Max Kazantsev 8f8f2fa4dd [SCEV] Make exact taken count calculation more optimistic ...

Currently, `getExact` fails if it sees two exit counts in different blocks. There is
no solid reason to do so, given that we only calculate exact non-taken count
for exiting blocks that dominate latch. Using this fact, we can simply take min
out of all exits of all blocks to get the exact taken count.

This patch makes the calculation more optimistic with enforcing our assumption
with asserts. It allows us to calculate exact backedge taken count in trivial loops
like

  for (int i = 0; i < 100; i++) {
    if (i > 50) break;
    . . .
  }

Differential Revision: https://reviews.llvm.org/D44676
Reviewed By: fhahn


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@328611 91177308-0d34-0410-b5e6-96231b3b80d8

2018-03-27 07:30:38 +00:00

..

llvm

[SCEV] Make exact taken count calculation more optimistic

2018-03-27 07:30:38 +00:00

llvm-c

Reapply Support layering fixes.

2018-03-21 17:31:49 +00:00