### Description
Hello we(@lixing-star) are the developers of loongson team.

We add 128 (lsx), 256 (lasx) vector optimization code for the loongarch
architecture


[100% tests passed, 0 tests failed out of
7](https://cloud.a-boat.cn:2021/api/public/dl/6831z1Bi?inline=true)

### Development Environments1
```
CPU: 
    Loongson-3C5000L
uname -a:  
    Linux localhost.localdomain 4.19.190-6.4.lns8.loongarch64 #1 SMP Thu Jul 14 12:08:04 CST 2022 loongarch64 loongarch64 loongarch64 GNU/Linux

```
### LonngArch Documents
- [LoongArch Reference Manual - Volume 1: Basic Architecture: This
manual describes the basic part of the LoongArch
architecture.](https://loongson.github.io/LoongArch-Documentation/LoongArch-Vol1-EN.html)
- [LoongArch ELF psABI: This manual describes the LoongArch ELF
psABI.](https://loongson.github.io/LoongArch-Documentation/LoongArch-ELF-ABI-EN.html)
-
[more](https://loongson.github.io/LoongArch-Documentation/README-EN.html)

### Description
Add [Lean Attention](https://arxiv.org/abs/2405.10480) and the
integration with MultiHeadAttention operator for LLM in GPU.

LeanAttention speeds up self-attention for the token-generation phase
(decode-phase) of decoder-only transformer models, especially on long
context lengths.

- [x] Initial implementation of Lean Attention (by Srikant Bharadwaj)
- [x] Integration with MultiHeadAttention operator
- [x] Add parity tests
- [x] Add benchmark

#### Implementation Details

(1) Lean Attention is enabled in build for Linux, and disabled for
Windows
(2) Lean Attention is disabled by default. Need enable it through cuda
provider option sdpa_kernel, or use environment variable
`ORT_ENABLE_LEAN_ATTENTION=1`
(3) It only works for token-generation (sequence_length==1,
past_sequence_length > 0).
(4) Like flash attention, it only works in Ampere or newer GPU.

We can revisit #1 and #2 after comparing with
DecoderMaskedMultiHeadAttention and XQA kernels.

#### Benchmark

```
cd onnxruntime/test/python/transformers 
/bin/bash benchmark_mha.sh lean
```

Example outputs in H100:

Note that past and present does not share buffer for MHA for now, so we
can see low tflops. The relative ratio will change after buffer sharing
is enabled. But we expect that the order (kernel A is faster than B)
will remain the same after buffer sharing is enabled.

Note that common settings `sequence_length=1;
causal=True;attn_bias=None;cuda_graph=False` are not shown in the below
table.

