[Quant][PT2E] Enable linear and linear-unary post-op gelu quant recipe for x86 inductor quantizer (#114853)

**Summary**
Add Gelu for linear-unary post-op quantization recipe to x86 inductor quantizer.

**Test plan**
python -m pytest test/quantization/pt2e/test_x86inductor_quantizer.py -k test_linear_unary_gelu
python test/test_quantization.py -k test_linear_unary_with_quantizer_api
Co-authored-by: leslie-fang-intel <leslie.fang@intel.com>
Pull Request resolved: https://github.com/pytorch/pytorch/pull/114853
Approved by: https://github.com/jgong5, https://github.com/leslie-fang-intel, https://github.com/jerryzh168

test/quantization/pt2e/test_x86inductor_quantizer.py

@@ -251,10 +251,13 @@ class TestHelperModules:
             return self.linear(x)
 
     class LinearUnaryModule(torch.nn.Module):
-        def __init__(self, use_bias, postop, inplace_postop) -> None:
+        def __init__(self, use_bias, postop, inplace_postop=False, post_op_algo='none') -> None:
             super().__init__()
             self.linear = nn.Linear(4, 4, bias=use_bias)
-            self.postop = postop(inplace=inplace_postop)
+            if postop == nn.GELU:
+                self.postop = postop(approximate=post_op_algo)
+            else:
+                self.postop = postop(inplace=inplace_postop)
 
         def forward(self, x):
             return self.postop(self.linear(x))
@@ -1010,6 +1013,44 @@ class TestQuantizePT2EX86Inductor(X86InductorQuantTestCase):
                     node_list,
                 )
 
+    @skipIfNoX86
+    def test_linear_unary_gelu(self):
+        """
+        Test pattern of linear with unary post ops (e.g. gelu) with X86InductorQuantizer.
+        """
+        use_bias_list = [True, False]
+        postop = nn.GELU
+        post_op_algorithm = ['none', 'tanh']
+        cases = itertools.product(use_bias_list, post_op_algorithm)
+        with override_quantized_engine("x86"), torch.no_grad():
+            for use_bias, post_op_algo in cases:
+                m = TestHelperModules.LinearUnaryModule(use_bias=use_bias, postop=postop, post_op_algo=post_op_algo).eval()
+                example_inputs = (torch.randn(2, 4),)
+                quantizer = X86InductorQuantizer().set_global(
+                    xiq.get_default_x86_inductor_quantization_config()
+                )
+                node_occurrence = {
+                    # one for input and weight of the conv, one for output for the gelu
+                    torch.ops.quantized_decomposed.quantize_per_tensor.default: 1,
+                    torch.ops.quantized_decomposed.dequantize_per_tensor.default: 1,
+                    # quantize_per_channel for weights are const propagated
+                    torch.ops.quantized_decomposed.quantize_per_channel.default: 0,
+                    torch.ops.quantized_decomposed.dequantize_per_channel.default: 1,
+                }
+                node_list = [
+                    torch.ops.quantized_decomposed.quantize_per_tensor.default,
+                    torch.ops.quantized_decomposed.dequantize_per_tensor.default,
+                    torch.ops.aten.linear.default,
+                    torch.ops.aten.gelu.default,
+                ]
+                self._test_quantizer(
+                    m,
+                    example_inputs,
+                    quantizer,
+                    node_occurrence,
+                    node_list,
+                )
+
     @skipIfTorchDynamo("very slow")
     @skipIfNoX86
     def test_qat_conv2d(self):

torch/ao/quantization/pt2e/prepare.py

@@ -378,11 +378,13 @@ def _maybe_insert_input_observers_for_node(
         numeric_debug_handle = node.meta["numeric_debug_handle"]
         node.meta["numeric_debug_handle"] = {remap_fn(k): v for k, v in numeric_debug_handle.items()}
 
-    # Clone has a memory_format kwarg and zeros_like has a pin_memory kwarg
-    # that persist in exported graph. This is just a work around for these.
+    # Clone has a memory_format kwarg, zeros_like has a pin_memory kwarg, and
+    # gelu has a has an approximate kwarg that persist in exported graph.
+    # This is just a work around for these.
     assert (
         node.target == torch.ops.aten.clone.default or
         node.target == torch.ops.aten.zeros_like.default or
+        node.target == torch.ops.aten.gelu.default or
         len(node.kwargs) == 0
     ), " expecting kwargs for aten op IR to be empty"
 

torch/ao/quantization/quantizer/x86_inductor_quantizer.py

@@ -985,6 +985,7 @@ class X86InductorQuantizer(Quantizer):
             torch.nn.ReLU,
             torch.nn.LeakyReLU,
             torch.nn.Tanh,
+            torch.nn.GELU,
         ]
         fused_partitions: List[tuple] = []
         for postop in postop_list: