Hello All, I need some help with setting the pipeline hazard recognizer (I am working with gcc v4.5.1 for a private target).
A brief pipeline description of my target: We have 2 functional units 1) For multiplication. 2) For All other instructions. a) Multiply instructions are not pipelined. b) It takes 4 cycles to execute a multiply instruction. c) The result of multiply instruction will be available after 4 cycles. So there should be a 4 cycle gap between 2 multiply instructions (independent/dependent) and also its depend instructions (other than multiply). e.g.1: mult R3, R4, R5 -- (A) add R0, R1, R2 mult R7, R8, R9 -- (B) A) & (B) are independent. This is a pipeline error. Need to add 2 NOP's or schedule 2 other independent instructions before (B). e.g.2: mult R3, R4, R5 --(A) add R7, R8, R9 add R5, R1, R2 --(B) (A) & (B) are dependent. Even though there is no pipeline error, the value of "R5" used will not be the updated one as 'mult' takes 4 cycles for the result to be available. Need to add 2 NOP's or schedule 2 other independent instructions before (B). I have done the following, but not sure if this will take care of: A) 4 cycle gap between 2 Independent multiply instructions B) 4 cycle gap beween multiply and any other dependent instruction. (define_automaton "pipeline") (define_cpu_unit "simple" "pipeline") (define_cpu_unit "mult" "pipeline") (define_insn_reservation "any_insn" 1 (eq_attr "type" "!mul") "simple") (define_insn_reservation "mult" 4 (eq_attr "type" "mul") "mult*4") In case other independent instructions are not available to be scheduled for this latency, i will be inserting NOP's from the backend. But i want to make sure the correct info is passed to the scheduler. Any comments/suggestions? Thanks, Rohit
