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

LDRSB (32-bit)

Test 1: uops

Code:

  ldrsb 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	663	1025	1	1024	1000	8238	1000	1000	1000	1	1000
1004	554	1001	1	1000	1000	8238	1000	1000	1000	1	1000
1004	554	1001	1	1000	1000	8238	1000	1000	1000	1	1000
1004	554	1001	1	1000	1000	8238	1000	1000	1000	1	1000
1004	554	1001	1	1000	1000	8238	1000	1000	1000	1	1000
1004	554	1001	1	1000	1000	8238	1000	1000	1000	1	1000
1004	554	1001	1	1000	1000	8238	1000	1000	1000	1	1000
1004	554	1001	1	1000	1000	8238	1000	1000	1000	1	1000
1004	554	1001	1	1000	1000	8238	1000	1000	1000	1	1000
1004	554	1001	1	1000	1000	8238	1000	1000	1000	1	1000

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

Chain cycles: 3

Code:

  ldrsb 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): 4.0049

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	70180	40116	30113	10003	30162	10003	1859587	694038	40106	30212	10004	60224	10004	30003	10000	30100
40204	70049	40103	30103	10000	30103	10003	1859635	694083	40106	30212	10004	60224	10004	30003	10000	30100
40204	70049	40103	30103	10000	30103	10003	1859635	694083	40106	30212	10004	60224	10004	30003	10000	30100
40204	70049	40103	30103	10000	30103	10003	1859635	694083	40106	30212	10004	60224	10004	30003	10000	30100
40204	70049	40103	30103	10000	30103	10003	1859635	694083	40106	30212	10004	60224	10004	30003	10000	30100
40204	70049	40103	30103	10000	30103	10003	1859635	694083	40106	30212	10004	60224	10004	30003	10000	30100
40204	70049	40103	30103	10000	30103	10003	1859635	694083	40106	30212	10004	60224	10004	30003	10000	30100
40204	70049	40103	30103	10000	30103	10003	1859635	694083	40106	30212	10004	60224	10004	30003	10000	30100
40205	70086	40111	30109	10002	30135	10003	1859662	694094	40106	30212	10004	60224	10004	30003	10000	30100
40204	70049	40103	30103	10000	30103	10003	1859635	694083	40106	30212	10004	60224	10004	30003	10000	30100

1000 unrolls and 10 iterations

Result (median cycles for code, minus 3 chain cycles): 4.0040

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	70153	40018	30017	10001	30040	10003	1859671	694738	40016	30032	10004	60020	10000	30003	10000	30010
40024	70047	40013	30013	10000	30010	10000	1859463	694644	40010	30020	10000	60020	10000	30002	10000	30010
40024	70040	40012	30012	10000	30010	10000	1861785	695590	40010	30020	10000	60020	10000	30002	10000	30010
40024	70040	40012	30012	10000	30010	10000	1859463	694644	40010	30020	10000	60020	10000	30002	10000	30010
40024	70040	40012	30012	10000	30010	10000	1859463	694644	40010	30020	10000	60020	10000	30002	10000	30010
40024	70051	40012	30012	10000	30010	10000	1859625	694710	40010	30020	10000	60020	10000	30002	10000	30010
40024	70040	40012	30012	10000	30010	10000	1859463	694644	40010	30020	10000	60020	10000	30002	10000	30010
40024	70040	40012	30012	10000	30010	10000	1859463	694644	40010	30020	10000	60020	10000	30002	10000	30010
40024	70040	40012	30012	10000	30010	10000	1859463	694644	40010	30020	10000	60020	10000	30002	10000	30010
40024	70040	40012	30012	10000	30010	10000	1859463	694644	40010	30020	10000	60020	10000	30002	10000	30010

Test 3: throughput

Count: 8

Code:

  ldrsb w0, [x6]
  ldrsb w0, [x6]
  ldrsb w0, [x6]
  ldrsb w0, [x6]
  ldrsb w0, [x6]
  ldrsb w0, [x6]
  ldrsb w0, [x6]
  ldrsb 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	43751	80135	101	80034	100	80008	300	336190	80108	200	80012	200	80012	1	80000	100
80204	40052	80101	101	80000	100	80008	300	640070	80108	200	80012	200	80012	1	80000	100
80204	40045	80101	101	80000	100	80008	300	640070	80108	200	80012	200	80012	1	80000	100
80204	40045	80101	101	80000	100	80008	300	640070	80108	200	80012	200	80012	1	80000	100
80204	40045	80101	101	80000	100	80008	300	640070	80108	200	80012	200	80012	1	80000	100
80204	40045	80101	101	80000	100	80008	300	640070	80108	200	80012	200	80012	1	80000	100
80204	40045	80101	101	80000	100	80008	300	640070	80108	200	80012	200	80012	1	80000	100
80204	40045	80101	101	80000	100	80008	300	640070	80108	200	80012	200	80012	1	80000	100
80204	40045	80101	101	80000	100	80008	300	640070	80108	200	80012	200	80012	1	80000	100
80204	40045	80101	101	80000	100	80008	300	640070	80108	200	80012	200	80012	1	80000	100

1000 unrolls and 10 iterations

Result (median cycles for code divided by count): 0.5007

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)
80025	40280	80037	11	80026	10	80000	30	640238	80010	20	80000	20	80000	1	80000	10
80024	40047	80011	11	80000	10	80000	30	640238	80010	20	80000	20	80000	1	80000	10
80024	40059	80011	11	80000	10	80000	30	640382	80010	20	80000	20	80171	1	80000	10
80024	40093	80011	11	80000	10	80000	30	640238	80010	20	80000	20	80000	1	80000	10
80024	40054	80011	11	80000	10	80000	30	640238	80010	20	80000	20	80000	1	80000	10
80025	40110	80048	11	80037	10	80000	30	640112	80010	20	80000	20	80000	1	80000	10
80025	40136	80042	11	80031	10	80000	30	640112	80010	20	80000	20	80000	1	80000	10
80024	40054	80011	11	80000	10	80000	30	640238	80010	20	80000	20	80000	1	80000	10
80024	40528	80131	11	80120	10	80000	30	640922	80010	20	80000	20	80000	1	80000	10
80024	40054	80011	11	80000	10	80000	30	641570	80010	20	80000	20	80000	1	80000	10