Adds a `invoke_quant` higher order operator as proposed [here](https://docs.google.com/document/d/1s2PfJlq6Q1F8l11CkTIC69BW1rEnGEgs6YmBC7hu8rA/edit?tab=t.0).
The primary motivations are
- Unifying scattered reasoning for quant operators throughout the code base
- Easy of pattern matching - see this very large pattern match expression [here](949fdd2997/torch/_inductor/fx_passes/post_grad.py (L390-L426). Compared to the pattern I have in the tests:
```
@register_graph_pattern(
CallFunction(
torch.ops.aten.mm,
CallFunction(
torch.ops.higher_order.invoke_quant,
Ignored(),
Ignored(),
Ignored(),
scheme="nf4",
),
Arg(),
),
pass_dict=test_pass,
)
```
- Ability to specify inductor specific logic, like codegen'ing the operators in lower precision, or forcing fusion to a matmul.
Example graph:
``` Python
===== AFTER POST GRAD =====
/data/users/eellison/pytorch/torch/fx/_lazy_graph_module.py class <lambda>(torch.nn.Module):
def forward(self, arg0_1: "f32[8][1]cpu", arg1_1: "f32[8][1]cpu"):
# File: /data/users/eellison/pytorch/torch/_higher_order_ops/invoke_quant.py:87 in __call__, code: return invoke_quant_tracer(*args, **kwargs, quant_options=self) # type: ignore[call-arg]
repeated_subgraph0 = self.repeated_subgraph0
invoke_quant: "f32[8][1]cpu" = torch.ops.higher_order.invoke_quant(repeated_subgraph0, arg0_1, arg1_1, scheme = 'nf4'); repeated_subgraph0 = arg0_1 = arg1_1 = None
return (invoke_quant,)
class repeated_subgraph0(torch.nn.Module):
def forward(self, arg0_1: "f32[8][1]cpu", arg1_1: "f32[8][1]cpu"):
# File: /data/users/eellison/pytorch/torch/_higher_order_ops/invoke_quant.py:87 in __call__, code: return invoke_quant_tracer(*args, **kwargs, quant_options=self) # type: ignore[call-arg]
mul: "f32[8][1]cpu" = torch.ops.aten.mul.Tensor(arg0_1, arg1_1); arg0_1 = None
add: "f32[8][1]cpu" = torch.ops.aten.add.Tensor(mul, arg1_1); mul = arg1_1 = None
return add
```
The schema for `invoke_quant` is `torch.ops.higher_order.invoke_quant(subgraph, *args, scheme=None)` where the scheme will not always be present.
I wasn't sure exactly how the inductor specific configurations like `codgen_in_low_precision` should be passed through. I didnt want to stuff them all in as kwargs, and I didn't want to have them affect pattern matching. So they will be stored as meta of the node itself. And, following that, I wanted the invocation of the hop to match how it will show up in the graph. So I decided to have it be an object that is then invoked for the tracing.
```
invoke_quant = InvokeQuant(codegen_low_precision=True)
invoke_quant(gn, (x, y), scheme="nf4")
```
Todo - not require the packing of args in a tuple, will do following https://github.com/pytorch/pytorch/pull/139162.
Feedback welcome.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/139102
Approved by: https://github.com/Chillee
92b7e610ab