Sym ite prim op (pytorch#20681)

Adds Python op registration, mapping entry, and C++ kernel handling with
tests

Author: psiddh

exir/emit/test/test_emit.py

@@ -2490,6 +2490,46 @@ def forward(self, x):
             self.assertTrue(expected.shape == et_result.shape)
             self.assertTrue(torch.allclose(expected, et_result))
 
+    def test_emit_sym_ite(self) -> None:
+        class SymIteModel(nn.Module):
+            def forward(self, x):
+                n = x.shape[0]
+                m = x.shape[1]
+                cond = n > 5
+                val = torch.sym_ite(cond, n, m)
+                return torch.zeros(val, dtype=x.dtype, device=x.device)
+
+        model = SymIteModel()
+        model.eval()
+        test_inputs = [
+            torch.randn(3, 6),  # n<=5: ite(False,3,6)=6
+            torch.randn(8, 4),  # n>5: ite(True,8,4)=8
+        ]
+        reference_outputs = []
+        with torch.no_grad():
+            for inp in test_inputs:
+                reference_outputs.append(model(inp))
+
+        batch_dim = Dim("batch", min=1, max=20)
+        feat_dim = Dim("feat", min=1, max=20)
+        dynamic_shapes = {"x": {0: batch_dim, 1: feat_dim}}
+        exported_program = torch.export.export(
+            model, (test_inputs[0],), dynamic_shapes=dynamic_shapes
+        )
+
+        edge_program = to_edge(
+            exported_program,
+            compile_config=exir.EdgeCompileConfig(_check_ir_validity=False),
+        )
+        et_program = edge_program.to_executorch()
+        program_buffer = et_program.buffer
+        et_module = _load_for_executorch_from_buffer(program_buffer)
+        for inp, expected in zip(test_inputs, reference_outputs):
+            et_output = et_module.forward([inp])
+            et_result = et_output[0]
+            self.assertTrue(expected.shape == et_result.shape)
+            self.assertTrue(torch.allclose(expected, et_result))
+
     def test_emit_channels_last_constant(self) -> None:
         """Test that channels-last constant tensors are emitted correctly.
 

exir/passes/executorch_prim_ops_registry.py

@@ -134,6 +134,13 @@ def sym_not(a: _SymScalar) -> bool:
     return not a  # pyre-ignore
 
 
+@bind_pattern_to_op(
+    executorch_prims_lib, "sym_ite.Scalar(Scalar b, Scalar t, Scalar f) -> Scalar"
+)
+def sym_ite(b: _SymScalar, t: _SymScalar, f: _SymScalar) -> _SymScalar:
+    return t if b else f  # pyre-ignore
+
+
 _PYTHON_SYM_OPS_TO_EXECUTORCH_SYM_OPS: Dict[Any, OpOverload] = {
     builtins.round: ops.backend.executorch_prim.round.Scalar,
     math.ceil: ops.backend.executorch_prim.ceil.Scalar,
@@ -155,6 +162,7 @@ def sym_not(a: _SymScalar) -> bool:
     torch.sym_max: ops.backend.executorch_prim.sym_max.Scalar,
     torch.sym_min: ops.backend.executorch_prim.sym_min.Scalar,
     torch.sym_not: ops.backend.executorch_prim.sym_not.Scalar,
+    torch.sym_ite: ops.backend.executorch_prim.sym_ite.Scalar,
 }
 
 

