Short waits with umwait

Posted Jun 17, 2019 2:48 UTC (Mon) by ncm (guest, #165)
In reply to: Short waits with umwait by caliloo
Parent article: Short waits with umwait

It occurs to me that there is really no need for this instruction -- micro-op fusion ought to recognize a busy-wait loop, and translate it internally.

Since Haswell, Intel already does fusion of two ALU instructions and two branches to one cycle -- on a good day, anyway; when I last checked, Clang was very bad at putting instructions in the right order to get this.