commit 4d91ffb09a8e48844b6460edce58ccba245bced7
author Oleksandr "Alex" Zinenko <git@ozinenko.com> Mon Sep 01 13:52:27 2025 +0200
committer GitHub <noreply@github.com> Mon Sep 01 11:52:27 2025 +0000
tree 6d734064488bc9477a5474d8c127279392feee38
parent c37c680ae6e71f715bd7c540909155061bc44491

[codegen] more consumer fusion (#21521)

Enable consumer fusion to fuse more trailing operations, in particular
to fuse all operations used in layer normalization. The particular
enablement is to allow fusion of consumers of fused operations that are
not the "main" operation into which fusion happens.

This required three modifications:

1. Generate replacement values for any fused operation whose results are
used by operations dominated by the main operation (that will turn into
a loop). This is needed because the consumer fusion finds candidates
based on `insert_slice` operations in the loop that are not produced
unless the replacement values are generated. In the case of layer
normalizaiton, we also need actual replacement values so we can return
them. Spurious values are being cleaned up by canonicalization patterns
in the same pass.
2. Avoid generating replacement values for values used as DPS inits as
those cannot (currently) be fused.
3. Sort consumers to fuse by dominance and first most-dominating
consumer fuse to avoid triangular-use situation that prevents fusion.

This generally makes fusion more aggressive on the consumer side.

Signed-off-by: Alex Zinenko <git@ozinenko.com>