kernels/prim_ops/register_prim_ops.cpp

@@ -541,6 +541,48 @@ static Kernel prim_ops[] = {
         }),
 #endif
 
+#if !defined(EXECUTORCH_ENABLE_PRIM_OPS_SELECTIVE_BUILD) || \
+    defined(INCLUDE_EXECUTORCH_PRIM_SYM_ITE_SCALAR)
+    // executorch_prim::sym_ite.Scalar(bool b, Scalar t, Scalar f) -> Scalar
+    Kernel(
+        "executorch_prim::sym_ite.Scalar",
+        [](KernelRuntimeContext& context, Span<EValue*> stack) {
+          ET_KERNEL_CHECK_MSG(
+              context,
+              stack.size() == 4,
+              InvalidProgram,
+              /* void */,
+              "Expected %zu args, got %zu",
+              (size_t)4,
+              stack.size());
+          EValue& b = *stack[0];
+          EValue& out = *stack[3];
+          ET_KERNEL_CHECK_MSG(
+              context,
+              b.isBool(),
+              InvalidType,
+              /* void */,
+              "sym_ite condition must be bool, got %zu",
+              (size_t)b.tag);
+          EValue& selected = b.toBool() ? *stack[1] : *stack[2];
+          if (selected.isInt()) {
+            out = EValue(selected.toInt());
+          } else if (selected.isDouble()) {
+            out = EValue(selected.toDouble());
+          } else if (selected.isBool()) {
+            out = EValue(selected.toBool());
+          } else {
+            ET_KERNEL_CHECK_MSG(
+                context,
+                false,
+                InvalidType,
+                /* void */,
+                "sym_ite value must be int, double, or bool, got %zu",
+                (size_t)selected.tag);
+          }
+        }),
+#endif
+
 #if !defined(EXECUTORCH_ENABLE_PRIM_OPS_SELECTIVE_BUILD) || \
     defined(INCLUDE_EXECUTORCH_PRIM_FLOORDIV_INT)
     // executorch_prim::floordiv.int(int, int) -> int

kernels/prim_ops/test/prim_ops_test.cpp

@@ -42,6 +42,7 @@ TEST_F(RegisterPrimOpsTest, OpRegistered) {
   EXPECT_TRUE(hasOpsFn("executorch_prim::sym_min.Scalar"));
   EXPECT_TRUE(hasOpsFn("executorch_prim::sym_not.Scalar"));
   EXPECT_TRUE(hasOpsFn("executorch_prim::sym_int.Scalar"));
+  EXPECT_TRUE(hasOpsFn("executorch_prim::sym_ite.Scalar"));
 }
 
 TEST_F(RegisterPrimOpsTest, SymSizeReturnsCorrectValue) {
@@ -241,6 +242,46 @@ TEST_F(RegisterPrimOpsTest, SymIntReturnsCorrectValue) {
   EXPECT_EQ(stack[1]->toInt(), 0);
 }
 
+TEST_F(RegisterPrimOpsTest, SymIteReturnsCorrectValue) {
+  EValue values[4];
+  EValue* stack[4];
+  for (size_t i = 0; i < 4; i++) {
+    stack[i] = &values[i];
+  }
+
+  // true branch selects t (int)
+  values[0] = EValue(true);
+  values[1] = EValue((int64_t)42);
+  values[2] = EValue((int64_t)99);
+  values[3] = EValue((int64_t)0);
+  getOpsFn("executorch_prim::sym_ite.Scalar")(context_, Span<EValue*>(stack));
+  EXPECT_EQ(stack[3]->toInt(), 42);
+
+  // false branch selects f (int)
+  values[0] = EValue(false);
+  values[1] = EValue((int64_t)42);
+  values[2] = EValue((int64_t)99);
+  values[3] = EValue((int64_t)0);
+  getOpsFn("executorch_prim::sym_ite.Scalar")(context_, Span<EValue*>(stack));
+  EXPECT_EQ(stack[3]->toInt(), 99);
+
+  // true branch selects t (double)
+  values[0] = EValue(true);
+  values[1] = EValue(3.14);
+  values[2] = EValue(2.72);
+  values[3] = EValue(0.0);
+  getOpsFn("executorch_prim::sym_ite.Scalar")(context_, Span<EValue*>(stack));
+  EXPECT_FLOAT_EQ(stack[3]->toDouble(), 3.14);
+
+  // false branch selects f (bool)
+  values[0] = EValue(false);
+  values[1] = EValue(true);
+  values[2] = EValue(false);
+  values[3] = EValue(false);
+  getOpsFn("executorch_prim::sym_ite.Scalar")(context_, Span<EValue*>(stack));
+  EXPECT_EQ(stack[3]->toBool(), false);
+}
+
 TEST_F(RegisterPrimOpsTest, TestAlgebraOps) {
   EValue values[3];
   int64_t a = 3;