[Mosaic] Add support for S32 cross-lane reduction.

tests/pallas/ops_test.py

@@ -526,6 +526,43 @@ def kernel(x_ref, o_ref):
 
     np.testing.assert_allclose(result[0, 0], reduction_op(x), atol=1e-5)
 
+  @parameterized.named_parameters(
+      ("sum", jnp.sum, (32, 256)),
+      ("max", jnp.max, (32, 256)),
+      ("min", jnp.min, (32, 256)),
+      ("sum_irregular", jnp.sum, (31, 300)),
+      ("max_irregular", jnp.max, (31, 300)),
+      ("min_irregular", jnp.min, (31, 300)),
+  )
+  def test_reduce_int32(self, reduction_op, input_shape):
+    if jtu.test_device_matches(["gpu"]):
+      self.skipTest("TODO: error on GPU")
+    # TODO(b/395579834): Remove this skip later.
+    if not jtu.if_cloud_tpu_at_least(2025, 9, 1):
+      self.skipTest("Requires libtpu built after 2025-09-01")
+
+    def kernel(x_ref, o_ref):
+      o_ref[0, 0] = reduction_op(x_ref[...])
+
+    x = jax.random.randint(
+        jax.random.key(0),
+        shape=input_shape,
+        minval=-100,
+        maxval=100,
+        dtype=jnp.int32,
+    )
+    result = self.pallas_call(
+        kernel,
+        in_specs=[
+            pl.BlockSpec(input_shape, lambda *_: (0, 0)),
+        ],
+        out_specs=pl.BlockSpec((1, 1), memory_space=smem_on_tpu()),
+        out_shape=jax.ShapeDtypeStruct([1, 1], intx),
+        grid=(1,),
+    )(x)
+
+    np.testing.assert_allclose(result[0, 0], reduction_op(x), atol=1e-5)
+
   # TODO(sharadmv): test rank < 2, size < 2
   @hp.given(select_n_strategy(max_cases=2, min_rank=2, max_rank=4,
                               min_size_exp=1))

tests/pallas/tpu_ops_test.py

@@ -305,12 +305,13 @@ def kernel(x_ref, mask_ref, o_ref):
       reduce_func = [jnp.sum, jnp.max, jnp.min]
   )
   def test_reduction(self, dtype, axis, reduce_func):
-    if dtype == jnp.int32:
-      if axis == 2:
-        self.skipTest("Int32 reduction on minor is not supported.")
-    # TODO(b/384127570): fix bfloat16 reduction.
-    if dtype == jnp.bfloat16 and reduce_func != jnp.sum:
-      self.skipTest("b/384127570")
+    # TODO(b/395579834): Remove this skip later.
+    if (
+        dtype == jnp.int32
+        and axis == 2
+        and not jtu.if_cloud_tpu_at_least(2025, 9, 1)
+    ):
+      self.skipTest("Requires libtpu built after 2025-09-01")
     in_shape = (2, 16, 128)
     out_shape = list(in_shape)
     out_shape[axis] = 1

tests/pallas/tpu_pallas_test.py

@@ -1967,9 +1967,13 @@ def kernel(x, out):
   def test_replicated_broadcast_reduction(
       self, m, replicated, reduced_dims, dty, reduce_func
   ):
-    if dty == jnp.int32 and 1 in reduced_dims:
-      # TODO(b/395579834): Remove this skip once we implement this.
-      self.skipTest('int32 reduction on last dimension not supported')
+    # TODO(b/395579834): Remove this skip later.
+    if (
+        dty == jnp.int32
+        and 1 in reduced_dims
+        and is_cloud_tpu_older_than(2025, 9, 1)
+    ):
+      self.skipTest('Requires libtpu built after 2025-09-01')
     if not jtu.is_device_tpu_at_least(4) and len(replicated) == 2:
       self.skipTest(
           'Brodcast in both sublanes and lanes not supported on this hardware'