;; Faraday FA726TE Pipeline Description ;; Copyright (C) 2010-2021 Free Software Foundation, Inc. ;; Written by I-Jui Sung, based on ARM926EJ-S Pipeline Description. ;; ;; This file is part of GCC. ;; ;; GCC is free software; you can redistribute it and/or modify it under ;; the terms of the GNU General Public License as published by the Free ;; Software Foundation; either version 3, or (at your option) any later ;; version. ;; ;; GCC is distributed in the hope that it will be useful, but WITHOUT ANY ;; WARRANTY; without even the implied warranty of MERCHANTABILITY or ;; FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License ;; for more details. ;; ;; You should have received a copy of the GNU General Public License ;; along with GCC; see the file COPYING3. If not see ;; http://www.gnu.org/licenses/. */

;; These descriptions are based on the information contained in the ;; FA726TE Core Design Note, Copyright (c) 2010 Faraday Technology Corp.

;; This automaton provides a pipeline description for the Faraday ;; FA726TE core. ;; ;; The model given here assumes that the condition for all conditional ;; instructions is “true”, i.e., that all of the instructions are ;; actually executed.

(define_automaton “fa726te”)

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ;; Pipelines ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

;; The ALU pipeline has fetch, decode, execute, memory, and ;; write stages. We only need to model the execute, memory and write ;; stages.

;; E1 E2 E3 E4 E5 WB ;;______________________________________________________ ;; ;; <-------------- LD/ST -----------> ;; shifter + LU <-- AU --> ;; <-- AU --> shifter + LU CPSR (Pipe 0) ;;______________________________________________________ ;; ;; <---------- MUL ---------> ;; shifter + LU <-- AU --> ;; <-- AU --> shifter + LU CPSR (Pipe 1)

(define_cpu_unit “fa726te_alu0_pipe,fa726te_alu1_pipe” “fa726te”) (define_cpu_unit “fa726te_mac_pipe” “fa726te”) (define_cpu_unit “fa726te_lsu_pipe_e,fa726te_lsu_pipe_w” “fa726te”)

;; Pretend we have 2 LSUs (the second is ONLY for LDR), which can possibly ;; improve code quality. (define_query_cpu_unit “fa726te_lsu1_pipe_e,fa726te_lsu1_pipe_w” “fa726te”) (define_cpu_unit “fa726te_is0,fa726te_is1” “fa726te”)

(define_reservation “fa726te_issue” “(fa726te_is0|fa726te_is1)”) ;; Reservation to restrict issue to 1. (define_reservation “fa726te_blockage” “(fa726te_is0+fa726te_is1)”)

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ;; ALU Instructions ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

;; ALU instructions require three cycles to execute, and use the ALU ;; pipeline in each of the three stages. The results are available ;; after the execute stage has finished. ;; ;; If the destination register is the PC, the pipelines are stalled ;; for several cycles. That case is not modeled here.

;; Move instructions. (define_insn_reservation “726te_shift_op” 1 (and (eq_attr “tune” “fa726te”) (eq_attr “type” “mov_imm,mov_reg,mov_shift,mov_shift_reg,
mvn_imm,mvn_reg,mvn_shift,mvn_shift_reg”)) “fa726te_issue+(fa726te_alu0_pipe|fa726te_alu1_pipe)”)

;; ALU operations with no shifted operand will finished in 1 cycle ;; Other ALU instructions 2 cycles. (define_insn_reservation “726te_alu_op” 1 (and (eq_attr “tune” “fa726te”) (eq_attr “type” “alu_imm,alus_imm,logic_imm,logics_imm,
alu_sreg,alus_sreg,logic_reg,logics_reg,
adc_imm,adcs_imm,adc_reg,adcs_reg,
adr,bfm,rev,
shift_imm,shift_reg,
mrs,multiple”)) “fa726te_issue+(fa726te_alu0_pipe|fa726te_alu1_pipe)”)

;; ALU operations with a shift-by-register operand. ;; These really stall in the decoder, in order to read the shift value ;; in the first cycle. If the instruction uses both shifter and AU, ;; it takes 3 cycles. (define_insn_reservation “726te_alu_shift_op” 3 (and (eq_attr “tune” “fa726te”) (eq_attr “type” “extend,alu_shift_imm_lsl_1to4,alu_shift_imm_other,alus_shift_imm,
logic_shift_imm,logics_shift_imm”)) “fa726te_issue+(fa726te_alu0_pipe|fa726te_alu1_pipe)”)

(define_insn_reservation “726te_alu_shift_reg_op” 3 (and (eq_attr “tune” “fa726te”) (eq_attr “type” “alu_shift_reg,alus_shift_reg,
logic_shift_reg,logics_shift_reg”)) “fa726te_issue+(fa726te_alu0_pipe|fa726te_alu1_pipe)”) ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ;; Multiplication Instructions ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

;; Multiplication instructions loop in the execute stage until the ;; instruction has been passed through the multiplier array enough ;; times. Multiply operations occur in both the execute and memory ;; stages of the pipeline

(define_insn_reservation “726te_mult_op” 3 (and (eq_attr “tune” “fa726te”) (eq_attr “type” “smlalxy,mul,mla,muls,mlas,umull,umlal,smull,smlal,
umulls,umlals,smulls,smlals,smlawx,smulxy,smlaxy”)) “fa726te_issue+fa726te_mac_pipe”)

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ;; Load/Store Instructions ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

;; The models for load/store instructions do not accurately describe ;; the difference between operations with a base register writeback ;; (such as “ldm!”). These models assume that all memory references ;; hit in dcache.

