Doug Moore
38f5cb1bfb
The clev field in the node struct is almost always multiplied by WIDTH; occasionally, it is incremented and then multiplied by WIDTH. Instructions can be saved by storing it always multiplied by WIDTH. For the computation of slot(), this just eliminates a multiplication. For trimkey(), where the caller always adds one to clev before passing it as an argument, this change has the caller, not the caller, do that. Trimkey() handles it not by adding WIDTH to the input parameter, but by shifting COUNT, and not 1. That produces the same result, and it relieves keybarr of the need to test to avoid shifting by more than 63 bits, since level is always <= 63. This takes 3 instrutions and 14 bytes out of the basic lookup loop on amd64. Reviewed by: kib Tested by: pho (as part of a larger change) Differential Revision: https://reviews.freebsd.org/D41226
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