[inductor] Introduce CSEVariable type and use it to track if Triton variables are scalar (#88347)
This fixes https://github.com/pytorch/torchdynamo/issues/1515
To fix it, we need to keep track of whether a Triton variable is a scalar (so we can not use a mask when doing indirect loads through them). This requires a way of annotating variable names generated by CSE with properties.
So now CSE will use CSEVariable class to keep track of variables and let backends subclass it so they can annotate them with whatever information they want. TritonCSEVariable is such a subclass that track the `is_scalar` property.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/88347
Approved by: https://github.com/jgong5, https://github.com/ngimel
