Implement Var

[cognaiger9]

• Added backward Var operation and kernel.
• Added driver test and gtest for Var.

When comparing the newly developed miopen var kernel with ROCm, there's performance improvement for a specific range of input sizes.(1024 ~ 1024 * 1024 * 2)

Type	Direction	geomean
fp32	bwd	3.61
fp16	bwd	3.9
bfp16	bwd	4.28

float32

op_name	dtype	size	dim	contiguous	direction	ROCm	MIOpen	Improvement
Var	float32	[2048 1 1]	[0]	contiguous	bwd	29150	9689	3.01
Var	float32	[2048 1 1]	[0]	noncontiguous	bwd	29150	9227	3.16
Var	float32	[8192 1 1]	[0]	contiguous	bwd	27918	9227	3.03
Var	float32	[8192 1 1]	[0]	noncontiguous	bwd	29790	8391	3.55
Var	float32	[65536 1 1]	[0]	contiguous	bwd	38894	9476	4.10
Var	float32	[65536 1 1]	[0]	noncontiguous	bwd	41230	9102	4.53
Var	float32	[80 40 1]	[0]	contiguous	bwd	42462	9209	4.61
Var	float32	[80 40 1]	[0]	noncontiguous	bwd	41486	12604	3.29
Var	float32	[80 250 1]	[0]	contiguous	bwd	35838	8675	4.13
Var	float32	[80 250 1]	[0]	noncontiguous	bwd	35998	12427	2.90
Var	float32	[40 50 30]	[0]	contiguous	bwd	35406	9173	3.86
Var	float32	[40 50 30]	[0]	noncontiguous	bwd	39469	15147	2.61
Var	float32	[30 50 10]	[0]	contiguous	bwd	42814	8373	5.11
Var	float32	[30 50 10]	[0]	noncontiguous	bwd	37678	13173	2.86
Var	float32	[50 40 50]	[0]	contiguous	bwd	36910	9422	3.92
Var	float32	[50 40 50]	[0]	noncontiguous	bwd	43630	16658	2.62
Var	float32	[40 60 10]	[0]	contiguous	bwd	37374	8018	4.66
Var	float32	[40 60 10]	[0]	noncontiguous	bwd	37134	12604	2.95
Var	float32	[30 50 20]	[1]	contiguous	bwd	38462	8480	4.54
Var	float32	[30 50 20]	[1]	noncontiguous	bwd	39870	14169	2.81

float16

op_name	dtype	size	dim	contiguous	direction	ROCm	MIOpen	Improvement
Var	float16	[2048 1 1]	[0]	contiguous	bwd	36558	9689	3.77
Var	float16	[2048 1 1]	[0]	noncontiguous	bwd	33518	9440	3.55
Var	float16	[8192 1 1]	[0]	contiguous	bwd	31230	9653	3.24
Var	float16	[8192 1 1]	[0]	noncontiguous	bwd	33070	9760	3.39
Var	float16	[65536 1 1]	[0]	contiguous	bwd	37726	9671	3.90
Var	float16	[65536 1 1]	[0]	noncontiguous	bwd	42126	9475	4.45
Var	float16	[80 40 1]	[0]	contiguous	bwd	46318	9938	4.66
Var	float16	[80 40 1]	[0]	noncontiguous	bwd	52381	12533	4.18
Var	float16	[80 250 1]	[0]	contiguous	bwd	41342	8853	4.67
Var	float16	[80 250 1]	[0]	noncontiguous	bwd	43662	13013	3.36
Var	float16	[40 50 30]	[0]	contiguous	bwd	40590	8409	4.83
Var	float16	[40 50 30]	[0]	noncontiguous	bwd	45086	15982	2.82
Var	float16	[30 50 10]	[0]	contiguous	bwd	40398	9137	4.42
Var	float16	[30 50 10]	[0]	noncontiguous	bwd	45101	14187	3.18
Var	float16	[50 40 50]	[0]	contiguous	bwd	43678	8960	4.87
Var	float16	[50 40 50]	[0]	noncontiguous	bwd	49054	17778	2.76
Var	float16	[40 60 10]	[0]	contiguous	bwd	40318	9333	4.32
Var	float16	[40 60 10]	[0]	noncontiguous	bwd	45102	13511	3.34
Var	float16	[30 50 20]	[1]	contiguous	bwd	43662	8551	5.11
Var	float16	[30 50 20]	[1]	noncontiguous	bwd	45870	13795	3.33

bfloat16

op_name	dtype	size	dim	contiguous	direction	ROCm	MIOpen	Improvement
Var	bfloat16	[2048 1 1]	[0]	contiguous	bwd	37502	10186	3.68
Var	bfloat16	[2048 1 1]	[0]	noncontiguous	bwd	34718	9778	3.55
Var	bfloat16	[8192 1 1]	[0]	contiguous	bwd	34334	9138	3.76
Var	bfloat16	[8192 1 1]	[0]	noncontiguous	bwd	37086	8746	4.24
Var	bfloat16	[65536 1 1]	[0]	contiguous	bwd	40846	8906	4.59
Var	bfloat16	[65536 1 1]	[0]	noncontiguous	bwd	44606	8693	5.13
Var	bfloat16	[80 40 1]	[0]	contiguous	bwd	50205	9333	5.38
Var	bfloat16	[80 40 1]	[0]	noncontiguous	bwd	52909	12729	4.16
Var	bfloat16	[80 250 1]	[0]	contiguous	bwd	42862	9618	4.46
Var	bfloat16	[80 250 1]	[0]	noncontiguous	bwd	46174	12906	3.58
Var	bfloat16	[40 50 30]	[0]	contiguous	bwd	45166	9439	4.79
Var	bfloat16	[40 50 30]	[0]	noncontiguous	bwd	49197	16035	3.07
Var	bfloat16	[30 50 10]	[0]	contiguous	bwd	46702	8960	5.21
Var	bfloat16	[30 50 10]	[0]	noncontiguous	bwd	51310	12871	3.99
Var	bfloat16	[50 40 50]	[0]	contiguous	bwd	46942	8995	5.22
Var	bfloat16	[50 40 50]	[0]	noncontiguous	bwd	53149	17760	2.99
Var	bfloat16	[40 60 10]	[0]	contiguous	bwd	43854	8622	5.09
Var	bfloat16	[40 60 10]	[0]	noncontiguous	bwd	50142	14400	3.48
Var	bfloat16	[30 50 20]	[1]	contiguous	bwd	49310	8711	5.66
Var	bfloat16	[30 50 20]	[1]	noncontiguous	bwd	50670	14009	3.62