OV - attention-clang-znver5-256 - Loop 84 - attention-clang-znver5-256

	Loop Id: 84	Module: attention-clang-znver5-256	Source: attention_v2.cpp:26-33	Coverage: 0.45%

0x4e40 MOV	0x120(%RSP),%RAX

0x4e48 MOV	0x68(%RSP),%RDX

0x4e4d VCVTSD2SS	%XMM0,%XMM0,%XMM0

0x4e51 LEA	(%RAX,%RSI,1),%R9D

0x4e55 INC	%RSI

0x4e58 VMOVSS	%XMM0,(%RDX,%R9,4)

0x4e5e MOV	0x28(%RSP),%R9

0x4e63 CMP	%R9,%RSI

0x4e66 JE	4df0

0x4e68 CMP	$0x3,%R9D

0x4e6c JBE	4e8b

0x4e6e MOV	%ESI,%R9D

0x4e71 ADD	0x98(%RSP),%R9D

0x4e79 SETB	%R9B

0x4e7d OR	0xa0(%RSP),%R9B

0x4e85 JE	71e9

0x4e8b CMPQ	$0x7,0x98(%RSP)

0x4e94 VXORPS	%XMM0,%XMM0,%XMM0

0x4e98 MOV	%RSI,0x140(%RSP)

0x4ea0 JAE	4ec0

0x4ea2 MOV	0x60(%RSP),%R14

0x4ea7 MOV	0x48(%RSP),%R8

0x4eac XOR	%R9D,%R9D

0x4eaf JMP	5044

0x4ec0 MOV	%RSI,%R10

0x4ec3 MOV	0x248(%RSP),%RAX

0x4ecb MOV	0x2c8(%RSP),%RDI

0x4ed3 MOV	0x2c0(%RSP),%RSI

0x4edb MOV	0x2b8(%RSP),%R12

0x4ee3 MOV	0x2b0(%RSP),%R13

0x4eeb MOV	0x2a8(%RSP),%R15

0x4ef3 MOV	0x60(%RSP),%R14

0x4ef8 MOV	0x48(%RSP),%R8

0x4efd MOV	0x2a0(%RSP),%RDX

0x4f05 XOR	%R9D,%R9D

0x4f08 NOPL	(%RAX,%RAX,1)

