softshrink lowering (pytorch#105603)

Fixes pytorch#105563 Pull Request resolved: pytorch#105603 Approved by: https://github.com/Chillee

Author: msaroufim

test/inductor/test_torchinductor.py

@@ -2035,6 +2035,19 @@ def fn(a):
  with self.assertRaisesRegex(RuntimeError, ""):
  fn(torch.randn(1, 5))
 
+ def test_softshrink_backward(self):
+ grad_output = torch.randn(1)
+ lambd = 0.5
+
+ def fn(a, grad_output, lambd):
+ a = a.cos()
+ return torch.ops.aten.softshrink_backward(grad_output, a, lambd)
+
+ self.common(
+ fn,
+ (torch.randn(10), grad_output, lambd),
+ )
+
  def test_inductor_assert(self):
  @torch._dynamo.optimize("inductor", dynamic=True)
  def fn(a):

torch/_inductor/lowering.py

@@ -1801,7 +1801,6 @@ def apply_constraint(arg, fx_arg):
 make_fallback(aten.reflection_pad1d_backward)
 make_fallback(aten.replication_pad1d_backward)
 make_fallback(aten.soft_margin_loss_backward, warn=False)
-make_fallback(aten.softshrink_backward, warn=False)
 make_fallback(aten.linalg_pinv.atol_rtol_tensor)
 make_fallback(aten.segment_reduce.default)
 make_fallback(aten._segment_reduce_backward.default)