I have a question about *unfused* fma instructions. MIPS has processors with both fused and unfused multiple and add instructions and for fused madd's it is clear what to do; define 'fma' instructions in the md file and let convert_mult_to_fma decide whether or not to use them.
But for non-fused multiply and adds, it is less clear. One could define '*madd' instructions with the plus and mult operator and let the peephole optimizer convert normal expressions that have these operators into (unfused) instructions. This is what MIPS currently does. Or one could change convert_mult_to_fma to add a check if fma is fused vs. non-fused in addition to the check for the flag_fp_contract_mode in order to decide whether to convert expressions into an fma and then define fma instructions in the md file. I was wondering if anyone had an opinion about the advantages or disadvantages of these two approaches. Steve Ellcey sell...@imgtec.com
