Lunderberg commented on code in PR #16966:
URL: https://github.com/apache/tvm/pull/16966#discussion_r1598715370
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src/tir/transforms/vectorize_loop.cc:
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@@ -72,6 +72,126 @@ inline PrimExpr BroadcastTo(PrimExpr e, int lanes, bool
is_scalable) {
return Broadcast(e, CreateNewLanes(is_scalable, lanes));
}
+bool EnableBufferLevelPredication() {
Review Comment:
To my knowledge, there isn't a general utility that would provide it, though
I definitely agree on its usefulness.
There's currently a couple similar utilities, such as
[`IRMutatorWithAnalyzer`](https://github.com/apache/tvm/blob/main/src/arith/ir_mutator_with_analyzer.h#L45)
and
[`IRVisitorWithAnalyzer`](https://github.com/apache/tvm/blob/main/src/arith/ir_visitor_with_analyzer.h#L35),
which allow context-dependent algebraic simplifications. The easiest way to
implement such a utility for target-aware simplifications would be to extract
out the context-dependent target tracking from an existing visitor/mutator
(e.g.
[here](https://github.com/apache/tvm/blob/main/src/tir/transforms/lower_device_kernel_launch.cc#L65),
used in the `LowerDeviceKernelLaunch` transform) into a `IRVisitorWithTarget`
and `IRMutatorWithTarget`, which is then subclassed again by each transform
that requires it.
For long-term maintainability, I like your suggestion of mixins much more
than the subclasses, because they could be composed together much more easily.
Implemented with subclasses, a hypothetical transform that requires both the
context-dependent target and context-dependent algebraic simplifications would
have incorrect behavior from multiple inheritance, and would need to
re-implement one or the other functionalities.
Unfortunately, I don't think the current `tir::StmtVisitor` API could be
used to support mixins, either through multiple inheritance or through
composition. The main issue is that the implementable virtual functions (e.g.
`tir::StmtVisitor::VisitStmt_(const tir::ForNode*)`) aren't granular enough.
In order to compose separate transforms that provide context-dependent
information, it would require separate virtual functions for pre-visit and
post-visit. I've toyed around with different variations of the TIR stmt/expr
visitor/mutator implementations, but haven't had the time to make anything
PR-able.
TL;DR: It doesn't currently exist, would be very useful to have, and a
subclass would be sufficient for this PR, though long-term maintainability
concerns may appear at some point in the future.
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