batch_size | past_sequence_length | num_heads | head_size |
average_latency | tflops | kernel
-- | -- | -- | -- | -- | -- | --
1 | 512 | 16 | 64 | 0.000059 | 0.0178 | ort:flash
1 | 512 | 16 | 64 | 0.000068 | 0.0155 | ort:efficient
1 | 512 | 16 | 64 | 0.000065 | 0.0161 | ort:math
1 | 512 | 16 | 64 | 0.000060 | 0.0176 | ort:lean
1 | 512 | 32 | 128 | 0.000062 | 0.0674 | ort:flash
1 | 512 | 32 | 128 | 0.000064 | 0.0661 | ort:efficient
1 | 512 | 32 | 128 | 0.000067 | 0.0625 | ort:math
1 | 512 | 32 | 128 | 0.000062 | 0.0678 | ort:lean
1 | 1024 | 16 | 64 | 0.000061 | 0.0345 | ort:flash
1 | 1024 | 16 | 64 | 0.000086 | 0.0244 | ort:efficient
1 | 1024 | 16 | 64 | 0.000065 | 0.0322 | ort:math
1 | 1024 | 16 | 64 | 0.000063 | 0.0332 | ort:lean
1 | 1024 | 32 | 128 | 0.000075 | 0.1125 | ort:flash
1 | 1024 | 32 | 128 | 0.000088 | 0.0951 | ort:efficient
1 | 1024 | 32 | 128 | 0.000079 | 0.1068 | ort:math
1 | 1024 | 32 | 128 | 0.000072 | 0.1171 | ort:lean
1 | 2048 | 16 | 64 | 0.000069 | 0.0606 | ort:flash
1 | 2048 | 16 | 64 | 0.000125 | 0.0336 | ort:efficient
1 | 2048 | 16 | 64 | 0.000064 | 0.0655 | ort:lean
1 | 2048 | 32 | 128 | 0.000098 | 0.1720 | ort:flash
1 | 2048 | 32 | 128 | 0.000132 | 0.1270 | ort:efficient
1 | 2048 | 32 | 128 | 0.000092 | 0.1828 | ort:lean
1 | 4096 | 16 | 64 | 0.000076 | 0.1097 | ort:flash
1 | 4096 | 16 | 64 | 0.000207 | 0.0406 | ort:efficient
1 | 4096 | 16 | 64 | 0.000069 | 0.1209 | ort:lean
1 | 4096 | 32 | 128 | 0.000140 | 0.2394 | ort:flash
1 | 4096 | 32 | 128 | 0.000213 | 0.1575 | ort:efficient
1 | 4096 | 32 | 128 | 0.000139 | 0.2419 | ort:lean
1 | 8192 | 16 | 64 | 0.000104 | 0.1609 | ort:flash
1 | 8192 | 16 | 64 | 0.000392 | 0.0428 | ort:efficient
1 | 8192 | 16 | 64 | 0.000093 | 0.1809 | ort:lean
1 | 8192 | 32 | 128 | 0.000212 | 0.3160 | ort:flash
1 | 8192 | 32 | 128 | 0.000360 | 0.1866 | ort:efficient
1 | 8192 | 32 | 128 | 0.000212 | 0.3162 | ort:lean
1 | 16384 | 16 | 64 | 0.000139 | 0.2410 | ort:flash
1 | 16384 | 16 | 64 | 0.000731 | 0.0459 | ort:efficient
1 | 16384 | 16 | 64 | 0.000136 | 0.2465 | ort:lean
1 | 16384 | 32 | 128 | 0.000361 | 0.3722 | ort:flash
1 | 16384 | 32 | 128 | 0.000667 | 0.2014 | ort:efficient
1 | 16384 | 32 | 128 | 0.000357 | 0.3765 | ort:lean
1 | 32768 | 16 | 64 | 0.000210 | 0.3194 | ort:flash
1 | 32768 | 16 | 64 | 0.001428 | 0.0470 | ort:efficient
1 | 32768 | 16 | 64 | 0.000209 | 0.3211 | ort:lean
1 | 32768 | 32 | 128 | 0.000659 | 0.4074 | ort:flash
1 | 32768 | 32 | 128 | 0.001270 | 0.2114 | ort:efficient
1 | 32768 | 32 | 128 | 0.000651 | 0.4123 | ort:lean
1 | 65536 | 16 | 64 | 0.000355 | 0.3785 | ort:flash
1 | 65536 | 16 | 64 | 0.002736 | 0.0491 | ort:efficient
1 | 65536 | 16 | 64 | 0.000349 | 0.3845 | ort:lean
1 | 65536 | 32 | 128 | 0.001251 | 0.4290 | ort:flash
1 | 65536 | 32 | 128 | 0.002480 | 0.2165 | ort:efficient
