[LLVMdev] Artificial deps and stores
hfinkel at anl.gov
Fri Jan 17 15:54:18 PST 2014
Andy, et al.,
In ScheduleDAGInstrs::buildSchedGraph, the code for handling stores has this:
// Push store's up a bit to avoid them getting in between cmp
// and branches.
This code does not seem to be in any way specific to compares; and in any case, at least on the PPC A2, scheduling stores in between the compare and the branch would not be a bad thing (because the core is in order, and the compare has a 2-cycle latency, so if there is nothing else to do, a store would not be a bad thing to put there).
Can you explain the motivation for this (why or for what it is bad), and what else it might do (aside from the commented cmp/branch pairing)? I'm wondering if we should make this target dependent.
Assistant Computational Scientist
Leadership Computing Facility
Argonne National Laboratory
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