;; ARM 1020E & ARM 1022E Pipeline Description ;; Copyright (C) 2005 Free Software Foundation, Inc. ;; Contributed by Richard Earnshaw (richard.earnshaw@arm.com) ;; ;; 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 2, 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 COPYING. If not, write to the Free ;; Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA ;; 02110-1301, USA. */

;; These descriptions are based on the information contained in the ;; ARM1020E Technical Reference Manual, Copyright (c) 2003 ARM ;; Limited. ;;

;; This automaton provides a pipeline description for the ARM ;; 1020E 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 “arm1020e”)

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ;; 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 “1020a_e,1020a_m,1020a_w” “arm1020e”) (define_cpu_unit “1020l_e,1020l_m,1020l_w” “arm1020e”)

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ;; 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 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 “1020alu_op” 1 (and (eq_attr “tune” “arm1020e,arm1022e”) (eq_attr “type” “alu”)) “1020a_e,1020a_m,1020a_w”)

;; ALU operations with a shift-by-constant operand (define_insn_reservation “1020alu_shift_op” 1 (and (eq_attr “tune” “arm1020e,arm1022e”) (eq_attr “type” “alu_shift”)) “1020a_e,1020a_m,1020a_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 “1020alu_shift_reg_op” 2 (and (eq_attr “tune” “arm1020e,arm1022e”) (eq_attr “type” “alu_shift_reg”)) “1020a_e*2,1020a_m,1020a_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 “1020mult1” 2 (and (eq_attr “tune” “arm1020e,arm1022e”) (eq_attr “insn” “smulxy,smulwy”)) “1020a_e,1020a_m,1020a_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 “1020mult2” 2 (and (eq_attr “tune” “arm1020e,arm1022e”) (eq_attr “insn” “smlaxy,smlalxy,smlawx”)) “1020a_e*2,1020a_m,1020a_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 “1020mult3” 3 (and (eq_attr “tune” “arm1020e,arm1022e”) (eq_attr “insn” “smlalxy,mul,mla”)) “1020a_e*2,1020a_m,1020a_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 “1020mult4” 3 (and (eq_attr “tune” “arm1020e,arm1022e”) (eq_attr “insn” “muls,mlas”)) “1020a_e*4,1020a_m,1020a_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 “1020mult5” 4 (and (eq_attr “tune” “arm1020e,arm1022e”) (eq_attr “insn” “umull,umlal,smull,smlal”)) “1020a_e*3,1020a_m,1020a_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 “1020mult6” 4 (and (eq_attr “tune” “arm1020e,arm1022e”) (eq_attr “insn” “umulls,umlals,smulls,smlals”)) “1020a_e*5,1020a_m,1020a_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 “1020load1_op” 2 (and (eq_attr “tune” “arm1020e,arm1022e”) (eq_attr “type” “load_byte,load1”)) “1020a_e+1020l_e,1020l_m,1020l_w”)

(define_insn_reservation “1020store1_op” 0 (and (eq_attr “tune” “arm1020e,arm1022e”) (eq_attr “type” “store1”)) “1020a_e+1020l_e,1020l_m,1020l_w”)

;; A load's result can be stored by an immediately following store (define_bypass 1 “1020load1_op” “1020store1_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 decoupled after the first cycle unless there is ;; a register dependency; the dependency is cleared as soon as the LDM/STM ;; has dealt with the corresponding register. So for example, ;; stmia sp, {r0-r3} ;; add r0, r0, #4 ;; will have one fewer stalls than ;; stmia sp, {r0-r3} ;; add r3, r3, #4 ;; ;; As with ALU operations, if one of the destination registers is the ;; PC, there are additional stalls; that is not modeled.

(define_insn_reservation “1020load2_op” 2 (and (eq_attr “tune” “arm1020e,arm1022e”) (eq_attr “type” “load2”)) “1020a_e+1020l_e,1020l_m,1020l_w”)

(define_insn_reservation “1020store2_op” 0 (and (eq_attr “tune” “arm1020e,arm1022e”) (eq_attr “type” “store2”)) “1020a_e+1020l_e,1020l_m,1020l_w”)

(define_insn_reservation “1020load34_op” 3 (and (eq_attr “tune” “arm1020e,arm1022e”) (eq_attr “type” “load3,load4”)) “1020a_e+1020l_e,1020l_e+1020l_m,1020l_m,1020l_w”)

(define_insn_reservation “1020store34_op” 0 (and (eq_attr “tune” “arm1020e,arm1022e”) (eq_attr “type” “store3,store4”)) “1020a_e+1020l_e,1020l_e+1020l_m,1020l_m,1020l_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 “1020branch_op” 0 (and (eq_attr “tune” “arm1020e,arm1022e”) (eq_attr “type” “branch”)) “1020a_e”)

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

(define_insn_reservation “1020call_op” 32 (and (eq_attr “tune” “arm1020e,arm1022e”) (eq_attr “type” “call”)) “1020a_e*32”)

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ;; VFP ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

(define_cpu_unit “v10_fmac” “arm1020e”)

(define_cpu_unit “v10_ds” “arm1020e”)

(define_cpu_unit “v10_fmstat” “arm1020e”)

(define_cpu_unit “v10_ls1,v10_ls2,v10_ls3” “arm1020e”)