  (41) 0x4f10 LEA	(%RCX,%R9,1),%R11D

  (41) 0x4f14 VMOVSS	(%R8,%R11,4),%XMM1

  (41) 0x4f1a MOV	%R10D,%R11D

  (41) 0x4f1d VMOVSS	(%R14,%R11,4),%XMM2

  (41) 0x4f23 LEA	0x1(%RCX,%R9,1),%R11D

  (41) 0x4f28 VMOVSS	(%R8,%R11,4),%XMM3

  (41) 0x4f2e LEA	(%RBX,%R10,1),%R11D

  (41) 0x4f32 LEA	0x6(%RCX,%R9,1),%EBX

  (41) 0x4f37 VMOVSS	(%R14,%R11,4),%XMM4

  (41) 0x4f3d LEA	0x2(%RCX,%R9,1),%R11D

  (41) 0x4f42 VMOVSS	(%R8,%RBX,4),%XMM13

  (41) 0x4f48 MOV	0x38(%RSP),%RBX

  (41) 0x4f4d VMOVSS	(%R8,%R11,4),%XMM5

  (41) 0x4f53 LEA	(%RSI,%R10,1),%R11D

  (41) 0x4f57 VMOVSS	(%R14,%R11,4),%XMM6

  (41) 0x4f5d LEA	0x3(%RCX,%R9,1),%R11D

  (41) 0x4f62 VCVTSS2SD	%XMM1,%XMM1,%XMM1

  (41) 0x4f66 VCVTSS2SD	%XMM2,%XMM2,%XMM2

  (41) 0x4f6a VMOVSS	(%R8,%R11,4),%XMM7

  (41) 0x4f70 LEA	(%RDX,%R10,1),%R11D

  (41) 0x4f74 VMOVSS	(%R14,%R11,4),%XMM8

  (41) 0x4f7a LEA	0x4(%RCX,%R9,1),%R11D

  (41) 0x4f7f VFMADD213SD	%XMM0,%XMM1,%XMM2

  (41) 0x4f84 VCVTSS2SD	%XMM3,%XMM3,%XMM0

  (41) 0x4f88 VMOVSS	(%R8,%R11,4),%XMM9

  (41) 0x4f8e LEA	(%R15,%R10,1),%R11D

  (41) 0x4f92 VMOVSS	(%R14,%R11,4),%XMM10

  (41) 0x4f98 LEA	0x5(%RCX,%R9,1),%R11D

  (41) 0x4f9d VCVTSS2SD	%XMM4,%XMM4,%XMM1

  (41) 0x4fa1 VMOVSS	(%R8,%R11,4),%XMM11

  (41) 0x4fa7 LEA	(%R13,%R10,1),%R11D

  (41) 0x4fac VMOVSS	(%R14,%R11,4),%XMM12

  (41) 0x4fb2 LEA	(%R12,%R10,1),%R11D

  (41) 0x4fb6 VMOVSS	(%R14,%R11,4),%XMM14

  (41) 0x4fbc LEA	0x7(%RCX,%R9,1),%R11D

  (41) 0x4fc1 ADD	$0x8,%R9

  (41) 0x4fc5 VFMADD213SD	%XMM2,%XMM0,%XMM1

  (41) 0x4fca VCVTSS2SD	%XMM5,%XMM5,%XMM0

  (41) 0x4fce VMOVSS	(%R8,%R11,4),%XMM15

  (41) 0x4fd4 LEA	(%RDI,%R10,1),%R11D

  (41) 0x4fd8 ADD	%RAX,%R10

  (41) 0x4fdb VMOVSS	(%R14,%R11,4),%XMM16

  (41) 0x4fe2 VCVTSS2SD	%XMM6,%XMM6,%XMM2

  (41) 0x4fe6 VFMADD213SD	%XMM1,%XMM0,%XMM2

  (41) 0x4feb VCVTSS2SD	%XMM7,%XMM7,%XMM0

  (41) 0x4fef VCVTSS2SD	%XMM8,%XMM8,%XMM1

  (41) 0x4ff4 VFMADD213SD	%XMM2,%XMM0,%XMM1

  (41) 0x4ff9 VCVTSS2SD	%XMM9,%XMM9,%XMM0

  (41) 0x4ffe VCVTSS2SD	%XMM10,%XMM10,%XMM2

  (41) 0x5003 VFMADD213SD	%XMM1,%XMM0,%XMM2

  (41) 0x5008 VCVTSS2SD	%XMM11,%XMM11,%XMM0

  (41) 0x500d VCVTSS2SD	%XMM12,%XMM12,%XMM1

  (41) 0x5012 VFMADD213SD	%XMM2,%XMM0,%XMM1

  (41) 0x5017 VCVTSS2SD	%XMM13,%XMM13,%XMM0

  (41) 0x501c VCVTSS2SD	%XMM14,%XMM14,%XMM2

  (41) 0x5021 VFMADD213SD	%XMM1,%XMM0,%XMM2

  (41) 0x5026 VCVTSS2SD	%XMM15,%XMM15,%XMM1

  (41) 0x502b VCVTSS2SD	%XMM16,%XMM16,%XMM0

  (41) 0x5031 VFMADD213SD	%XMM2,%XMM1,%XMM0

  (41) 0x5036 CMP	%R9,0x1c0(%RSP)

  (41) 0x503e JNE	4f10

0x5044 CMPQ	$0,0x250(%RSP)

0x504d MOV	0x140(%RSP),%RSI

0x5055 JE	4e40

0x505b MOV	0x250(%RSP),%R11

0x5063 MOV	%RBX,%R10

0x5066 IMUL	%R9,%R10

0x506a ADD	%ECX,%R9D

0x506d ADD	%RSI,%R10

  (85) 0x5070 MOV	%R9D,%EBX

  (85) 0x5073 VMOVSS	(%R8,%RBX,4),%XMM1

  (85) 0x5079 MOV	%R10D,%EBX

  (85) 0x507c VMOVSS	(%R14,%RBX,4),%XMM2

  (85) 0x5082 MOV	0x38(%RSP),%RBX

  (85) 0x5087 INC	%R9D

  (85) 0x508a ADD	%RBX,%R10

  (85) 0x508d DEC	%R11

  (85) 0x5090 VCVTSS2SD	%XMM1,%XMM1,%XMM1

  (85) 0x5094 VCVTSS2SD	%XMM2,%XMM2,%XMM2

  (85) 0x5098 VFMADD231SD	%XMM2,%XMM1,%XMM0

  (85) 0x509d JNE	5070

0x509f JMP	4e40

/home/eoseret/llm-attention/attention_v2.cpp: 26 - 33

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

26:    for (unsigned int i = 0; i < M; ++i) {

27:       for (unsigned int j = 0; j < N; ++j) {  //vectorized

28:          double sum = 0.0;

29: #pragma clang loop vectorize(enable)

30:          for (unsigned int k = 0; k < K; ++k) { //vectorized

31:             sum += (double)A[i * K + k] * (double)B[k * N + j];

32:          }

33:          C[i * N + j] = alpha * static_cast<float>(sum);

