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;;

;; Pipeline description for the VR4130 family.

;;

;; The processor issues each 8-byte aligned pair of instructions together,

;; stalling the second instruction if it depends on the first.  Thus, if we

;; want two instructions to issue in parallel, we need to make sure that the

;; first one is 8-byte aligned.

;;

;; For the purposes of this pipeline description, we treat the processor

;; like a standard two-way superscalar architecture.  If scheduling were

;; the last pass to run, we could use the scheduler hooks to vary the

;; issue rate depending on whether an instruction is at an aligned or

;; unaligned address.  Unfortunately, delayed branch scheduling and

;; hazard avoidance are done after the final scheduling pass, and they

;; can change the addresses of many instructions.

;;

;; We get around this in two ways:

;;

;;   (1) By running an extra pass at the end of compilation.  This pass goes

;;       through the function looking for pairs of instructions that could

;;       execute in parallel.  It makes sure that the first instruction in

;;       each pair is suitably aligned, inserting nops if necessary.  Doing

;;       this gives the same kind of pipeline behavior we would see on a

;;       normal superscalar target.

;;

;;       This pass is generally a speed improvement, but the extra nops will

;;       obviously make the program bigger.  It is therefore unsuitable for

;;       -Os (at the very least).

;;

;;   (2) By modifying the scheduler hooks so that, where possible:

;;

;;       (a) dependent instructions are separated by a non-dependent

;;           instruction;

;;

;;       (b) instructions that use the multiplication unit are separated

;;           by non-multiplication instructions; and

;;

;;       (c) memory access instructions are separated by non-memory

;;           instructions.

;;

;;       The idea is to keep conflicting instructions apart wherever possible

;;       and thus make the schedule less dependent on alignment.

(define_automaton "vr4130_main, vr4130_muldiv, vr4130_mulpre")

(define_cpu_unit "vr4130_alu1, vr4130_alu2, vr4130_dcache" "vr4130_main")

(define_cpu_unit "vr4130_muldiv" "vr4130_muldiv")

;; This is a fake unit for pre-reload scheduling of multiplications.

;; It enforces the true post-reload repeat rate.

(define_cpu_unit "vr4130_mulpre" "vr4130_mulpre")

;; The scheduling hooks use this attribute for (b) above.

(define_attr "vr4130_class" "mul,mem,alu"

  (cond [(eq_attr "type" "load,store")

         (const_string "mem")

         (eq_attr "type" "mfhilo,mthilo,imul,imul3,imadd,idiv")

         (const_string "mul")]

        (const_string "alu")))

(define_insn_reservation "vr4130_multi" 1

  (and (eq_attr "cpu" "r4130")

       (eq_attr "type" "multi,unknown"))

  "vr4130_alu1 + vr4130_alu2 + vr4130_dcache + vr4130_muldiv")

(define_insn_reservation "vr4130_int" 1

  (and (eq_attr "cpu" "r4130")

       (eq_attr "type" "const,arith,shift,slt,nop"))

  "vr4130_alu1 | vr4130_alu2")

(define_insn_reservation "vr4130_load" 3

  (and (eq_attr "cpu" "r4130")

       (eq_attr "type" "load"))

  "vr4130_dcache")

(define_insn_reservation "vr4130_store" 1

  (and (eq_attr "cpu" "r4130")

       (eq_attr "type" "store"))

  "vr4130_dcache")

(define_insn_reservation "vr4130_mfhilo" 3

  (and (eq_attr "cpu" "r4130")

       (eq_attr "type" "mfhilo"))

  "vr4130_muldiv")

(define_insn_reservation "vr4130_mthilo" 1

  (and (eq_attr "cpu" "r4130")

       (eq_attr "type" "mthilo"))

  "vr4130_muldiv")

;; The product is available in LO & HI after one cycle.  Moving the result

;; into an integer register will take an additional three cycles, see mflo

;; & mfhi above.  Note that the same latencies and repeat rates apply if we

;; use "mtlo; macc" instead of "mult; mflo".

(define_insn_reservation "vr4130_mulsi" 4

  (and (eq_attr "cpu" "r4130")

       (and (eq_attr "type" "imul,imul3")

            (eq_attr "mode" "SI")))

  "vr4130_muldiv + (vr4130_mulpre * 2)")

;; As for vr4130_mulsi, but the product is available in LO and HI

;; after 3 cycles.

(define_insn_reservation "vr4130_muldi" 6

  (and (eq_attr "cpu" "r4130")

       (and (eq_attr "type" "imul,imul3")

            (eq_attr "mode" "DI")))

  "(vr4130_muldiv * 3) + (vr4130_mulpre * 4)")

;; maccs can execute in consecutive cycles without stalling, but it

;; is 3 cycles before the integer destination can be read.

(define_insn_reservation "vr4130_macc" 3

  (and (eq_attr "cpu" "r4130")

       (eq_attr "type" "imadd"))

  "vr4130_muldiv")

(define_bypass 1 "vr4130_mulsi,vr4130_macc" "vr4130_macc" "mips_linked_madd_p")

(define_bypass 1 "vr4130_mulsi,vr4130_macc" "vr4130_mfhilo")

(define_bypass 3 "vr4130_muldi" "vr4130_mfhilo")

(define_insn_reservation "vr4130_divsi" 36

  (and (eq_attr "cpu" "r4130")

       (and (eq_attr "type" "idiv")

            (eq_attr "mode" "SI")))

  "vr4130_muldiv * 36")

(define_insn_reservation "vr4130_divdi" 72

  (and (eq_attr "cpu" "r4130")

       (and (eq_attr "type" "idiv")

            (eq_attr "mode" "DI")))

  "vr4130_muldiv * 72")

(define_insn_reservation "vr4130_branch" 0

  (and (eq_attr "cpu" "r4130")

       (eq_attr "type" "branch,jump,call"))

  "vr4130_alu1 | vr4130_alu2")