[Pallas] Simplify sign and erf_inv tests

Removed the method to locally enabling x64 using:

```python
with contextlib.ExitStack() as stack:
  if jnp.dtype(dtype).itemsize == 8:
    stack.enter_context(config.enable_x64(True))
```

This is because we can determine whether a test is running in x64 environment by checking the value of `jax.config.x64_enabled`. There is no need to locally enabling x64.

PiperOrigin-RevId: 677019633

tests/pallas/ops_test.py

@@ -669,21 +669,25 @@ def run(interpret=False):
       actual = run(False)
       self.assertAllClose(actual, expected)
 
-  SIGN_PARAMS = [
-    (jnp.int32, (-3, 0, 5)),
-    (jnp.uint32, (0, 5)),
-    (jnp.float32, (-3.2, -0., 0., 5.1, jnp.nan, jnp.inf, -jnp.inf)),
-    (jnp.float64, (-3.2, -0., 0., 5.1, jnp.nan, jnp.inf, -jnp.inf)),
-  ]
-
   @parameterized.named_parameters(
       (f"{dtype.__name__}_{value}", dtype, value)
-      for dtype, values in SIGN_PARAMS
+      for dtypes, values in [
+          ((jnp.uint16, jnp.uint32, jnp.uint64), (0, 5)),
+          ((jnp.int16, jnp.int32, jnp.int64), (-3, 0, 5)),
+          (
+              (jnp.float16, jnp.float32, jnp.float64),
+              (-3.2, -0., 0., 5.1, jnp.nan, jnp.inf, -jnp.inf),
+          ),
+      ]
+      for dtype in dtypes
       for value in values
   )
   def test_sign(self, dtype, value):
-    if jtu.test_device_matches(["tpu"]) and dtype == jnp.float64:
-      self.skipTest("float64 is not supported on TPU")
+    if (
+        not jax.config.x64_enabled
+        and dtype in (jnp.uint64, jnp.int64, jnp.float64)
+    ):
+      self.skipTest("64-bit types require x64_enabled")
 
     @functools.partial(
         self.pallas_call,
@@ -692,38 +696,26 @@ def test_sign(self, dtype, value):
     def kernel(x_ref, o_ref):
       o_ref[...] = jnp.sign(x_ref[...])
 
-    with contextlib.ExitStack() as stack:
-      if jnp.dtype(dtype).itemsize == 8:
-        stack.enter_context(config.enable_x64(True))
-
-      x = jnp.full((8, 128,), value, dtype=dtype)
-      out = kernel(x)
-      expected = jnp.sign(x)
-      np.testing.assert_array_equal(out, expected)
+    x = jnp.full((8, 128,), value, dtype=dtype)
+    out = kernel(x)
+    expected = jnp.sign(x)
+    np.testing.assert_array_equal(out, expected)
 
-  @parameterized.product(
-      dtype=[jnp.float32, jnp.float64],
-      value=[-3.2, -1.0, -0.999517, -0.4, 0., 0.72, 0.999517, 1.0, 2.4],
+  @parameterized.parameters(
+      -3.2, -1.0, -0.999517, -0.4, 0., 0.72, 0.999517, 1.0, 2.4
   )
-  def test_erf_inv(self, dtype, value):
-    if jtu.test_device_matches(["tpu"]) and dtype == jnp.float64:
-      self.skipTest("float64 is not supported on TPU")
-
+  def test_erf_inv(self, value):
     @functools.partial(
         self.pallas_call,
-        out_shape=jax.ShapeDtypeStruct((8, 128), dtype),
+        out_shape=jax.ShapeDtypeStruct((8, 128), floatx),
     )
     def kernel(x_ref, o_ref):
       o_ref[...] = lax.erf_inv(x_ref[...])
 
-    with contextlib.ExitStack() as stack:
-      if jnp.dtype(dtype).itemsize == 8:
-        stack.enter_context(config.enable_x64(True))
-
-      x = jnp.full((8, 128), value, dtype=dtype)
-      out = kernel(x)
-      expected = lax.erf_inv(x)
-      np.testing.assert_array_equal(out, expected)
+    x = jnp.full((8, 128), value, dtype=floatx)
+    out = kernel(x)
+    expected = lax.erf_inv(x)
+    np.testing.assert_array_equal(out, expected)
 
 
 class OpsInterpretTest(OpsTest):