Coverage (%)	Name	Source Location	Module

min	med	avg	max

Percentile Index	10	20	30	40	50	60	70	80	90	100
Value

min	med	avg	max

Percentile Index	10	20	30	40	50	60	70	80	90	100
Value

Path /

Metric	Value
CQA speedup if no scalar integer	2.93
CQA speedup if FP arith vectorized	1.00
CQA speedup if fully vectorized	10.35
CQA speedup if no inter-iteration dependency	NA
CQA speedup if next bottleneck killed	1.83
Bottlenecks	micro-operation queue, P6, P7, P8, P9,
Function	main
Source	attention_v2.cpp:26-27,attention_v2.cpp:30-30,attention_v2.cpp:33-33
Source loop unroll info	NA
Source loop unroll confidence level	NA
Unroll/vectorization loop type	NA
Unroll factor	NA
CQA cycles	5.50
CQA cycles if no scalar integer	1.88
CQA cycles if FP arith vectorized	5.50
CQA cycles if fully vectorized	0.53
Front-end cycles	5.50
P0 cycles	3.00
P1 cycles	3.00
P2 cycles	3.00
P3 cycles	3.00
P4 cycles	3.00
P5 cycles	3.00
P6 cycles	5.50
P7 cycles	5.50
P8 cycles	5.50
P9 cycles	5.50
P10 cycles	0.00
P11 cycles	0.00
P12 cycles	0.50
P13 cycles	0.50
P14 cycles	0.50
P15 cycles	0.50
DIV/SQRT cycles	0.00
Inter-iter dependencies cycles	NA
FE+BE cycles (UFS)	NA
Stall cycles (UFS)	NA
Nb insns	45.00
Nb uops	44.00
Nb loads	20.00
Nb stores	2.00
Nb stack references	16.00
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	29.27
Bytes prefetched	0.00
Bytes loaded	149.00
Bytes stored	12.00
Stride 0	NA
Stride 1	NA
Stride n	NA
Stride unknown	NA
Stride indirect	NA
Vectorization ratio all	5.88
Vectorization ratio load	0.00
Vectorization ratio store	0.00
Vectorization ratio mul	NA
Vectorization ratio add_sub	NA
Vectorization ratio fma	NA
Vectorization ratio div_sqrt	NA
Vectorization ratio other	16.67
Vector-efficiency ratio all	12.50
Vector-efficiency ratio load	12.50
Vector-efficiency ratio store	9.38
Vector-efficiency ratio mul	NA
Vector-efficiency ratio add_sub	NA
Vector-efficiency ratio fma	NA
Vector-efficiency ratio div_sqrt	NA
Vector-efficiency ratio other	13.54

Metric	Value
CQA speedup if no scalar integer	2.93
CQA speedup if FP arith vectorized	1.00
CQA speedup if fully vectorized	10.35
CQA speedup if no inter-iteration dependency	NA
CQA speedup if next bottleneck killed	1.83
Bottlenecks	micro-operation queue, P6, P7, P8, P9,
Function	main
Source	attention_v2.cpp:26-27,attention_v2.cpp:30-30,attention_v2.cpp:33-33
Source loop unroll info	NA
Source loop unroll confidence level	NA
Unroll/vectorization loop type	NA
Unroll factor	NA
CQA cycles	5.50
CQA cycles if no scalar integer	1.88
CQA cycles if FP arith vectorized	5.50
CQA cycles if fully vectorized	0.53
Front-end cycles	5.50
P0 cycles	3.00
P1 cycles	3.00
P2 cycles	3.00
P3 cycles	3.00
P4 cycles	3.00
P5 cycles	3.00
P6 cycles	5.50
P7 cycles	5.50
P8 cycles	5.50
P9 cycles	5.50
P10 cycles	0.00
P11 cycles	0.00
P12 cycles	0.50
P13 cycles	0.50
P14 cycles	0.50
P15 cycles	0.50
DIV/SQRT cycles	0.00
Inter-iter dependencies cycles	NA
FE+BE cycles (UFS)	NA
Stall cycles (UFS)	NA
Nb insns	45.00
Nb uops	44.00
Nb loads	20.00
Nb stores	2.00
Nb stack references	16.00
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	29.27
Bytes prefetched	0.00
Bytes loaded	149.00
Bytes stored	12.00
Stride 0	NA
Stride 1	NA
Stride n	NA
Stride unknown	NA
Stride indirect	NA
Vectorization ratio all	5.88
Vectorization ratio load	0.00
Vectorization ratio store	0.00
Vectorization ratio mul	NA
Vectorization ratio add_sub	NA
Vectorization ratio fma	NA
Vectorization ratio div_sqrt	NA
Vectorization ratio other	16.67
Vector-efficiency ratio all	12.50
Vector-efficiency ratio load	12.50
Vector-efficiency ratio store	9.38
Vector-efficiency ratio mul	NA
Vector-efficiency ratio add_sub	NA
Vector-efficiency ratio fma	NA
Vector-efficiency ratio div_sqrt	NA
Vector-efficiency ratio other	13.54

Path /

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

Function	main
Source file and lines	attention_v2.cpp:26-33
Module	attention-clang-znver5-256

The loop is defined in /home/eoseret/llm-attention/attention_v2.cpp:26-33.

Analyzed code is defined in /home/eoseret/llm-attention/attention_v2.cpp:26-27,30,33.

Warnings:

Non-innermost loop: analyzing only self part (ignoring child loops).
Ignoring paths for analysis
Too many paths. Rerun with max-paths=8
RecMII not computed since number of paths is unknown or > max_paths
Streams not analyzed 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 8 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 5.50 to 1.88 cycles (2.93x speedup).

Workaround

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

Vectorization

Your loop is probably not vectorized. Only 12% of vector register length is used (average across all SSE/AVX instructions). By vectorizing your loop, you can lower the cost of an iteration from 5.50 to 0.53 cycles (10.35x speedup).

