> CONFIG_FPU_ENABLE Y/N would correspond to --with-float=hard/soft, and > I believe setting CONFIG_IU_V8MULDIV to Y/N requires --with-cpu=V8/V7, > is that correct? I think it would make sense to build these as multilibs, > so the user can experiment to find out performance impacts of > the various hardware configurations on generated code. > > I wonder if it also would be worthwhile to have compiler options > for fpu=fast/slow and multiply=fast/slow, so we can schedule > appropriately. For the FPU, issue-rate/latency are as follows: > GR FPU: 1/4, with FDIV? 16 and FSQRT? 24 cycles, > non-pipelined on separate unit > GR FPU Lite: 8/8, with FDIVS/FDIVD/FSQRTS/FSQRTD 31/57/46/57 cycles, > non-pipelined on same unit
Let's not make this too complex for a first try, the settings used at AdaCore seem a good starting point to me. -- Eric Botcazou
