OV - exec - Loop 452

	Loop Id: 452	Module: exec	Source: update_halo.cpp:152-153 [...]	Coverage: 0.07%

0x42ef20 MADD	X16, X14, X4, XZR

0x42ef24 ADD	X17, X21, X16

0x42ef28 ADD	X0, X12, X16,LSL #3

0x42ef2c UBFM	X18, X16, #60, #59

0x42ef30 ADD	X5, X13, X17,LSL #3

0x42ef34 ADD	X1, X18, #8

0x42ef38 SUB	X30, X5, X0

0x42ef3c SUB	X22, X30, #8

0x42ef40 UBFM	X20, X22, #3, #63

0x42ef44 ADD	X2, X20, #1

0x42ef48 ANDS	X6, X2, #4224

0x42ef4c B.EQ	42eff8

0x42ef50 CMP	X6, #1

0x42ef54 B.EQ	42efe0

0x42ef58 CMP	X6, #2

0x42ef5c B.EQ	42efd0

0x42ef60 CMP	X6, #3

0x42ef64 B.EQ	42efc0

0x42ef68 CMP	X6, #4

0x42ef6c B.EQ	42efb0

0x42ef70 CMP	X6, #5

0x42ef74 B.EQ	42efa0

0x42ef78 CMP	X6, #6

0x42ef7c B.EQ	42ef90

0x42ef80 LDR	D0, [X0, #16]

0x42ef84 SUB	X7, X1, X0

0x42ef88 ADD	X0, X0, #8

0x42ef8c STR	D0, [X7, X3]

0x42ef90 LDR	D1, [X0, #16]

0x42ef94 SUB	X8, X1, X0

0x42ef98 ADD	X0, X0, #8

0x42ef9c STR	D1, [X8, X3]

0x42efa0 LDR	D2, [X0, #16]

0x42efa4 SUB	X9, X1, X0

0x42efa8 ADD	X0, X0, #8

0x42efac STR	D2, [X9, X3]

0x42efb0 LDR	D3, [X0, #16]

0x42efb4 SUB	X10, X1, X0

0x42efb8 ADD	X0, X0, #8

0x42efbc STR	D3, [X10, X3]

0x42efc0 LDR	D4, [X0, #16]

0x42efc4 SUB	X11, X1, X0

0x42efc8 ADD	X0, X0, #8

0x42efcc STR	D4, [X11, X3]

0x42efd0 LDR	D5, [X0, #16]

0x42efd4 SUB	X16, X1, X0

0x42efd8 ADD	X0, X0, #8

0x42efdc STR	D5, [X16, X3]

0x42efe0 LDR	D6, [X0, #16]

0x42efe4 SUB	X17, X1, X0

0x42efe8 ADD	X0, X0, #8

0x42efec STR	D6, [X17, X3]

0x42eff0 CMP	X5, X0

0x42eff4 B.EQ	42f080

  (451) 0x42eff8 LDR	D7, [X0, #16]

  (451) 0x42effc SUB	X6, X1, X0

  (451) 0x42f000 ADD	X18, X0, #8

  (451) 0x42f004 ADD	X11, X0, #16

  (451) 0x42f008 SUB	X30, X1, X18

  (451) 0x42f00c ADD	X10, X0, #24

  (451) 0x42f010 SUB	X22, X1, X11

  (451) 0x42f014 ADD	X9, X0, #32

  (451) 0x42f018 SUB	X20, X1, X10

  (451) 0x42f01c ADD	X8, X0, #40

  (451) 0x42f020 SUB	X18, X1, X9

  (451) 0x42f024 ADD	X7, X0, #48

  (451) 0x42f028 SUB	X17, X1, X8

  (451) 0x42f02c STR	D7, [X6, X3]

  (451) 0x42f030 SUB	X16, X1, X7

  (451) 0x42f034 ADD	X6, X0, #56

  (451) 0x42f038 LDR	D16, [X0, #24]

  (451) 0x42f03c SUB	X2, X1, X6

  (451) 0x42f040 ADD	X0, X0, #64

  (451) 0x42f044 STR	D16, [X30, X3]

  (451) 0x42f048 LDR	D17, [X11, #16]

  (451) 0x42f04c STR	D17, [X22, X3]

  (451) 0x42f050 LDR	D18, [X10, #16]

  (451) 0x42f054 STR	D18, [X20, X3]

  (451) 0x42f058 LDR	D19, [X9, #16]

  (451) 0x42f05c STR	D19, [X18, X3]

  (451) 0x42f060 LDR	D20, [X8, #16]

  (451) 0x42f064 STR	D20, [X17, X3]

  (451) 0x42f068 LDR	D21, [X7, #16]

  (451) 0x42f06c STR	D21, [X16, X3]

  (451) 0x42f070 LDR	D22, [X6, #16]