Details

Store and arithmetical SSE/AVX 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:
- recompile with ffast-math (included in Ofast) to extend loop vectorization to FP reductions.
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)

Execution units bottlenecks

Performance is limited by:

reading data from caches/RAM (load units are a bottleneck)
writing data to caches/RAM (the store unit is a bottleneck)

By removing all these bottlenecks, you can lower the cost of an iteration from 5.50 to 3.00 cycles (1.83x speedup).

Workaround

Read less array elements
Write less array elements
Provide more information to your compiler:
- hardcode the bounds of the corresponding 'for' loop

No data for this section

Conversion instructions

Detected expensive conversion instructions.

Details

VCVTSD2SS (FP64 to FP32, scalar): 1 occurrences►
- /home/eoseret/llm-attention/attention_v2.cpp:33

Workaround

Avoid mixing data with different types. In particular, check if the type of constants is the same as array elements. Use double instead of single precision only when/where needed by numerical stability and avoid mixing precision. In C/C++, FP constants are double precision by default and must be suffixed by 'f' to make them single precision.

Type of elements and instruction set

No instructions are processing arithmetic or math operations on FP elements. This loop is probably writing/copying data or processing integer elements.

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 149 bytes. The binary loop is storing 12 bytes.

General properties

nb instructions	45
nb uops	44
loop length	245
used x86 registers	15
used mmx registers	0
used xmm registers	1
used ymm registers	0
used zmm registers	0
nb stack references	16

Front-end

ASSUMED MACRO FUSION FIT IN UOP CACHE

micro-operation queue	5.50 cycles
front end	5.50 cycles

Back-end

	P0	P1	P2	P3	P4	P5	P6	P7	P8	P9	P10	P11	P12	P13	P14	P15
uops	3.00	3.00	3.00	3.00	3.00	3.00	5.50	5.50	5.50	5.50	0.00	0.00	0.50	0.50	0.50	0.50
cycles	3.00	3.00	3.00	3.00	3.00	3.00	5.50	5.50	5.50	5.50	0.00	0.00	0.50	0.50	0.50	0.50

Execution ports to units layout:

P0: ALU
P1: ALU
P2: ALU
P3: ALU, BRU
P4: ALU, BRU
P5: ALU, BRU
P6 (512 bits): store address, load
P7 (512 bits): store address, load
P8 (512 bits): store address, load
P9 (512 bits): store address, load
P10 (512 bits): VPU, DIV/SQRT
P11 (512 bits): VPU, DIV/SQRT
P12 (512 bits): VPU
P13 (512 bits): VPU
P14 (512 bits): FP store data
P15 (512 bits): FP store data

Cycles executing div or sqrt instructions

Cycles summary

Front-end	5.50
Dispatch	5.50
Overall L1	5.50

Vectorization ratios

INT

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

all	33%
load	NA (no load vectorizable/vectorized instructions)
store	0%
mul	NA (no mul vectorizable/vectorized instructions)
add-sub	NA (no add-sub vectorizable/vectorized instructions)
fma	NA (no fma vectorizable/vectorized instructions)
div/sqrt	NA (no div/sqrt vectorizable/vectorized instructions)
other	50%

INT+FP

all	5%
load	0%
store	0%
mul	NA (no mul vectorizable/vectorized instructions)
add-sub	NA (no add-sub vectorizable/vectorized instructions)
fma	NA (no fma vectorizable/vectorized instructions)
div/sqrt	NA (no div/sqrt vectorizable/vectorized instructions)
other	16%

Vector efficiency ratios

INT

all	12%
load	12%
store	12%
mul	NA (no mul vectorizable/vectorized instructions)
add-sub	NA (no add-sub vectorizable/vectorized instructions)
fma	NA (no fma vectorizable/vectorized instructions)
other	10%

all	14%
load	NA (no load vectorizable/vectorized instructions)
store	6%
mul	NA (no mul vectorizable/vectorized instructions)
add-sub	NA (no add-sub vectorizable/vectorized instructions)
fma	NA (no fma vectorizable/vectorized instructions)
div/sqrt	NA (no div/sqrt vectorizable/vectorized instructions)
other	18%

INT+FP

all	12%
load	12%
store	9%
mul	NA (no mul vectorizable/vectorized instructions)
add-sub	NA (no add-sub vectorizable/vectorized instructions)
fma	NA (no fma vectorizable/vectorized instructions)
div/sqrt	NA (no div/sqrt vectorizable/vectorized instructions)
other	13%

Cycles and memory resources usage

Assuming all data fit into the L1 cache, each iteration of the binary loop takes 5.50 cycles. At this rate:

10% of peak load performance is reached (27.09 out of 256.00 bytes loaded per cycle (GB/s @ 1GHz))
1% of peak store performance is reached (2.18 out of 128.00 bytes stored per cycle (GB/s @ 1GHz))

Front-end bottlenecks

Performance is limited by instruction throughput (loading/decoding program instructions to execution core) (front-end is a bottleneck). By removing all these bottlenecks, you can lower the cost of an iteration from 5.50 to 3.00 cycles (1.83x speedup).

