[DFAJumpThreading] Add MaxOuterUseBlocks threshold (#163428)

For every threadable path `B1 -> B2 -> ... -> Bn`, we need to insert phi
nodes into every unduplicated successor of `Bi` if there are outer uses
of duplicated definitions in `B_i`. To prevent the booming of phi nodes,
this patch adds a threshold for the maximum number of unduplicated
successors that may contain outer uses. This threshold makes sense
especially when multi-target branches like switch/indirectbr/callbr are
duplicated.

Note that the O3 statistics in llvm-test-suite are not influenced.

0 files changed, 0 insertions, 0 deletions