;; Loads with a shifted offset take 3 cycles, and are (a) probably the ;; most common and (b) the pessimistic assumption will lead to fewer stalls.

;; Scalar loads are pipelined in FA726TE LSU pipe. ;; Here we model the resource conflict between Load@E3-stage & Store@W-stage. ;; The 2nd LSU (lsu1) is to model the fact that if 2 loads are scheduled in the ;; same “bundle”, and the 2nd load will introudce another ISSUE stall but is ;; still ok to execute (and may be benefical sometimes).

(define_insn_reservation “726te_load1_op” 3 (and (eq_attr “tune” “fa726te”) (eq_attr “type” “load_4,load_byte”)) “(fa726te_issue+fa726te_lsu_pipe_e+fa726te_lsu_pipe_w)
| (fa726te_issue+fa726te_lsu1_pipe_e+fa726te_lsu1_pipe_w,fa726te_blockage)”)

(define_insn_reservation “726te_store1_op” 1 (and (eq_attr “tune” “fa726te”) (eq_attr “type” “store_4”)) “fa726te_blockage*2”)

;; Load/Store Multiple blocks all pipelines in EX stages until WB. ;; No other instructions can be issued together. Since they essentially ;; prevent all scheduling opportunities, we model them together here.

;; The LDM is breaking into multiple load instructions, later instruction in ;; the pipe 1 is stalled. (define_insn_reservation “726te_ldm2_op” 4 (and (eq_attr “tune” “fa726te”) (eq_attr “type” “load_8,load_12”)) “fa726te_blockage*4”)

(define_insn_reservation “726te_ldm3_op” 5 (and (eq_attr “tune” “fa726te”) (eq_attr “type” “load_16”)) “fa726te_blockage*5”)

(define_insn_reservation “726te_stm2_op” 2 (and (eq_attr “tune” “fa726te”) (eq_attr “type” “store_8,store_12”)) “fa726te_blockage*3”)

(define_insn_reservation “726te_stm3_op” 3 (and (eq_attr “tune” “fa726te”) (eq_attr “type” “store_16”)) “fa726te_blockage*4”)

(define_bypass 1 “726te_load1_op,726te_ldm2_op,726te_ldm3_op” “726te_store1_op,
726te_stm2_op,726te_stm3_op” “arm_no_early_store_addr_dep”) (define_bypass 0 “726te_shift_op,726te_alu_op,726te_alu_shift_op,
726te_alu_shift_reg_op,726te_mult_op” “726te_store1_op” “arm_no_early_store_addr_dep”) (define_bypass 0 “726te_shift_op,726te_alu_op” “726te_shift_op,726te_alu_op”) (define_bypass 1 “726te_alu_shift_op,726te_alu_shift_reg_op” “726te_shift_op,726te_alu_op”) (define_bypass 1 “726te_alu_shift_op,726te_alu_shift_reg_op,726te_mult_op” “726te_alu_shift_op” “arm_no_early_alu_shift_dep”) (define_bypass 1 “726te_alu_shift_op,726te_alu_shift_reg_op,726te_mult_op” “726te_alu_shift_reg_op” “arm_no_early_alu_shift_value_dep”) (define_bypass 1 “726te_mult_op” “726te_shift_op,726te_alu_op”)

(define_bypass 4 “726te_load1_op” “726te_mult_op”) (define_bypass 5 “726te_ldm2_op” “726te_mult_op”) (define_bypass 6 “726te_ldm3_op” “726te_mult_op”)

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ;; Branch and Call Instructions ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

;; Branch instructions are difficult to model accurately. The FA726TE ;; core can predict most branches. If the branch is predicted ;; correctly, and predicted early enough, the branch can be completely ;; eliminated from the instruction stream. Some branches can ;; therefore appear to require zero cycle to execute. We assume that ;; all branches are predicted correctly, and that the latency is ;; therefore the minimum value.

(define_insn_reservation “726te_branch_op” 0 (and (eq_attr “tune” “fa726te”) (eq_attr “type” “branch”)) “fa726te_blockage”)

;; The latency for a call is actually the latency when the result is available. ;; i.e. R0 is ready for int return value. (define_insn_reservation “726te_call_op” 1 (and (eq_attr “tune” “fa726te”) (eq_attr “type” “call”)) “fa726te_blockage”)