  (451) 0x42f074 STR	D22, [X2, X3]

  (451) 0x42f078 CMP	X5, X0

  (451) 0x42f07c B.NE	42eff8

0x42f080 ADD	X4, X4, #1

0x42f084 ADD	W5, W15, W4

0x42f088 CMP	W19, W5

0x42f08c B.GT	42ef20

/home/hbollore/qaas-runs/170-300-2310/intel/CloverLeafCXX/build/CloverLeafCXX/src/omp/context.h: 69 - 69

--------------------------------------------------------------------------------

69:   T &operator()(size_t i, size_t j) const { return data[i + j * sizeX]; }

/home/hbollore/qaas-runs/170-300-2310/intel/CloverLeafCXX/build/CloverLeafCXX/src/omp/update_halo.cpp: 152 - 153

--------------------------------------------------------------------------------

152:         for (int j = 0; j < depth; ++j) {

153:           field.energy0(1 - j, k) = field.energy0(2 + j, k);

Path /

Metric	Value
CQA speedup if no scalar integer	1.81
CQA speedup if FP arith vectorized	1.00
CQA speedup if fully vectorized	4.00
CQA speedup if no inter-iteration dependency	NA
CQA speedup if next bottleneck killed	1.21
Bottlenecks	P2, P3, P4, P5,
Function	update_halo_kernel(int, int, int, int, std::array const&, std::array const&, field_type&, int const*, int) [clone ._omp_fn.10]
Source	context.h:69-69,update_halo.cpp:152-153
Source loop unroll info	NA
Source loop unroll confidence level	NA
Unroll/vectorization loop type	NA
Unroll factor	NA
CQA cycles	8.75
CQA cycles if no scalar integer	4.83
CQA cycles if FP arith vectorized	8.75
CQA cycles if fully vectorized	2.19
Front-end cycles	7.25
DIV/SQRT cycles	4.50
P0 cycles	4.50
P1 cycles	8.75
P2 cycles	8.75
P3 cycles	8.75
P4 cycles	8.75
P5 cycles	3.50
P6 cycles	3.50
P7 cycles	0.00
P8 cycles	0.00
P9 cycles	4.83
P10 cycles	4.50
P11 cycles	4.67
P12 cycles	0.00
P13 cycles	0.00
P14 cycles	0.00
Inter-iter dependencies cycles	NA
FE+BE cycles (UFS)	NA
Stall cycles (UFS)	NA
Nb insns	58.00
Nb uops	58.00
Nb loads	NA
Nb stores	7.00
Nb stack references	0.00
FLOP/cycle	0.00
Nb FLOP add-sub	0.00
Nb FLOP mul	0.00
Nb FLOP fma	0.00
Nb FLOP div	0.00
Nb FLOP rcp	0.00
Nb FLOP sqrt	0.00
Nb FLOP rsqrt	0.00
Bytes/cycle	12.80
Bytes prefetched	0.00
Bytes loaded	56.00
Bytes stored	56.00
Stride 0	NA
Stride 1	NA
Stride n	NA
Stride unknown	NA
Stride indirect	NA
Vectorization ratio all	0.00
Vectorization ratio load	0.00
Vectorization ratio store	0.00
Vectorization ratio mul	NA
Vectorization ratio add_sub	0.00
Vectorization ratio fma	NA
Vectorization ratio div_sqrt	NA
Vectorization ratio other	0.00
Vector-efficiency ratio all	25.00
Vector-efficiency ratio load	25.00
Vector-efficiency ratio store	25.00
Vector-efficiency ratio mul	NA
Vector-efficiency ratio add_sub	25.00
Vector-efficiency ratio fma	NA
Vector-efficiency ratio div_sqrt	NA
Vector-efficiency ratio other	25.00

