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> Attached RFC patch implements reciprocal pass that converts sqrt to > rsqrt. The pass converts several forms of sqrt: > > a / sqrt(b / c) => a * rsqrt (c / b) > > sqrt (a / b) => rsqrt ( b / a) > > sqrt (a) => a * rsqrt (a)
Um, no. At least the SSE rsqrt instructions have only results accurate to 12bits, they are not meant to be used by themself. I would be against such transformation _even_ with unsafe-math-optims.
This is referenced to an early RFC patch. Final version has NR enhancement step and works OK with adequate precision.
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