ASM code

In the binary file, the address of the loop is: 4e68

Instruction	Nb FU	P0	P1	P2	P3	P4	P5	P6	P7	P8	P9	P12	P13	P14	P15	Latency	Recip. throughput	Vectorization
MOV 0x120(%RSP),%RAX	1	0	0	0	0	0	0	0.25	0.25	0.25	0.25	0	0	0	0	3	0.25	N/A
MOV 0x68(%RSP),%RDX	1	0	0	0	0	0	0	0.25	0.25	0.25	0.25	0	0	0	0	3	0.25	N/A
VCVTSD2SS %XMM0,%XMM0,%XMM0	1	0	0	0	0	0	0	0	0	0	0	0.50	0.50	0	0	3	0.50	scal (12.5%)
LEA (%RAX,%RSI,1),%R9D	1	0.17	0.17	0.17	0.17	0.17	0.17	0	0	0	0	0	0	0	0	1	0.17	N/A
INC %RSI	1	0.17	0.17	0.17	0.17	0.17	0.17	0	0	0	0	0	0	0	0	1	0.17	N/A
VMOVSS %XMM0,(%RDX,%R9,4)	1	0	0	0	0	0	0	0.25	0.25	0.25	0.25	0	0	0.50	0.50	1	0.50	scal (6.3%)
MOV 0x28(%RSP),%R9	1	0	0	0	0	0	0	0.25	0.25	0.25	0.25	0	0	0	0	3	0.25	N/A
CMP %R9,%RSI	1	0.17	0.17	0.17	0.17	0.17	0.17	0	0	0	0	0	0	0	0	1	0.17	scal (12.5%)
JE 4df0 <main+0x2020>	1	0	0	0	0.33	0.33	0.33	0	0	0	0	0	0	0	0	0	0.33-0.50	N/A
CMP $0x3,%R9D	1	0.17	0.17	0.17	0.17	0.17	0.17	0	0	0	0	0	0	0	0	1	0.17	scal (6.3%)
JBE 4e8b <main+0x20bb>	1	0	0	0	0.33	0.33	0.33	0	0	0	0	0	0	0	0	0	0.33-0.50	N/A
MOV %ESI,%R9D	1	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0.13	N/A
ADD 0x98(%RSP),%R9D	1	0.17	0.17	0.17	0.17	0.17	0.17	0.25	0.25	0.25	0.25	0	0	0	0	1	0.25	N/A
SETB %R9B	1	0.17	0.17	0.17	0.17	0.17	0.17	0	0	0	0	0	0	0	0	1	0.17	N/A
OR 0xa0(%RSP),%R9B	1	0.17	0.17	0.17	0.17	0.17	0.17	0.25	0.25	0.25	0.25	0	0	0	0	1	0.25	N/A
JE 71e9 <main+0x4419>	1	0	0	0	0.33	0.33	0.33	0	0	0	0	0	0	0	0	0	0.33-0.50	N/A
CMPQ $0x7,0x98(%RSP)	1	0.17	0.17	0.17	0.17	0.17	0.17	0.25	0.25	0.25	0.25	0	0	0	0	1	0.25	scal (12.5%)
VXORPS %XMM0,%XMM0,%XMM0	1	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0.17	vect (25.0%)
MOV %RSI,0x140(%RSP)	1	0	0	0	0	0	0	0.25	0.25	0.25	0.25	0	0	0	0	4	0.50	scal (12.5%)
JAE 4ec0 <main+0x20f0>	1	0	0	0	0.33	0.33	0.33	0	0	0	0	0	0	0	0	0	0.33-0.50	N/A
MOV 0x60(%RSP),%R14	1	0	0	0	0	0	0	0.25	0.25	0.25	0.25	0	0	0	0	3	0.25	scal (12.5%)
MOV 0x48(%RSP),%R8	1	0	0	0	0	0	0	0.25	0.25	0.25	0.25	0	0	0	0	3	0.25	scal (12.5%)
XOR %R9D,%R9D	1	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0.17	N/A
JMP 5044 <main+0x2274>	1	0	0	0	0.33	0.33	0.33	0	0	0	0	0	0	0	0	0	0.50	N/A
MOV %RSI,%R10	1	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0.13	N/A
MOV 0x248(%RSP),%RAX	1	0	0	0	0	0	0	0.25	0.25	0.25	0.25	0	0	0	0	3	0.25	N/A
MOV 0x2c8(%RSP),%RDI	1	0	0	0	0	0	0	0.25	0.25	0.25	0.25	0	0	0	0	3	0.25	scal (12.5%)
MOV 0x2c0(%RSP),%RSI	1	0	0	0	0	0	0	0.25	0.25	0.25	0.25	0	0	0	0	3	0.25	N/A
MOV 0x2b8(%RSP),%R12	1	0	0	0	0	0	0	0.25	0.25	0.25	0.25	0	0	0	0	3	0.25	scal (12.5%)
MOV 0x2b0(%RSP),%R13	1	0	0	0	0	0	0	0.25	0.25	0.25	0.25	0	0	0	0	3	0.25	scal (12.5%)
MOV 0x2a8(%RSP),%R15	1	0	0	0	0	0	0	0.25	0.25	0.25	0.25	0	0	0	0	3	0.25	scal (12.5%)
MOV 0x60(%RSP),%R14	1	0	0	0	0	0	0	0.25	0.25	0.25	0.25	0	0	0	0	3	0.25	scal (12.5%)
MOV 0x48(%RSP),%R8	1	0	0	0	0	0	0	0.25	0.25	0.25	0.25	0	0	0	0	3	0.25	scal (12.5%)
MOV 0x2a0(%RSP),%RDX	1	0	0	0	0	0	0	0.25	0.25	0.25	0.25	0	0	0	0	3	0.25	N/A
XOR %R9D,%R9D	1	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0.17	N/A
NOPL (%RAX,%RAX,1)	1	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0.13	N/A
CMPQ $0,0x250(%RSP)	1	0.17	0.17	0.17	0.17	0.17	0.17	0.25	0.25	0.25	0.25	0	0	0	0	1	0.25	scal (12.5%)
MOV 0x140(%RSP),%RSI	1	0	0	0	0	0	0	0.25	0.25	0.25	0.25	0	0	0	0	3	0.25	N/A
JE 4e40 <main+0x2070>	1	0	0	0	0.33	0.33	0.33	0	0	0	0	0	0	0	0	0	0.33-0.50	N/A
MOV 0x250(%RSP),%R11	1	0	0	0	0	0	0	0.25	0.25	0.25	0.25	0	0	0	0	3	0.25	scal (12.5%)
MOV %RBX,%R10	1	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0.13	N/A
IMUL %R9,%R10	1	0.33	0.33	0.33	0	0	0	0	0	0	0	0	0	0	0	3	0.33	N/A
ADD %ECX,%R9D	1	0.17	0.17	0.17	0.17	0.17	0.17	0	0	0	0	0	0	0	0	1	0.17	N/A
ADD %RSI,%R10	1	0.17	0.17	0.17	0.17	0.17	0.17	0	0	0	0	0	0	0	0	1	0.17	N/A
JMP 4e40 <main+0x2070>	1	0	0	0	0.33	0.33	0.33	0	0	0	0	0	0	0	0	0	0.50	N/A