Metric	Value
CQA speedup if no scalar integer	1.81
CQA speedup if FP arith vectorized	1.00
CQA speedup if fully vectorized	4.00
CQA speedup if no inter-iteration dependency	NA
CQA speedup if next bottleneck killed	1.21
Bottlenecks	P2, P3, P4, P5,
Function	update_halo_kernel(int, int, int, int, std::array const&, std::array const&, field_type&, int const*, int) [clone ._omp_fn.10]
Source	context.h:69-69,update_halo.cpp:152-153
Source loop unroll info	NA
Source loop unroll confidence level	NA
Unroll/vectorization loop type	NA
Unroll factor	NA
CQA cycles	8.75
CQA cycles if no scalar integer	4.83
CQA cycles if FP arith vectorized	8.75
CQA cycles if fully vectorized	2.19
Front-end cycles	7.25
DIV/SQRT cycles	4.50
P0 cycles	4.50
P1 cycles	8.75
P2 cycles	8.75
P3 cycles	8.75
P4 cycles	8.75
P5 cycles	3.50
P6 cycles	3.50
P7 cycles	0.00
P8 cycles	0.00
P9 cycles	4.83
P10 cycles	4.50
P11 cycles	4.67
P12 cycles	0.00
P13 cycles	0.00
P14 cycles	0.00
Inter-iter dependencies cycles	NA
FE+BE cycles (UFS)	NA
Stall cycles (UFS)	NA
Nb insns	58.00
Nb uops	58.00
Nb loads	NA
Nb stores	7.00
Nb stack references	0.00
FLOP/cycle	0.00
Nb FLOP add-sub	0.00
Nb FLOP mul	0.00
Nb FLOP fma	0.00
Nb FLOP div	0.00
Nb FLOP rcp	0.00
Nb FLOP sqrt	0.00
Nb FLOP rsqrt	0.00
Bytes/cycle	12.80
Bytes prefetched	0.00
Bytes loaded	56.00
Bytes stored	56.00
Stride 0	NA
Stride 1	NA
Stride n	NA
Stride unknown	NA
Stride indirect	NA
Vectorization ratio all	0.00
Vectorization ratio load	0.00
Vectorization ratio store	0.00
Vectorization ratio mul	NA
Vectorization ratio add_sub	0.00
Vectorization ratio fma	NA
Vectorization ratio div_sqrt	NA
Vectorization ratio other	0.00
Vector-efficiency ratio all	25.00
Vector-efficiency ratio load	25.00
Vector-efficiency ratio store	25.00
Vector-efficiency ratio mul	NA
Vector-efficiency ratio add_sub	25.00
Vector-efficiency ratio fma	NA
Vector-efficiency ratio div_sqrt	NA
Vector-efficiency ratio other	25.00

Path /

Average path: Display a virtual path defined by average values of all real paths

Function	update_halo_kernel(int, int, int, int, std::array const&, std::array const&, field_type&, int const*, int) [clone ._omp_fn.10]
Source file and lines	update_halo.cpp:152-153
Module	exec

The loop is defined in:

/home/hbollore/qaas-runs/170-300-2310/intel/CloverLeafCXX/build/CloverLeafCXX/src/omp/context.h:69
/home/hbollore/qaas-runs/170-300-2310/intel/CloverLeafCXX/build/CloverLeafCXX/src/omp/update_halo.cpp:152-153

Warnings:

Non-innermost loop: analyzing only self part (ignoring child loops).
Ignoring paths for analysis
Too many paths. Rerun with max-paths=15
RecMII not computed since number of paths is unknown or > max_paths

Try to simplify control and/or increase the maximum number of paths per function/loop through the 'max-paths-nb' option.

This loop has 15 execution paths.

The presence of multiple execution paths is typically the main/first bottleneck.
Try to simplify control inside loop: ideally, try to remove all conditional expressions, for example by (if applicable):

hoisting them (moving them outside the loop)
turning them into conditional moves, MIN or MAX

Ex: if (x<0) x=0 => x = (x<0 ? 0 : x) (or MAX(0,x) after defining the corresponding macro)

gain
potential
hint
expert

Code clean check

Detected a slowdown caused by scalar integer instructions (typically used for address computation). By removing them, you can lower the cost of an iteration from 8.75 to 4.83 cycles (1.81x speedup).

Workaround

Try to reorganize arrays of structures to structures of arrays
Consider to permute loops (see vectorization gain report)

Vectorization

Your loop is not vectorized. 4 data elements could be processed at once in vector registers. By vectorizing your loop, you can lower the cost of an iteration from 8.75 to 2.19 cycles (4.00x speedup).

Details

All VPU instructions are used in scalar version (process only one data element in vector registers). Since your execution units are vector units, only a vectorized loop can use their full power.

Workaround

Try another compiler or update/tune your current one
Remove inter-iterations dependences from your loop and make it unit-stride:
- If your arrays have 2 or more dimensions, check whether elements are accessed contiguously and, otherwise, try to permute loops accordingly: C storage order is row-major: for(i) for(j) a[j][i] = b[j][i]; (slow, non stride 1) => for(i) for(j) a[i][j] = b[i][j]; (fast, stride 1)
- If your loop streams arrays of structures (AoS), try to use structures of arrays instead (SoA): for(i) a[i].x = b[i].x; (slow, non stride 1) => for(i) a.x[i] = b.x[i]; (fast, stride 1)

No data for this section

Matching between your loop (in the source code) and the binary loop

The binary loop does not contain any FP arithmetical operations. The binary loop is loading 56 bytes. The binary loop is storing 56 bytes.

