Apple Microarchitecture Research by Dougall Johnson

M1/A14 P-core (Firestorm): Overview | Base Instructions | SIMD and FP Instructions
M1/A14 E-core (Icestorm):  Overview | Base Instructions | SIMD and FP Instructions

LDRH

Test 1: uops

Code:

  ldrh w0, [x6]

Initialization

  mov x0, 1
  mov x1, 2
  mov x8, 0

(no loop instructions)

1000 unrolls and 1 iteration

Retires: 1.000

Issues: 1.000

Integer unit issues: 0.001

Load/store unit issues: 1.000

SIMD/FP unit issues: 0.000

Recorded non-zero counters (first 10 of 64 runs)

retire uop (01)	cycle (02)	schedule uop (52)	schedule int uop (53)	schedule ldst uop (55)	dispatch ldst uop (58)	simd uops in schedulers (5a)	dispatch uop (78)	map ldst uop (7d)	map ldst uop inputs (80)	? int output thing (e9)	? ldst retires (ed)
1005	651	1027	1	1026	1000	8238	1000	1000	1000	1	1000
1004	554	1001	1	1000	1000	8112	1000	1000	1000	1	1000
1004	547	1001	1	1000	1000	8112	1000	1000	1000	1	1000
1004	547	1001	1	1000	1000	8112	1000	1000	1000	1	1000
1004	547	1001	1	1000	1000	8112	1000	1000	1000	1	1000
1004	547	1001	1	1000	1000	8112	1000	1000	1000	1	1000
1004	547	1001	1	1000	1000	8112	1000	1000	1000	1	1000
1004	547	1001	1	1000	1000	8112	1000	1000	1000	1	1000
1004	547	1001	1	1000	1000	8112	1000	1000	1000	1	1000
1004	547	1001	1	1000	1000	8112	1000	1000	1000	1	1000

Test 2: Latency 1->2 (with chain penalty)

Chain cycles: 3

Code:

  ldrh w0, [x6]
  eor x8, x8, x0
  eor x8, x8, x0
  add x6, x6, x8

Initialization

  mov x0, 1
  mov x1, 2
  mov x8, 0

(fused SUBS/B.cc loop)

100 unrolls and 100 iterations

Result (median cycles for code, minus 3 chain cycles): 4.0042

Recorded non-zero counters (first 10 of 64 runs)

retire uop (01)	cycle (02)	schedule uop (52)	schedule int uop (53)	schedule ldst uop (55)	dispatch int uop (56)	dispatch ldst uop (58)	int uops in schedulers (59)	simd uops in schedulers (5a)	dispatch uop (78)	map int uop (7c)	map ldst uop (7d)	map int uop inputs (7f)	map ldst uop inputs (80)	? int output thing (e9)	? ldst retires (ed)	? int retires (ef)
40206	70179	40116	30113	10003	30162	10003	1859398	693968	40106	30212	10004	60224	10004	30002	10000	30100
40204	70042	40102	30102	10000	30103	10003	1859446	694013	40106	30212	10004	60224	10004	30002	10000	30100
40204	70042	40102	30102	10000	30103	10003	1859446	694013	40106	30212	10004	60224	10004	30002	10000	30100
40204	70042	40102	30102	10000	30103	10003	1859446	694013	40106	30212	10004	60224	10004	30002	10000	30100
40204	70042	40102	30102	10000	30103	10003	1859446	694013	40106	30212	10004	60224	10004	30002	10000	30100
40204	70042	40102	30102	10000	30103	10003	1859446	694013	40106	30212	10004	60224	10004	30002	10000	30100
40204	70042	40102	30102	10000	30103	10003	1859446	694013	40106	30212	10004	60224	10004	30002	10000	30100
40204	70042	40102	30102	10000	30103	10003	1859446	694013	40106	30212	10004	60224	10004	30002	10000	30100
40204	70158	40103	30103	10000	30103	10015	1864192	695901	40150	30247	10017	60224	10004	30002	10000	30100
40204	70046	40102	30102	10000	30103	10003	1859446	694013	40106	30212	10004	60224	10004	30002	10000	30100

1000 unrolls and 10 iterations

Result (median cycles for code, minus 3 chain cycles): 4.0047

Recorded non-zero counters (first 10 of 64 runs)