1 | 65536 | 32 | 128 | 0.001239 | 0.4333 | ort:lean
4 | 512 | 16 | 64 | 0.000063 | 0.0665 | ort:flash
4 | 512 | 16 | 64 | 0.000069 | 0.0607 | ort:efficient
4 | 512 | 16 | 64 | 0.000066 | 0.0634 | ort:math
4 | 512 | 16 | 64 | 0.000062 | 0.0674 | ort:lean
4 | 512 | 32 | 128 | 0.000100 | 0.1677 | ort:flash
4 | 512 | 32 | 128 | 0.000099 | 0.1703 | ort:efficient
4 | 512 | 32 | 128 | 0.000108 | 0.1557 | ort:math
4 | 512 | 32 | 128 | 0.000092 | 0.1818 | ort:lean
4 | 1024 | 16 | 64 | 0.000077 | 0.1094 | ort:flash
4 | 1024 | 16 | 64 | 0.000099 | 0.0850 | ort:efficient
4 | 1024 | 16 | 64 | 0.000081 | 0.1038 | ort:math
4 | 1024 | 16 | 64 | 0.000072 | 0.1161 | ort:lean
4 | 1024 | 32 | 128 | 0.000143 | 0.2343 | ort:flash
4 | 1024 | 32 | 128 | 0.000137 | 0.2447 | ort:efficient
4 | 1024 | 32 | 128 | 0.000150 | 0.2245 | ort:math
4 | 1024 | 32 | 128 | 0.000135 | 0.2496 | ort:lean
4 | 2048 | 16 | 64 | 0.000096 | 0.1757 | ort:flash
4 | 2048 | 16 | 64 | 0.000156 | 0.1078 | ort:efficient
4 | 2048 | 16 | 64 | 0.000089 | 0.1892 | ort:lean
4 | 2048 | 32 | 128 | 0.000223 | 0.3010 | ort:flash
4 | 2048 | 32 | 128 | 0.000217 | 0.3101 | ort:efficient
4 | 2048 | 32 | 128 | 0.000209 | 0.3209 | ort:lean
4 | 4096 | 16 | 64 | 0.000137 | 0.2448 | ort:flash
4 | 4096 | 16 | 64 | 0.000256 | 0.1312 | ort:efficient
4 | 4096 | 16 | 64 | 0.000133 | 0.2530 | ort:lean
4 | 4096 | 32 | 128 | 0.000389 | 0.3450 | ort:flash
4 | 4096 | 32 | 128 | 0.000376 | 0.3574 | ort:efficient
4 | 4096 | 32 | 128 | 0.000354 | 0.3794 | ort:lean
4 | 8192 | 16 | 64 | 0.000210 | 0.3198 | ort:flash
4 | 8192 | 16 | 64 | 0.000453 | 0.1480 | ort:efficient
4 | 8192 | 16 | 64 | 0.000206 | 0.3260 | ort:lean
4 | 8192 | 32 | 128 | 0.000725 | 0.3705 | ort:flash
4 | 8192 | 32 | 128 | 0.000693 | 0.3874 | ort:efficient
4 | 8192 | 32 | 128 | 0.000653 | 0.4114 | ort:lean
4 | 16384 | 16 | 64 | 0.000355 | 0.3782 | ort:flash
4 | 16384 | 16 | 64 | 0.000849 | 0.1581 | ort:efficient
4 | 16384 | 16 | 64 | 0.000346 | 0.3874 | ort:lean
4 | 16384 | 32 | 128 | 0.001395 | 0.3848 | ort:flash
4 | 16384 | 32 | 128 | 0.001337 | 0.4017 | ort:efficient
4 | 16384 | 32 | 128 | 0.001252 | 0.4288 | ort:lean
4 | 32768 | 16 | 64 | 0.000647 | 0.4146 | ort:flash
4 | 32768 | 16 | 64 | 0.001649 | 0.1628 | ort:efficient
4 | 32768 | 16 | 64 | 0.000639 | 0.4204 | ort:lean
4 | 32768 | 32 | 128 | 0.002721 | 0.3947 | ort:flash
4 | 32768 | 32 | 128 | 0.002601 | 0.4128 | ort:efficient
4 | 32768 | 32 | 128 | 0.002434 | 0.4411 | ort:lean
4 | 65536 | 16 | 64 | 0.001231 | 0.4361 | ort:flash
4 | 65536 | 16 | 64 | 0.003238 | 0.1658 | ort:efficient
4 | 65536 | 16 | 64 | 0.001217 | 0.4412 | ort:lean
4 | 65536 | 32 | 128 | 0.005357 | 0.4009 | ort:flash
4 | 65536 | 32 | 128 | 0.005118 | 0.4196 | ort:efficient
4 | 65536 | 32 | 128 | 0.004781 | 0.4492 | ort:lean
16 | 512 | 16 | 64 | 0.000098 | 0.1724 | ort:flash