General properties

nb instructions	58
loop length	232
nb stack references	0

Front-end

FIT IN UOP CACHE

front end

7.25 cycles

Back-end

	P0	P1	P2	P3	P4	P5	P6	P7	P8	P9	P10	P11	P12	P13	P14
uops	4.50	4.50	8.75	8.75	8.75	8.75	3.50	3.50	0.00	0.00	4.83	4.50	4.67	0.00	0.00
cycles	4.50	4.50	8.75	8.75	8.75	8.75	3.50	3.50	0.00	0.00	4.83	4.50	4.67	0.00	0.00

Execution ports to units layout:

P0:
P1:
P2: ALU
P3: ALU
P4: ALU
P5: ALU
P6 (128 bits): VPU, FP store data, ALU, DIV/SQRT
P7 (128 bits): VPU, ALU, FP store data
P8 (128 bits): VPU, ALU, DIV/SQRT
P9 (128 bits): ALU, VPU
P10 (256 bits): store address, load
P11 (256 bits): store address, load
P12 (256 bits): load
P13 (64 bits): store data
P14 (64 bits): store data

Cycles executing div or sqrt instructions

Cycles summary

Front-end	7.25
Overall L1	8.75

Vectorization ratios

all	0%
load	0%
store	0%
mul	NA (no mul vectorizable/vectorized instructions)
add-sub	0%
fma	NA (no fma vectorizable/vectorized instructions)
div/sqrt	NA (no div/sqrt vectorizable/vectorized instructions)
other	0%

Cycles and memory resources usage

Assuming all data fit into the L1 cache, each iteration of the binary loop takes 8.75 cycles. At this rate:

6% of peak load performance is reached (6.40 out of 96.00 bytes loaded per cycle (GB/s @ 1GHz))
13% of peak store performance is reached (6.40 out of 48.00 bytes stored per cycle (GB/s @ 1GHz))

