When two vector transfer ops share a non-entry block argument as an
index (e.g., in a loop with unstructured control flow), calling
`ValueBoundsConstraintSet::areEqual` on those values caused a crash.
The first `populateConstraints` call would insert the block argument
into the constraint set. The second call found it already mapped and
called `getPos`, which hit an assert requiring the value to be either an
OpResult or an entry-block argument.
Fix with two changes:
1. In `insert()`, suppress adding non-entry block arguments to the
worklist. `ValueBoundsOpInterface` cannot derive bounds for such values,
so the worklist push was a no-op and triggered the re-entrant `getPos`
call.
2. Remove the overly conservative assert in `getPos`. Looking up a
previously inserted non-entry block argument is valid; the assert was
preventing legitimate use after the value had already been inserted.
Fixes#119861
Assisted-by: Claude Code
7beba38aa3