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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" "arith,const,logical,move,nop,shift,signext,slt"))
"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")
|