Function	main
Source file and lines	attention_v2.cpp:26-33
Module	attention-clang-znver5-256

The loop is defined in /home/eoseret/llm-attention/attention_v2.cpp:26-33.

Analyzed code is defined in /home/eoseret/llm-attention/attention_v2.cpp:26-27,30,33.

Warnings:

Non-innermost loop: analyzing only self part (ignoring child loops).
Ignoring paths for analysis
Too many paths. Rerun with max-paths=8
RecMII not computed since number of paths is unknown or > max_paths
Streams not analyzed 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 5.50 to 1.88 cycles (2.93x speedup).

Workaround

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

Vectorization

Details

Workaround

Try another compiler or update/tune your current one:
- recompile with ffast-math (included in Ofast) to extend loop vectorization to FP reductions.
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)

Execution units bottlenecks

Performance is limited by:

reading data from caches/RAM (load units are a bottleneck)
writing data to caches/RAM (the store unit is a bottleneck)

By removing all these bottlenecks, you can lower the cost of an iteration from 5.50 to 3.00 cycles (1.83x speedup).

Workaround

Read less array elements
Write less array elements
Provide more information to your compiler:
- hardcode the bounds of the corresponding 'for' loop

No data for this section

Conversion instructions

Detected expensive conversion instructions.

Details

VCVTSD2SS (FP64 to FP32, scalar): 1 occurrences►
- /home/eoseret/llm-attention/attention_v2.cpp:33

Workaround

Type of elements and instruction set

No instructions are processing arithmetic or math operations on FP elements. This loop is probably writing/copying data or processing integer elements.

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 149 bytes. The binary loop is storing 12 bytes.

General properties

nb instructions	45
nb uops	44
loop length	245
used x86 registers	15
used mmx registers	0
used xmm registers	1
used ymm registers	0
used zmm registers	0
nb stack references	16

Front-end

ASSUMED MACRO FUSION FIT IN UOP CACHE

micro-operation queue	5.50 cycles
front end	5.50 cycles

Back-end

	P0	P1	P2	P3	P4	P5	P6	P7	P8	P9	P10	P11	P12	P13	P14	P15
uops	3.00	3.00	3.00	3.00	3.00	3.00	5.50	5.50	5.50	5.50	0.00	0.00	0.50	0.50	0.50	0.50
cycles	3.00	3.00	3.00	3.00	3.00	3.00	5.50	5.50	5.50	5.50	0.00	0.00	0.50	0.50	0.50	0.50

Execution ports to units layout:

P0: ALU
P1: ALU
P2: ALU
P3: ALU, BRU
P4: ALU, BRU
P5: ALU, BRU
P6 (512 bits): store address, load
P7 (512 bits): store address, load
P8 (512 bits): store address, load
P9 (512 bits): store address, load
P10 (512 bits): VPU, DIV/SQRT
P11 (512 bits): VPU, DIV/SQRT
P12 (512 bits): VPU
P13 (512 bits): VPU
P14 (512 bits): FP store data
P15 (512 bits): FP store data