ASM code

In the binary file, the address of the loop is: 42ef20

Instruction	Nb FU	P0	P1	P2	P3	P4	P5	P6	P7	P10	P11	P12	Latency	Recip. throughput
MADD X16, X14, X4, XZR	1	0	0	0	0	1	0	0	0	0	0	0	2	1
ADD X17, X21, X16	1	0	0	0.25	0.25	0.25	0.25	0	0	0	0	0	1	0.25
ADD X0, X12, X16,LSL #3	1	0	0	0.25	0.25	0.25	0.25	0	0	0	0	0	1	0.25
UBFM X18, X16, #60, #59	1	0	0	0.25	0.25	0.25	0.25	0	0	0	0	0	1	0.25
ADD X5, X13, X17,LSL #3	1	0	0	0.25	0.25	0.25	0.25	0	0	0	0	0	1	0.25
ADD X1, X18, #8	1	0	0	0.25	0.25	0.25	0.25	0	0	0	0	0	1	0.25
SUB X30, X5, X0	1	0	0	0.25	0.25	0.25	0.25	0	0	0	0	0	1	0.25
SUB X22, X30, #8	1	0	0	0.25	0.25	0.25	0.25	0	0	0	0	0	1	0.25
UBFM X20, X22, #3, #63	1	0	0	0.25	0.25	0.25	0.25	0	0	0	0	0	1	0.25
ADD X2, X20, #1	1	0	0	0.25	0.25	0.25	0.25	0	0	0	0	0	1	0.25
ANDS X6, X2, #4224	1	0	0	0.25	0.25	0.25	0.25	0	0	0	0	0	1	0.33
B.EQ 42eff8 <_Z18update_halo_kerneliiiiRKSt5arrayIiLm4EES2_R10field_typePKii._omp_fn.10+0x178>	1	0.50	0.50	0	0	0	0	0	0	0	0	0	1	0.50
CMP X6, #1	1	0	0	0.25	0.25	0.25	0.25	0	0	0	0	0	1	0.33
B.EQ 42efe0 <_Z18update_halo_kerneliiiiRKSt5arrayIiLm4EES2_R10field_typePKii._omp_fn.10+0x160>	1	0.50	0.50	0	0	0	0	0	0	0	0	0	1	0.50
CMP X6, #2	1	0	0	0.25	0.25	0.25	0.25	0	0	0	0	0	1	0.33
B.EQ 42efd0 <_Z18update_halo_kerneliiiiRKSt5arrayIiLm4EES2_R10field_typePKii._omp_fn.10+0x150>	1	0.50	0.50	0	0	0	0	0	0	0	0	0	1	0.50
CMP X6, #3	1	0	0	0.25	0.25	0.25	0.25	0	0	0	0	0	1	0.33
B.EQ 42efc0 <_Z18update_halo_kerneliiiiRKSt5arrayIiLm4EES2_R10field_typePKii._omp_fn.10+0x140>	1	0.50	0.50	0	0	0	0	0	0	0	0	0	1	0.50
CMP X6, #4	1	0	0	0.25	0.25	0.25	0.25	0	0	0	0	0	1	0.33
B.EQ 42efb0 <_Z18update_halo_kerneliiiiRKSt5arrayIiLm4EES2_R10field_typePKii._omp_fn.10+0x130>	1	0.50	0.50	0	0	0	0	0	0	0	0	0	1	0.50
CMP X6, #5	1	0	0	0.25	0.25	0.25	0.25	0	0	0	0	0	1	0.33
B.EQ 42efa0 <_Z18update_halo_kerneliiiiRKSt5arrayIiLm4EES2_R10field_typePKii._omp_fn.10+0x120>	1	0.50	0.50	0	0	0	0	0	0	0	0	0	1	0.50
CMP X6, #6	1	0	0	0.25	0.25	0.25	0.25	0	0	0	0	0	1	0.33
B.EQ 42ef90 <_Z18update_halo_kerneliiiiRKSt5arrayIiLm4EES2_R10field_typePKii._omp_fn.10+0x110>	1	0.50	0.50	0	0	0	0	0	0	0	0	0	1	0.50
LDR D0, [X0, #16]	1	0	0	0	0	0	0	0	0	0.33	0.33	0.33	6	0.33
SUB X7, X1, X0	1	0	0	0.25	0.25	0.25	0.25	0	0	0	0	0	1	0.25
ADD X0, X0, #8	1	0	0	0.25	0.25	0.25	0.25	0	0	0	0	0	1	0.25
STR D0, [X7, X3]	1	0	0	0	0	0	0	0.50	0.50	0.50	0.50	0	2	0.50
LDR D1, [X0, #16]	1	0	0	0	0	0	0	0	0	0.33	0.33	0.33	6	0.33
SUB X8, X1, X0	1	0	0	0.25	0.25	0.25	0.25	0	0	0	0	0	1	0.25
ADD X0, X0, #8	1	0	0	0.25	0.25	0.25	0.25	0	0	0	0	0	1	0.25
STR D1, [X8, X3]	1	0	0	0	0	0	0	0.50	0.50	0.50	0.50	0	2	0.50
LDR D2, [X0, #16]	1	0	0	0	0	0	0	0	0	0.33	0.33	0.33	6	0.33
SUB X9, X1, X0	1	0	0	0.25	0.25	0.25	0.25	0	0	0	0	0	1	0.25
ADD X0, X0, #8	1	0	0	0.25	0.25	0.25	0.25	0	0	0	0	0	1	0.25
STR D2, [X9, X3]	1	0	0	0	0	0	0	0.50	0.50	0.50	0.50	0	2	0.50
LDR D3, [X0, #16]	1	0	0	0	0	0	0	0	0	0.33	0.33	0.33	6	0.33
SUB X10, X1, X0	1	0	0	0.25	0.25	0.25	0.25	0	0	0	0	0	1	0.25
ADD X0, X0, #8	1	0	0	0.25	0.25	0.25	0.25	0	0	0	0	0	1	0.25
STR D3, [X10, X3]	1	0	0	0	0	0	0	0.50	0.50	0.50	0.50	0	2	0.50
LDR D4, [X0, #16]	1	0	0	0	0	0	0	0	0	0.33	0.33	0.33	6	0.33
SUB X11, X1, X0	1	0	0	0.25	0.25	0.25	0.25	0	0	0	0	0	1	0.25
ADD X0, X0, #8	1	0	0	0.25	0.25	0.25	0.25	0	0	0	0	0	1	0.25
STR D4, [X11, X3]	1	0	0	0	0	0	0	0.50	0.50	0.50	0.50	0	2	0.50
LDR D5, [X0, #16]	1	0	0	0	0	0	0	0	0	0.33	0.33	0.33	6	0.33
SUB X16, X1, X0	1	0	0	0.25	0.25	0.25	0.25	0	0	0	0	0	1	0.25
ADD X0, X0, #8	1	0	0	0.25	0.25	0.25	0.25	0	0	0	0	0	1	0.25
STR D5, [X16, X3]	1	0	0	0	0	0	0	0.50	0.50	0.50	0.50	0	2	0.50
LDR D6, [X0, #16]	1	0	0	0	0	0	0	0	0	0.33	0.33	0.33	6	0.33
SUB X17, X1, X0	1	0	0	0.25	0.25	0.25	0.25	0	0	0	0	0	1	0.25
ADD X0, X0, #8	1	0	0	0.25	0.25	0.25	0.25	0	0	0	0	0	1	0.25
STR D6, [X17, X3]	1	0	0	0	0	0	0	0.50	0.50	0.50	0.50	0	2	0.50
CMP X5, X0	1	0	0	0.25	0.25	0.25	0.25	0	0	0	0	0	1	0.33
B.EQ 42f080 <_Z18update_halo_kerneliiiiRKSt5arrayIiLm4EES2_R10field_typePKii._omp_fn.10+0x200>	1	0.50	0.50	0	0	0	0	0	0	0	0	0	1	0.50
ADD X4, X4, #1	1	0	0	0.25	0.25	0.25	0.25	0	0	0	0	0	1	0.25
ADD W5, W15, W4	1	0	0	0.25	0.25	0.25	0.25	0	0	0	0	0	1	0.25
CMP W19, W5	1	0	0	0.25	0.25	0.25	0.25	0	0	0	0	0	1	0.33
B.GT 42ef20 <_Z18update_halo_kerneliiiiRKSt5arrayIiLm4EES2_R10field_typePKii._omp_fn.10+0xa0>	1	0.50	0.50	0	0	0	0	0	0	0	0	0	1	0.50

