ciflow/torchtitan/183334: Update on "Fix triton eager_input_vals propagation"

Fixes #181735

The old eager_input_vals propagation in replace_by_example assumed the

eager trace and the val trace would produce replacement graphs with the

same number of nodes. That is not true for

triton_kernel_wrapper_functional when the decomposition clones an

as_strided view with a dynamic size-1 leading dimension.

Keep the existing generic eager_input_vals propagation for the

auto_functionalized paths, but make replace_by_example return the

inserted replacement nodes so decompositions can attach metadata

explicitly when needed. Use that only for

triton_kernel_wrapper_functional, propagating eager_input_vals directly

to the inserted triton_kernel_wrapper_mutation node.

We were not able to come up with a failing auto_functionalized repro

before this change, and we do not understand that case well enough to

justify touching it here, so this patch intentionally leaves that path

alone.

Also add a regression test for the Triton fail-before case and a direct

test for the replace_by_example return value.

Test Plan:

python test/inductor/test_needs_exact_strides.py -v

python test/inductor/test_pattern_matcher.py -v -k replace_by_example

python test/inductor/test_triton_kernels.py -v

AI-Assisted: Authored with Claude and Codex.

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