Last we looked at this and couldn't come up with a reason to change
it, but with a pragma for full loop unrolling we bypass every other
loop unroll and then fail to fully unroll a loop when the pragma is set.
Move the OnlyWhenForced out of the check and into the initialization
of the full unroll pass in the new pass manager. This doesn't show up
with the old pass manager.
Add a new option to opt so that we can turn off loop unrolling
manually since this is a difference between clang and opt.
Tested with check-clang and check-llvm.
we will unroll loops. Also comment a few occasions where we need to
know whether or not we're forcing the unwinder or not.
The default before and after this patch is for LoopUnroll to be enabled,
and for it to use a cost model to determine whether to unroll the loop
(`OnlyWhenForced = false`). Before this patch, disabling loop unroll
would not run the LoopUnroll pass. After this patch, the LoopUnroll pass
is being run, but it restricts unrolling to only the loops marked by a
pragma (`OnlyWhenForced = true`).
In addition, this patch disables the UnrollAndJam pass when disabling unrolling.
Testcase is in clang because it's controlling how the loop optimizer
is being set up and there's no other way to trigger the behavior.
llvm-svn: 374838
Eric Christopher