Function	update_halo_kernel(int, int, int, int, std::array const&, std::array const&, field_type&, int const*, int) [clone ._omp_fn.10]
Source file and lines	update_halo.cpp:152-153
Module	exec

The loop is defined in:

/home/hbollore/qaas-runs/170-300-2310/intel/CloverLeafCXX/build/CloverLeafCXX/src/omp/context.h:69
/home/hbollore/qaas-runs/170-300-2310/intel/CloverLeafCXX/build/CloverLeafCXX/src/omp/update_halo.cpp:152-153

Warnings:

Non-innermost loop: analyzing only self part (ignoring child loops).
Ignoring paths for analysis
Too many paths. Rerun with max-paths=15
RecMII not computed since number of paths is unknown or > max_paths

hoisting them (moving them outside the loop)
turning them into conditional moves, MIN or MAX

Ex: if (x<0) x=0 => x = (x<0 ? 0 : x) (or MAX(0,x) after defining the corresponding macro)

gain
potential
hint
expert

Code clean check

Detected a slowdown caused by scalar integer instructions (typically used for address computation). By removing them, you can lower the cost of an iteration from 8.75 to 4.83 cycles (1.81x speedup).

Workaround

Try to reorganize arrays of structures to structures of arrays
Consider to permute loops (see vectorization gain report)

Vectorization

Your loop is not vectorized. 4 data elements could be processed at once in vector registers. By vectorizing your loop, you can lower the cost of an iteration from 8.75 to 2.19 cycles (4.00x speedup).

Details

All VPU instructions are used in scalar version (process only one data element in vector registers). Since your execution units are vector units, only a vectorized loop can use their full power.

Workaround

Try another compiler or update/tune your current one
Remove inter-iterations dependences from your loop and make it unit-stride:
- If your arrays have 2 or more dimensions, check whether elements are accessed contiguously and, otherwise, try to permute loops accordingly: C storage order is row-major: for(i) for(j) a[j][i] = b[j][i]; (slow, non stride 1) => for(i) for(j) a[i][j] = b[i][j]; (fast, stride 1)
- If your loop streams arrays of structures (AoS), try to use structures of arrays instead (SoA): for(i) a[i].x = b[i].x; (slow, non stride 1) => for(i) a.x[i] = b.x[i]; (fast, stride 1)

No data for this section

Matching between your loop (in the source code) and the binary loop

The binary loop does not contain any FP arithmetical operations. The binary loop is loading 56 bytes. The binary loop is storing 56 bytes.

General properties

nb instructions	58
loop length	232
nb stack references	0

Front-end

FIT IN UOP CACHE

front end

7.25 cycles

Back-end

	P0	P1	P2	P3	P4	P5	P6	P7	P8	P9	P10	P11	P12	P13	P14
uops	4.50	4.50	8.75	8.75	8.75	8.75	3.50	3.50	0.00	0.00	4.83	4.50	4.67	0.00	0.00
cycles	4.50	4.50	8.75	8.75	8.75	8.75	3.50	3.50	0.00	0.00	4.83	4.50	4.67	0.00	0.00

Execution ports to units layout:

P0:
P1:
P2: ALU
P3: ALU
P4: ALU
P5: ALU
P6 (128 bits): VPU, FP store data, ALU, DIV/SQRT
P7 (128 bits): VPU, ALU, FP store data
P8 (128 bits): VPU, ALU, DIV/SQRT
P9 (128 bits): ALU, VPU
P10 (256 bits): store address, load
P11 (256 bits): store address, load
P12 (256 bits): load
P13 (64 bits): store data
P14 (64 bits): store data

Cycles executing div or sqrt instructions

Cycles summary

Front-end	7.25
Overall L1	8.75

Vectorization ratios

all	0%
load	0%
store	0%
mul	NA (no mul vectorizable/vectorized instructions)
add-sub	0%
fma	NA (no fma vectorizable/vectorized instructions)
div/sqrt	NA (no div/sqrt vectorizable/vectorized instructions)
other	0%

