change strided_slice when step<0.

[hbwx24]

PR types

Function optimization

PR changes

OPs

Describe

strided_slice:当step<0时，没有与numpy对齐。

import numpy as np
import paddle


array = np.arange(5)


pt = paddle.to_tensor(array)

sl = paddle.strided_slice(pt, axes=[0, ], starts=[3, ], ends=[1, ], strides=[-2, ])
print("array:", array)
print("numpy:", array[3:1:-2])
print("paddle:", sl)

# 输出
# array: [0 1 2 3 4]
# numpy: [3]
# paddle: Tensor(shape=[1], dtype=int64, place=CPUPlace, stop_gradient=True, [2])

[paddle-bot-old]

Thanks for your contribution!
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[chenwhql]

LGTM

[TeslaZhao]

LGTM