[PATCH] Use loop unrolling pragma metadata in the loop unroller

[Mark Heffernan]

================
Comment at: lib/Transforms/Scalar/LoopUnrollPass.cpp:58
@@ -50,1 +57,3 @@
+static const unsigned PragmaFullUnrollCountLimit = 1024;
+
 namespace {
----------------
Philip Reames wrote:
> a) I would choose a slightly higher value.  The reason for the limit is mostly to avoid absolutely insane behaviour.   i.e. 100k might be a good one
> b) Does the frontend enforce any type of limit?
> c) Might be worth making this an command line option
> 
> None of these are must change, use your judgement.
(Looks like phabricator never sent out your comment at least to me, sigh)

Anyway, to answer your questions/comments.  The frontend does not enforce a limit other than that the count has to be a positive value.  The patch got reverted because it was a suspect in a build breakage.  The second attempt includes making it a cl opt as you suggest and uses a size threshold rather than a count threshold.  See http://reviews.llvm.org/D4147.

http://reviews.llvm.org/D4090