Cycles and memory resources usage

Assuming all data fit into the L1 cache, each iteration of the binary loop takes 8.75 cycles. At this rate:

6% of peak load performance is reached (6.40 out of 96.00 bytes loaded per cycle (GB/s @ 1GHz))
13% of peak store performance is reached (6.40 out of 48.00 bytes stored per cycle (GB/s @ 1GHz))

ASM code

In the binary file, the address of the loop is: 42ef20

Instruction	Nb FU	P0	P1	P2	P3	P4	P5	P6	P7	P10	P11	P12	Latency	Recip. throughput
MADD X16, X14, X4, XZR	1	0	0	0	0	1	0	0	0	0	0	0	2	1
ADD X17, X21, X16	1	0	0	0.25	0.25	0.25	0.25	0	0	0	0	0	1	0.25
ADD X0, X12, X16,LSL #3	1	0	0	0.25	0.25	0.25	0.25	0	0	0	0	0	1	0.25
UBFM X18, X16, #60, #59	1	0	0	0.25	0.25	0.25	0.25	0	0	0	0	0	1	0.25
ADD X5, X13, X17,LSL #3	1	0	0	0.25	0.25	0.25	0.25	0	0	0	0	0	1	0.25
ADD X1, X18, #8	1	0	0	0.25	0.25	0.25	0.25	0	0	0	0	0	1	0.25
SUB X30, X5, X0	1	0	0	0.25	0.25	0.25	0.25	0	0	0	0	0	1	0.25
SUB X22, X30, #8	1	0	0	0.25	0.25	0.25	0.25	0	0	0	0	0	1	0.25
UBFM X20, X22, #3, #63	1	0	0	0.25	0.25	0.25	0.25	0	0	0	0	0	1	0.25
ADD X2, X20, #1	1	0	0	0.25	0.25	0.25	0.25	0	0	0	0	0	1	0.25
ANDS X6, X2, #4224	1	0	0	0.25	0.25	0.25	0.25	0	0	0	0	0	1	0.33
B.EQ 42eff8 <_Z18update_halo_kerneliiiiRKSt5arrayIiLm4EES2_R10field_typePKii._omp_fn.10+0x178>	1	0.50	0.50	0	0	0	0	0	0	0	0	0	1	0.50
CMP X6, #1	1	0	0	0.25	0.25	0.25	0.25	0	0	0	0	0	1	0.33
B.EQ 42efe0 <_Z18update_halo_kerneliiiiRKSt5arrayIiLm4EES2_R10field_typePKii._omp_fn.10+0x160>	1	0.50	0.50	0	0	0	0	0	0	0	0	0	1	0.50
CMP X6, #2	1	0	0	0.25	0.25	0.25	0.25	0	0	0	0	0	1	0.33
B.EQ 42efd0 <_Z18update_halo_kerneliiiiRKSt5arrayIiLm4EES2_R10field_typePKii._omp_fn.10+0x150>	1	0.50	0.50	0	0	0	0	0	0	0	0	0	1	0.50
CMP X6, #3	1	0	0	0.25	0.25	0.25	0.25	0	0	0	0	0	1	0.33
B.EQ 42efc0 <_Z18update_halo_kerneliiiiRKSt5arrayIiLm4EES2_R10field_typePKii._omp_fn.10+0x140>	1	0.50	0.50	0	0	0	0	0	0	0	0	0	1	0.50
CMP X6, #4	1	0	0	0.25	0.25	0.25	0.25	0	0	0	0	0	1	0.33
B.EQ 42efb0 <_Z18update_halo_kerneliiiiRKSt5arrayIiLm4EES2_R10field_typePKii._omp_fn.10+0x130>	1	0.50	0.50	0	0	0	0	0	0	0	0	0	1	0.50
CMP X6, #5	1	0	0	0.25	0.25	0.25	0.25	0	0	0	0	0	1	0.33
B.EQ 42efa0 <_Z18update_halo_kerneliiiiRKSt5arrayIiLm4EES2_R10field_typePKii._omp_fn.10+0x120>	1	0.50	0.50	0	0	0	0	0	0	0	0	0	1	0.50
CMP X6, #6	1	0	0	0.25	0.25	0.25	0.25	0	0	0	0	0	1	0.33
B.EQ 42ef90 <_Z18update_halo_kerneliiiiRKSt5arrayIiLm4EES2_R10field_typePKii._omp_fn.10+0x110>	1	0.50	0.50	0	0	0	0	0	0	0	0	0	1	0.50
LDR D0, [X0, #16]	1	0	0	0	0	0	0	0	0	0.33	0.33	0.33	6	0.33
SUB X7, X1, X0	1	0	0	0.25	0.25	0.25	0.25	0	0	0	0	0	1	0.25