retire uop (01)	cycle (02)	schedule uop (52)	schedule int uop (53)	schedule ldst uop (55)	dispatch int uop (56)	dispatch ldst uop (58)	int uops in schedulers (59)	simd uops in schedulers (5a)	dispatch uop (78)	map int uop (7c)	map ldst uop (7d)	map int uop inputs (7f)	map ldst uop inputs (80)	? int output thing (e9)	? ldst retires (ed)	? int retires (ef)
40025	70149	40018	30017	10001	30040	10000	1859604	694669	40010	30020	10000	60020	10000	30003	10000	30010
40025	70077	40021	30019	10002	30045	10000	1859604	694669	40010	30020	10000	60020	10000	30003	10000	30010
40025	70136	40024	30022	10002	30045	10000	1859733	694744	40010	30020	10000	60020	10000	30003	10000	30010
40024	70047	40013	30013	10000	30010	10000	1859652	694714	40010	30020	10000	60020	10000	30003	10000	30010
40024	70047	40013	30013	10000	30010	10000	1859652	694714	40010	30020	10000	60020	10000	30003	10000	30010
40024	70047	40013	30013	10000	30010	10000	1859652	694714	40010	30020	10000	60020	10000	30003	10000	30010
40024	70047	40013	30013	10000	30010	10000	1859652	694714	40010	30020	10000	60020	10000	30003	10000	30010
40024	70047	40013	30013	10000	30010	10000	1859652	694714	40010	30020	10000	60020	10000	30003	10000	30010
40024	70047	40013	30013	10000	30010	10000	1859652	694714	40010	30020	10000	60020	10000	30003	10000	30010
40024	70047	40013	30013	10000	30010	10000	1859652	694714	40010	30020	10000	60020	10000	30003	10000	30010

Test 3: throughput

Count: 8

Code:

  ldrh w0, [x6]
  ldrh w0, [x6]
  ldrh w0, [x6]
  ldrh w0, [x6]
  ldrh w0, [x6]
  ldrh w0, [x6]
  ldrh w0, [x6]
  ldrh w0, [x6]

Initialization

  mov x7, x6
  mov x8, x6
  mov x9, x6
  mov x10, x6
  mov x11, x6
  mov x12, x6
  mov x13, x6

(fused SUBS/B.cc loop)

100 unrolls and 100 iterations

Result (median cycles for code divided by count): 0.5006

Recorded non-zero counters (first 10 of 64 runs)

retire uop (01)	cycle (02)	schedule uop (52)	schedule int uop (53)	schedule ldst uop (55)	dispatch int uop (56)	dispatch ldst uop (58)	int uops in schedulers (59)	simd uops in schedulers (5a)	dispatch uop (78)	map int uop (7c)	map ldst uop (7d)	map int uop inputs (7f)	map ldst uop inputs (80)	? int output thing (e9)	? ldst retires (ed)	? int retires (ef)
80205	43249	80135	101	80034	100	80008	300	256190	80108	200	80012	200	80012	1	80000	100
80204	40045	80101	101	80000	100	80008	300	640196	80108	200	80012	200	80012	1	80000	100
80204	40045	80101	101	80000	100	80008	300	640196	80108	200	80012	200	80012	1	80000	100
80204	40045	80101	101	80000	100	80008	300	640196	80108	200	80012	200	80012	1	80000	100
80204	40045	80101	101	80000	100	80008	300	640196	80108	200	80012	200	80012	1	80000	100
80204	40045	80101	101	80000	100	80008	300	640196	80108	200	80012	200	80012	1	80000	100
80204	40045	80101	101	80000	100	80008	300	640196	80108	200	80012	200	80012	1	80000	100
80204	40045	80101	101	80000	100	80056	300	537030	80156	200	80069	200	80012	1	80000	100
80204	40045	80101	101	80000	100	80008	300	640196	80108	200	80012	200	80012	1	80000	100
80204	40045	80101	101	80000	100	80008	300	640196	80108	200	80012	200	80012	1	80000	100

1000 unrolls and 10 iterations

Result (median cycles for code divided by count): 0.5005

Recorded non-zero counters (first 10 of 64 runs)

retire uop (01)	cycle (02)	schedule uop (52)	schedule int uop (53)	schedule ldst uop (55)	dispatch int uop (56)	dispatch ldst uop (58)	int uops in schedulers (59)	simd uops in schedulers (5a)	dispatch uop (78)	map int uop (7c)	map ldst uop (7d)	map int uop inputs (7f)	map ldst uop inputs (80)	? int output thing (e9)	? ldst retires (ed)	? int retires (ef)
80024	40057	80015	11	80004	10	80000	30	640040	80010	20	80000	20	80000	1	80000	10
80024	40043	80011	11	80000	10	80000	30	640040	80010	20	80000	20	80000	1	80000	10
80024	40043	80011	11	80000	10	80000	30	640040	80010	20	80000	20	80000	1	80000	10
80024	40043	80011	11	80000	10	80000	30	640040	80010	20	80000	20	80000	1	80000	10
80024	40043	80011	11	80000	10	80000	30	640040	80010	20	80000	20	80000	1	80000	10
80024	40053	80011	11	80000	10	80000	30	640490	80010	20	80000	20	80000	1	80000	10
80024	40046	80011	11	80000	10	80000	30	640040	80010	20	80000	20	80000	1	80000	10
80024	40043	80011	11	80000	10	80000	30	640040	80010	20	80000	20	80000	1	80000	10
80024	40043	80011	11	80000	10	80000	30	640040	80010	20	80000	20	80000	1	80000	10
80024	40043	80011	11	80000	10	80000	30	640040	80010	20	80000	20	80000	1	80000	10