gcc/config/arm/arm1026ejs.md

;; ARM 1026EJ-S Pipeline Description ;; Copyright (C) 2003-2021 Free Software Foundation, Inc. ;; Written by CodeSourcery, LLC. ;; ;; 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/. */

;; This automaton provides a pipeline description for the ARM ;; 1026EJ-S 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 “arm1026ejs”)

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

;; There are two pipelines: ;; ;; - An Arithmetic Logic Unit (ALU) pipeline. ;; ;; The ALU pipeline has fetch, issue, decode, execute, memory, and ;; write stages. We only need to model the execute, memory and write ;; stages. ;; ;; - A Load-Store Unit (LSU) pipeline. ;; ;; The LSU pipeline has decode, execute, memory, and write stages. ;; We only model the execute, memory and write stages.

(define_cpu_unit “a_e,a_m,a_w” “arm1026ejs”) (define_cpu_unit “l_e,l_m,l_w” “arm1026ejs”)

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ;; 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.

;; ALU operations with no shifted operand (define_insn_reservation “alu_op” 1 (and (eq_attr “tune” “arm1026ejs”) (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,
mov_imm,mov_reg,mvn_imm,mvn_reg,
multiple”)) “a_e,a_m,a_w”)

;; ALU operations with a shift-by-constant operand (define_insn_reservation “alu_shift_op” 1 (and (eq_attr “tune” “arm1026ejs”) (eq_attr “type” “alu_shift_imm_lsl_1to4,alu_shift_imm_other,alus_shift_imm,
logic_shift_imm,logics_shift_imm,
extend,mov_shift,mvn_shift”)) “a_e,a_m,a_w”)

;; ALU operations with a shift-by-register operand ;; These really stall in the decoder, in order to read ;; the shift value in a second cycle. Pretend we take two cycles in ;; the execute stage. (define_insn_reservation “alu_shift_reg_op” 2 (and (eq_attr “tune” “arm1026ejs”) (eq_attr “type” “alu_shift_reg,alus_shift_reg,
logic_shift_reg,logics_shift_reg,
mov_shift_reg,mvn_shift_reg”)) “a_e*2,a_m,a_w”)

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ;; Multiplication Instructions ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

;; Multiplication instructions loop in the execute stage until the ;; instruction has been passed through the multiplier array enough ;; times.

;; The result of the “smul” and “smulw” instructions is not available ;; until after the memory stage. (define_insn_reservation “mult1” 2 (and (eq_attr “tune” “arm1026ejs”) (eq_attr “type” “smulxy,smulwy”)) “a_e,a_m,a_w”)

;; The “smlaxy” and “smlawx” instructions require two iterations through ;; the execute stage; the result is available immediately following ;; the execute stage. (define_insn_reservation “mult2” 2 (and (eq_attr “tune” “arm1026ejs”) (eq_attr “type” “smlaxy,smlalxy,smlawx”)) “a_e*2,a_m,a_w”)

;; The “smlalxy”, “mul”, and “mla” instructions require two iterations ;; through the execute stage; the result is not available until after ;; the memory stage. (define_insn_reservation “mult3” 3 (and (eq_attr “tune” “arm1026ejs”) (eq_attr “type” “smlalxy,mul,mla”)) “a_e*2,a_m,a_w”)

;; The “muls” and “mlas” instructions loop in the execute stage for ;; four iterations in order to set the flags. The value result is ;; available after three iterations. (define_insn_reservation “mult4” 3 (and (eq_attr “tune” “arm1026ejs”) (eq_attr “type” “muls,mlas”)) “a_e*4,a_m,a_w”)

;; Long multiply instructions that produce two registers of ;; output (such as umull) make their results available in two cycles; ;; the least significant word is available before the most significant ;; word. That fact is not modeled; instead, the instructions are ;; described as if the entire result was available at the end of the ;; cycle in which both words are available.

