 5819815 (-0.12%); split: -0.13%, +0.00%
InvThroughput: 625482 -> 622959 (-0.40%); split: -0.41%, +0.00%
SClause: 21797 -> 21756 (-0.19%); split: -0.23%, +0.04%
Copies: 48502 -> 48505 (+0.01%); split: -0.04%, +0.05%
VALU: 481686 -> 479074 (-0.54%); split: -0.54%, +0.00%
SALU: 76699 -> 76700 (+0.00%)