;; fmstat is a serializing instruction. It will stall the core until ;; the mac and ds units have completed. (exclusion_set “v10_fmac,v10_ds” “v10_fmstat”)

(define_attr “vfp10” “yes,no” (const (if_then_else (and (eq_attr “tune” “arm1020e,arm1022e”) (eq_attr “fpu” “vfp”)) (const_string “yes”) (const_string “no”))))

;; The VFP “type” attributes differ from those used in the FPA model. ;; ffarith Fast floating point insns, e.g. abs, neg, cpy, cmp. ;; farith Most arithmetic insns. ;; fmul Double precision multiply. ;; fdivs Single precision sqrt or division. ;; fdivd Double precision sqrt or division. ;; f_flag fmstat operation ;; f_load Floating point load from memory. ;; f_store Floating point store to memory. ;; f_2_r Transfer vfp to arm reg. ;; r_2_f Transfer arm to vfp reg.

;; Note, no instruction can issue to the VFP if the core is stalled in the ;; first execute state. We model this by using 1020a_e in the first cycle. (define_insn_reservation “v10_ffarith” 5 (and (eq_attr “vfp10” “yes”) (eq_attr “type” “ffarith”)) “1020a_e+v10_fmac”)

(define_insn_reservation “v10_farith” 5 (and (eq_attr “vfp10” “yes”) (eq_attr “type” “farith”)) “1020a_e+v10_fmac”)

(define_insn_reservation “v10_cvt” 5 (and (eq_attr “vfp10” “yes”) (eq_attr “type” “f_cvt”)) “1020a_e+v10_fmac”)

(define_insn_reservation “v10_fmul” 6 (and (eq_attr “vfp10” “yes”) (eq_attr “type” “fmul”)) “1020a_e+v10_fmac*2”)

(define_insn_reservation “v10_fdivs” 18 (and (eq_attr “vfp10” “yes”) (eq_attr “type” “fdivs”)) “1020a_e+v10_ds*14”)

(define_insn_reservation “v10_fdivd” 32 (and (eq_attr “vfp10” “yes”) (eq_attr “type” “fdivd”)) “1020a_e+v10_fmac+v10_ds*28”)

(define_insn_reservation “v10_floads” 4 (and (eq_attr “vfp10” “yes”) (eq_attr “type” “f_loads”)) “1020a_e+1020l_e+v10_ls1,v10_ls2”)

;; We model a load of a double as needing all the vfp ls* stage in cycle 1. ;; This gives the correct mix between single-and double loads where a flds ;; followed by and fldd will stall for one cycle, but two back-to-back fldd ;; insns stall for two cycles. (define_insn_reservation “v10_floadd” 5 (and (eq_attr “vfp10” “yes”) (eq_attr “type” “f_loadd”)) “1020a_e+1020l_e+v10_ls1+v10_ls2+v10_ls3,v10_ls2+v10_ls3,v10_ls3”)

;; Moves to/from arm regs also use the load/store pipeline.

(define_insn_reservation “v10_c2v” 4 (and (eq_attr “vfp10” “yes”) (eq_attr “type” “r_2_f”)) “1020a_e+1020l_e+v10_ls1,v10_ls2”)

(define_insn_reservation “v10_fstores” 1 (and (eq_attr “vfp10” “yes”) (eq_attr “type” “f_stores”)) “1020a_e+1020l_e+v10_ls1,v10_ls2”)

(define_insn_reservation “v10_fstored” 1 (and (eq_attr “vfp10” “yes”) (eq_attr “type” “f_stored”)) “1020a_e+1020l_e+v10_ls1+v10_ls2+v10_ls3,v10_ls2+v10_ls3,v10_ls3”)

(define_insn_reservation “v10_v2c” 1 (and (eq_attr “vfp10” “yes”) (eq_attr “type” “f_2_r”)) “1020a_e+1020l_e,1020l_m,1020l_w”)

(define_insn_reservation “v10_to_cpsr” 2 (and (eq_attr “vfp10” “yes”) (eq_attr “type” “f_flag”)) “1020a_e+v10_fmstat,1020a_e+1020l_e,1020l_m,1020l_w”)

;; VFP bypasses

;; There are bypasses for most operations other than store

(define_bypass 3 “v10_c2v,v10_floads” “v10_ffarith,v10_farith,v10_fmul,v10_fdivs,v10_fdivd,v10_cvt”)

(define_bypass 4 “v10_floadd” “v10_ffarith,v10_farith,v10_fmul,v10_fdivs,v10_fdivd”)

;; Arithmetic to other arithmetic saves a cycle due to forwarding (define_bypass 4 “v10_ffarith,v10_farith” “v10_ffarith,v10_farith,v10_fmul,v10_fdivs,v10_fdivd”)

(define_bypass 5 “v10_fmul” “v10_ffarith,v10_farith,v10_fmul,v10_fdivs,v10_fdivd”)

(define_bypass 17 “v10_fdivs” “v10_ffarith,v10_farith,v10_fmul,v10_fdivs,v10_fdivd”)

(define_bypass 31 “v10_fdivd” “v10_ffarith,v10_farith,v10_fmul,v10_fdivs,v10_fdivd”)

;; VFP anti-dependencies.

;; There is one anti-dependence in the following case (not yet modelled): ;; - After a store: one extra cycle for both fsts and fstd ;; Note, back-to-back fstd instructions will overload the load/store datapath ;; causing a two-cycle stall.