;; The “umull”, “umlal”, “smull”, and “smlal” instructions all take ;; three iterations through the execute cycle, and make their results ;; available after the memory cycle. (define_insn_reservation “mult5” 4 (and (eq_attr “tune” “arm1026ejs”) (eq_attr “type” “umull,umlal,smull,smlal”)) “a_e*3,a_m,a_w”)

;; The “umulls”, “umlals”, “smulls”, and “smlals” instructions loop in ;; the execute stage for five iterations in order to set the flags. ;; The value result is available after four iterations. (define_insn_reservation “mult6” 4 (and (eq_attr “tune” “arm1026ejs”) (eq_attr “type” “umulls,umlals,smulls,smlals”)) “a_e*5,a_m,a_w”)

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ;; 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.

;; LSU instructions require six cycles to execute. They use the ALU ;; pipeline in all but the 5th cycle, and the LSU pipeline in cycles ;; three through six. ;; Loads and stores which use a scaled register offset or scaled ;; register pre-indexed addressing mode take three cycles EXCEPT for ;; those that are base + offset with LSL of 0 or 2, or base - offset ;; with LSL of zero. The remainder take 1 cycle to execute. ;; For 4byte loads there is a bypass from the load stage

(define_insn_reservation “load1_op” 2 (and (eq_attr “tune” “arm1026ejs”) (eq_attr “type” “load_byte,load_4”)) “a_e+l_e,l_m,a_w+l_w”)

(define_insn_reservation “store1_op” 0 (and (eq_attr “tune” “arm1026ejs”) (eq_attr “type” “store_4”)) “a_e+l_e,l_m,a_w+l_w”)

;; A load's result can be stored by an immediately following store (define_bypass 1 “load1_op” “store1_op” “arm_no_early_store_addr_dep”)

;; On a LDM/STM operation, the LSU pipeline iterates until all of the ;; registers have been processed. ;; ;; The time it takes to load the data depends on whether or not the ;; base address is 64-bit aligned; if it is not, an additional cycle ;; is required. This model assumes that the address is always 64-bit ;; aligned. Because the processor can load two registers per cycle, ;; that assumption means that we use the same instruction reservations ;; for loading 2k and 2k - 1 registers. ;; ;; The ALU pipeline is stalled until the completion of the last memory ;; stage in the LSU pipeline. That is modeled by keeping the ALU ;; execute stage busy until that point. ;; ;; As with ALU operations, if one of the destination registers is the ;; PC, there are additional stalls; that is not modeled.

(define_insn_reservation “load2_op” 2 (and (eq_attr “tune” “arm1026ejs”) (eq_attr “type” “load_8”)) “a_e+l_e,l_m,a_w+l_w”)

(define_insn_reservation “store2_op” 0 (and (eq_attr “tune” “arm1026ejs”) (eq_attr “type” “store_8”)) “a_e+l_e,l_m,a_w+l_w”)

(define_insn_reservation “load34_op” 3 (and (eq_attr “tune” “arm1026ejs”) (eq_attr “type” “load_12,load_16”)) “a_e+l_e,a_e+l_e+l_m,a_e+l_m,a_w+l_w”)

(define_insn_reservation “store34_op” 0 (and (eq_attr “tune” “arm1026ejs”) (eq_attr “type” “store_12,store_16”)) “a_e+l_e,a_e+l_e+l_m,a_e+l_m,a_w+l_w”)

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

;; Branch instructions are difficult to model accurately. The ARM ;; 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 cycles to execute. We assume that ;; all branches are predicted correctly, and that the latency is ;; therefore the minimum value.

(define_insn_reservation “branch_op” 0 (and (eq_attr “tune” “arm1026ejs”) (eq_attr “type” “branch”)) “nothing”)

;; The latency for a call is not predictable. Therefore, we use 32 as ;; roughly equivalent to positive infinity.

(define_insn_reservation “call_op” 32 (and (eq_attr “tune” “arm1026ejs”) (eq_attr “type” “call”)) “nothing”)