loop-reduce: Add an early bailout to catch extremely large loops.

This introduces a threshold of 200 IV Users, which is very
conservative but should be sufficient to avoid serious compile time
sink or stack overflow. The llvm test-suite with LTO never exceeds 190
users per loop.

The bug doesn't relate to a specific type of loop. Checking in an
arbitrary giant loop as a unit test would be silly.

Fixes rdar://11262507.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@154983 91177308-0d34-0410-b5e6-96231b3b80d8

0 files changed, 0 insertions, 0 deletions