Cycles executing div or sqrt instructions

Cycles summary

Front-end	5.50
Dispatch	5.50
Overall L1	5.50

Vectorization ratios

INT

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

all	33%
load	NA (no load vectorizable/vectorized instructions)
store	0%
mul	NA (no mul vectorizable/vectorized instructions)
add-sub	NA (no add-sub vectorizable/vectorized instructions)
fma	NA (no fma vectorizable/vectorized instructions)
div/sqrt	NA (no div/sqrt vectorizable/vectorized instructions)
other	50%

INT+FP

all	5%
load	0%
store	0%
mul	NA (no mul vectorizable/vectorized instructions)
add-sub	NA (no add-sub vectorizable/vectorized instructions)
fma	NA (no fma vectorizable/vectorized instructions)
div/sqrt	NA (no div/sqrt vectorizable/vectorized instructions)
other	16%

Vector efficiency ratios

INT

all	12%
load	12%
store	12%
mul	NA (no mul vectorizable/vectorized instructions)
add-sub	NA (no add-sub vectorizable/vectorized instructions)
fma	NA (no fma vectorizable/vectorized instructions)
other	10%

all	14%
load	NA (no load vectorizable/vectorized instructions)
store	6%
mul	NA (no mul vectorizable/vectorized instructions)
add-sub	NA (no add-sub vectorizable/vectorized instructions)
fma	NA (no fma vectorizable/vectorized instructions)
div/sqrt	NA (no div/sqrt vectorizable/vectorized instructions)
other	18%

INT+FP

all	12%
load	12%
store	9%
mul	NA (no mul vectorizable/vectorized instructions)
add-sub	NA (no add-sub vectorizable/vectorized instructions)
fma	NA (no fma vectorizable/vectorized instructions)
div/sqrt	NA (no div/sqrt vectorizable/vectorized instructions)
other	13%

Cycles and memory resources usage

Assuming all data fit into the L1 cache, each iteration of the binary loop takes 5.50 cycles. At this rate:

10% of peak load performance is reached (27.09 out of 256.00 bytes loaded per cycle (GB/s @ 1GHz))
1% of peak store performance is reached (2.18 out of 128.00 bytes stored per cycle (GB/s @ 1GHz))