16 | 512 | 16 | 64 | 0.000104 | 0.1616 | ort:efficient
16 | 512 | 16 | 64 | 0.000118 | 0.1420 | ort:math
16 | 512 | 16 | 64 | 0.000087 | 0.1926 | ort:lean
16 | 512 | 32 | 128 | 0.000220 | 0.3062 | ort:flash
16 | 512 | 32 | 128 | 0.000208 | 0.3237 | ort:efficient
16 | 512 | 32 | 128 | 0.000237 | 0.2838 | ort:math
16 | 512 | 32 | 128 | 0.000209 | 0.3216 | ort:lean
16 | 1024 | 16 | 64 | 0.000136 | 0.2465 | ort:flash
16 | 1024 | 16 | 64 | 0.000150 | 0.2235 | ort:efficient
16 | 1024 | 16 | 64 | 0.000148 | 0.2266 | ort:math
16 | 1024 | 16 | 64 | 0.000129 | 0.2611 | ort:lean
16 | 1024 | 32 | 128 | 0.000367 | 0.3663 | ort:flash
16 | 1024 | 32 | 128 | 0.000351 | 0.3829 | ort:efficient
16 | 1024 | 32 | 128 | 0.000400 | 0.3357 | ort:math
16 | 1024 | 32 | 128 | 0.000349 | 0.3853 | ort:lean
16 | 2048 | 16 | 64 | 0.000209 | 0.3206 | ort:flash
16 | 2048 | 16 | 64 | 0.000243 | 0.2762 | ort:efficient
16 | 2048 | 16 | 64 | 0.000201 | 0.3338 | ort:lean
16 | 2048 | 32 | 128 | 0.000671 | 0.4002 | ort:flash
16 | 2048 | 32 | 128 | 0.000645 | 0.4163 | ort:efficient
16 | 2048 | 32 | 128 | 0.000642 | 0.4185 | ort:lean
16 | 4096 | 16 | 64 | 0.000360 | 0.3732 | ort:flash
16 | 4096 | 16 | 64 | 0.000425 | 0.3162 | ort:efficient
16 | 4096 | 16 | 64 | 0.000341 | 0.3933 | ort:lean
16 | 4096 | 32 | 128 | 0.001292 | 0.4156 | ort:flash
16 | 4096 | 32 | 128 | 0.001251 | 0.4291 | ort:efficient
16 | 4096 | 32 | 128 | 0.001241 | 0.4327 | ort:lean
16 | 8192 | 16 | 64 | 0.000666 | 0.4030 | ort:flash
16 | 8192 | 16 | 64 | 0.000804 | 0.3339 | ort:efficient
16 | 8192 | 16 | 64 | 0.000627 | 0.4283 | ort:lean
16 | 8192 | 32 | 128 | 0.002541 | 0.4226 | ort:flash
16 | 8192 | 32 | 128 | 0.002454 | 0.4376 | ort:efficient
16 | 8192 | 32 | 128 | 0.002438 | 0.4405 | ort:lean
16 | 16384 | 16 | 64 | 0.001292 | 0.4156 | ort:flash
16 | 16384 | 16 | 64 | 0.001571 | 0.3417 | ort:efficient
16 | 16384 | 16 | 64 | 0.001217 | 0.4411 | ort:lean
16 | 16384 | 32 | 128 | 0.005042 | 0.4260 | ort:flash
16 | 16384 | 32 | 128 | 0.004859 | 0.4420 | ort:efficient
16 | 16384 | 32 | 128 | 0.004827 | 0.4449 | ort:lean
16 | 32768 | 16 | 64 | 0.002537 | 0.4233 | ort:flash
16 | 32768 | 16 | 64 | 0.003103 | 0.3461 | ort:efficient
16 | 32768 | 16 | 64 | 0.002385 | 0.4501 | ort:lean
16 | 32768 | 32 | 128 | 0.009961 | 0.4312 | ort:flash
16 | 32768 | 32 | 128 | 0.009605 | 0.4472 | ort:efficient
16 | 32768 | 32 | 128 | 0.009524 | 0.4510 | ort:lean
16 | 65536 | 16 | 64 | 0.005019 | 0.4279 | ort:flash
16 | 65536 | 16 | 64 | 0.006133 | 0.3502 | ort:efficient
16 | 65536 | 16 | 64 | 0.004703 | 0.4566 | ort:lean
16 | 65536 | 32 | 128 | 0.019746 | 0.4350 | ort:flash
16 | 65536 | 32 | 128 | 0.019027 | 0.4515 | ort:efficient
16 | 65536 | 32 | 128 | 0.018864 | 0.4554 | ort:lean

### Motivation and Context
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