ADD X0, X0, #8	1	0	0	0.25	0.25	0.25	0.25	0	0	0	0	0	1	0.25
STR D0, [X7, X3]	1	0	0	0	0	0	0	0.50	0.50	0.50	0.50	0	2	0.50
LDR D1, [X0, #16]	1	0	0	0	0	0	0	0	0	0.33	0.33	0.33	6	0.33
SUB X8, X1, X0	1	0	0	0.25	0.25	0.25	0.25	0	0	0	0	0	1	0.25
ADD X0, X0, #8	1	0	0	0.25	0.25	0.25	0.25	0	0	0	0	0	1	0.25
STR D1, [X8, X3]	1	0	0	0	0	0	0	0.50	0.50	0.50	0.50	0	2	0.50
LDR D2, [X0, #16]	1	0	0	0	0	0	0	0	0	0.33	0.33	0.33	6	0.33
SUB X9, X1, X0	1	0	0	0.25	0.25	0.25	0.25	0	0	0	0	0	1	0.25
ADD X0, X0, #8	1	0	0	0.25	0.25	0.25	0.25	0	0	0	0	0	1	0.25
STR D2, [X9, X3]	1	0	0	0	0	0	0	0.50	0.50	0.50	0.50	0	2	0.50
LDR D3, [X0, #16]	1	0	0	0	0	0	0	0	0	0.33	0.33	0.33	6	0.33
SUB X10, X1, X0	1	0	0	0.25	0.25	0.25	0.25	0	0	0	0	0	1	0.25
ADD X0, X0, #8	1	0	0	0.25	0.25	0.25	0.25	0	0	0	0	0	1	0.25
STR D3, [X10, X3]	1	0	0	0	0	0	0	0.50	0.50	0.50	0.50	0	2	0.50
LDR D4, [X0, #16]	1	0	0	0	0	0	0	0	0	0.33	0.33	0.33	6	0.33
SUB X11, X1, X0	1	0	0	0.25	0.25	0.25	0.25	0	0	0	0	0	1	0.25
ADD X0, X0, #8	1	0	0	0.25	0.25	0.25	0.25	0	0	0	0	0	1	0.25
STR D4, [X11, X3]	1	0	0	0	0	0	0	0.50	0.50	0.50	0.50	0	2	0.50
LDR D5, [X0, #16]	1	0	0	0	0	0	0	0	0	0.33	0.33	0.33	6	0.33
SUB X16, X1, X0	1	0	0	0.25	0.25	0.25	0.25	0	0	0	0	0	1	0.25
ADD X0, X0, #8	1	0	0	0.25	0.25	0.25	0.25	0	0	0	0	0	1	0.25
STR D5, [X16, X3]	1	0	0	0	0	0	0	0.50	0.50	0.50	0.50	0	2	0.50
LDR D6, [X0, #16]	1	0	0	0	0	0	0	0	0	0.33	0.33	0.33	6	0.33
SUB X17, X1, X0	1	0	0	0.25	0.25	0.25	0.25	0	0	0	0	0	1	0.25
ADD X0, X0, #8	1	0	0	0.25	0.25	0.25	0.25	0	0	0	0	0	1	0.25
STR D6, [X17, X3]	1	0	0	0	0	0	0	0.50	0.50	0.50	0.50	0	2	0.50
CMP X5, X0	1	0	0	0.25	0.25	0.25	0.25	0	0	0	0	0	1	0.33
B.EQ 42f080 <_Z18update_halo_kerneliiiiRKSt5arrayIiLm4EES2_R10field_typePKii._omp_fn.10+0x200>	1	0.50	0.50	0	0	0	0	0	0	0	0	0	1	0.50
ADD X4, X4, #1	1	0	0	0.25	0.25	0.25	0.25	0	0	0	0	0	1	0.25
ADD W5, W15, W4	1	0	0	0.25	0.25	0.25	0.25	0	0	0	0	0	1	0.25
CMP W19, W5	1	0	0	0.25	0.25	0.25	0.25	0	0	0	0	0	1	0.33
B.GT 42ef20 <_Z18update_halo_kerneliiiiRKSt5arrayIiLm4EES2_R10field_typePKii._omp_fn.10+0xa0>	1	0.50	0.50	0	0	0	0	0	0	0	0	0	1	0.50

Report Configuration

Code clean check

Workaround

Vectorization

Details

Workaround

Matching between your loop (in the source code) and the binary loop

General properties

Front-end

Back-end

Cycles summary

Vectorization ratios

Cycles and memory resources usage

ASM code

Code clean check

Workaround

Vectorization

Details

Workaround

Matching between your loop (in the source code) and the binary loop

General properties

Front-end

Back-end

Cycles summary

Vectorization ratios

Cycles and memory resources usage

ASM code