Front-end bottlenecks

ASM code

In the binary file, the address of the loop is: 4e68

Instruction	Nb FU	P0	P1	P2	P3	P4	P5	P6	P7	P8	P9	P12	P13	P14	P15	Latency	Recip. throughput	Vectorization
MOV 0x120(%RSP),%RAX	1	0	0	0	0	0	0	0.25	0.25	0.25	0.25	0	0	0	0	3	0.25	N/A
MOV 0x68(%RSP),%RDX	1	0	0	0	0	0	0	0.25	0.25	0.25	0.25	0	0	0	0	3	0.25	N/A
VCVTSD2SS %XMM0,%XMM0,%XMM0	1	0	0	0	0	0	0	0	0	0	0	0.50	0.50	0	0	3	0.50	scal (12.5%)
LEA (%RAX,%RSI,1),%R9D	1	0.17	0.17	0.17	0.17	0.17	0.17	0	0	0	0	0	0	0	0	1	0.17	N/A
INC %RSI	1	0.17	0.17	0.17	0.17	0.17	0.17	0	0	0	0	0	0	0	0	1	0.17	N/A
VMOVSS %XMM0,(%RDX,%R9,4)	1	0	0	0	0	0	0	0.25	0.25	0.25	0.25	0	0	0.50	0.50	1	0.50	scal (6.3%)
MOV 0x28(%RSP),%R9	1	0	0	0	0	0	0	0.25	0.25	0.25	0.25	0	0	0	0	3	0.25	N/A
CMP %R9,%RSI	1	0.17	0.17	0.17	0.17	0.17	0.17	0	0	0	0	0	0	0	0	1	0.17	scal (12.5%)
JE 4df0 <main+0x2020>	1	0	0	0	0.33	0.33	0.33	0	0	0	0	0	0	0	0	0	0.33-0.50	N/A
CMP $0x3,%R9D	1	0.17	0.17	0.17	0.17	0.17	0.17	0	0	0	0	0	0	0	0	1	0.17	scal (6.3%)
JBE 4e8b <main+0x20bb>	1	0	0	0	0.33	0.33	0.33	0	0	0	0	0	0	0	0	0	0.33-0.50	N/A
MOV %ESI,%R9D	1	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0.13	N/A
ADD 0x98(%RSP),%R9D	1	0.17	0.17	0.17	0.17	0.17	0.17	0.25	0.25	0.25	0.25	0	0	0	0	1	0.25	N/A
SETB %R9B	1	0.17	0.17	0.17	0.17	0.17	0.17	0	0	0	0	0	0	0	0	1	0.17	N/A
OR 0xa0(%RSP),%R9B	1	0.17	0.17	0.17	0.17	0.17	0.17	0.25	0.25	0.25	0.25	0	0	0	0	1	0.25	N/A
JE 71e9 <main+0x4419>	1	0	0	0	0.33	0.33	0.33	0	0	0	0	0	0	0	0	0	0.33-0.50	N/A
CMPQ $0x7,0x98(%RSP)	1	0.17	0.17	0.17	0.17	0.17	0.17	0.25	0.25	0.25	0.25	0	0	0	0	1	0.25	scal (12.5%)
VXORPS %XMM0,%XMM0,%XMM0	1	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0.17	vect (25.0%)
MOV %RSI,0x140(%RSP)	1	0	0	0	0	0	0	0.25	0.25	0.25	0.25	0	0	0	0	4	0.50	scal (12.5%)
JAE 4ec0 <main+0x20f0>	1	0	0	0	0.33	0.33	0.33	0	0	0	0	0	0	0	0	0	0.33-0.50	N/A
MOV 0x60(%RSP),%R14	1	0	0	0	0	0	0	0.25	0.25	0.25	0.25	0	0	0	0	3	0.25	scal (12.5%)
MOV 0x48(%RSP),%R8	1	0	0	0	0	0	0	0.25	0.25	0.25	0.25	0	0	0	0	3	0.25	scal (12.5%)
XOR %R9D,%R9D	1	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0.17	N/A
JMP 5044 <main+0x2274>	1	0	0	0	0.33	0.33	0.33	0	0	0	0	0	0	0	0	0	0.50	N/A
MOV %RSI,%R10	1	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0.13	N/A
MOV 0x248(%RSP),%RAX	1	0	0	0	0	0	0	0.25	0.25	0.25	0.25	0	0	0	0	3	0.25	N/A
MOV 0x2c8(%RSP),%RDI	1	0	0	0	0	0	0	0.25	0.25	0.25	0.25	0	0	0	0	3	0.25	scal (12.5%)
MOV 0x2c0(%RSP),%RSI	1	0	0	0	0	0	0	0.25	0.25	0.25	0.25	0	0	0	0	3	0.25	N/A
MOV 0x2b8(%RSP),%R12	1	0	0	0	0	0	0	0.25	0.25	0.25	0.25	0	0	0	0	3	0.25	scal (12.5%)
MOV 0x2b0(%RSP),%R13	1	0	0	0	0	0	0	0.25	0.25	0.25	0.25	0	0	0	0	3	0.25	scal (12.5%)
MOV 0x2a8(%RSP),%R15	1	0	0	0	0	0	0	0.25	0.25	0.25	0.25	0	0	0	0	3	0.25	scal (12.5%)
MOV 0x60(%RSP),%R14	1	0	0	0	0	0	0	0.25	0.25	0.25	0.25	0	0	0	0	3	0.25	scal (12.5%)
MOV 0x48(%RSP),%R8	1	0	0	0	0	0	0	0.25	0.25	0.25	0.25	0	0	0	0	3	0.25	scal (12.5%)
MOV 0x2a0(%RSP),%RDX	1	0	0	0	0	0	0	0.25	0.25	0.25	0.25	0	0	0	0	3	0.25	N/A
XOR %R9D,%R9D	1	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0.17	N/A
NOPL (%RAX,%RAX,1)	1	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0.13	N/A
CMPQ $0,0x250(%RSP)	1	0.17	0.17	0.17	0.17	0.17	0.17	0.25	0.25	0.25	0.25	0	0	0	0	1	0.25	scal (12.5%)
MOV 0x140(%RSP),%RSI	1	0	0	0	0	0	0	0.25	0.25	0.25	0.25	0	0	0	0	3	0.25	N/A
JE 4e40 <main+0x2070>	1	0	0	0	0.33	0.33	0.33	0	0	0	0	0	0	0	0	0	0.33-0.50	N/A
MOV 0x250(%RSP),%R11	1	0	0	0	0	0	0	0.25	0.25	0.25	0.25	0	0	0	0	3	0.25	scal (12.5%)
MOV %RBX,%R10	1	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0.13	N/A
IMUL %R9,%R10	1	0.33	0.33	0.33	0	0	0	0	0	0	0	0	0	0	0	3	0.33	N/A
ADD %ECX,%R9D	1	0.17	0.17	0.17	0.17	0.17	0.17	0	0	0	0	0	0	0	0	1	0.17	N/A
ADD %RSI,%R10	1	0.17	0.17	0.17	0.17	0.17	0.17	0	0	0	0	0	0	0	0	1	0.17	N/A
JMP 4e40 <main+0x2070>	1	0	0	0	0.33	0.33	0.33	0	0	0	0	0	0	0	0	0	0.50	N/A

Report Configuration

Code clean check

Workaround

Vectorization

Details

Workaround

Execution units bottlenecks

Workaround

Conversion instructions

Details

Workaround

Type of elements and instruction set

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

General properties

Front-end

Back-end

Cycles summary

Vectorization ratios

Vector efficiency ratios

Cycles and memory resources usage

Front-end bottlenecks

ASM code

Code clean check

Workaround

Vectorization

Details

Workaround

Execution units bottlenecks

Workaround

Conversion instructions

Details

Workaround

Type of elements and instruction set

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

General properties

Front-end

Back-end

Cycles summary

Vectorization ratios

Vector efficiency ratios

Cycles and memory resources usage

Front-end bottlenecks

ASM code