[SDAG] Allow folding stack slots into sincos/frexp in more cases (#118117)

This adds a new helper `canFoldStoreIntoLibCallOutputPointers()` to
check that it is safe to fold a store into a node that will expand to a
library call that takes output pointers. This requires checking for two
(independent) properties:

1. The store is not within a CALLSEQ_START..CALLSEQ_END pair
* If it is, the expansion would lead to nested call sequences (which is
invalid)
2. The node does not appear as a predecessor to the store
* If it does, attempting to merge the store into the call would result
in a cycle in the DAG

These two properties are checked as part of the same traversal in
`canFoldStoreIntoLibCallOutputPointers()`

0 files changed, 0 insertions, 0 deletions