[PowerPC] Check hot loop exit edge in PPCCTRLoops
PPCCTRLoops transform loops using mtctr/bdnz instructions if loop trip count is known and big enough to compensate for the cost of mtctr.
But if there is a loop exit edge which is known to be frequently taken (by builtin_expect or by PGO), we should not transform the loop to avoid the cost of mtctr instruction. Here is an example of a loop with hot exit edge:
for (unsigned i = 0; i < TripCount; i++) {
// do something
if (__builtin_expect(check(), 1))
break;
// do something
}
Differential Revision: https://reviews.llvm.org/D42637
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@324229 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed