sanjoy added a comment.
I don't think this is an infinite loop (Piotr, can you please verify
this?), it is probably an O(n!) recursion where n == number of the
assumptions.
ScalarEvolution::isImpliedCond already guards for infinite loops via
MarkPendingLoopPredicate. However, if you have
assume
> Both tests are protected by there being exactly one latch in the loop (we
> exit early if there's not one latch). I'm not sure what makes the
> LoopContinuePredicate check safer?
You can have a loop with a single latch but an arbitrary number of
assumes (= n). In such a loop, you'll still end u
Prazek added a comment.
I used "hanging out" in the meaning of being very slow, not sure if it is right
word for it.
http://reviews.llvm.org/D12719
___
cfe-commits mailing list
cfe-commits@lists.llvm.org
http://lists.llvm.org/cgi-bin/mailman/listin
Prazek added a comment.
I checked it, it is of course not infinite. I am not sure about n! in case of
assumes. I having 10 or 20 assumes will not make it slow. @rsmith was helping
me with it, and he thinks that for assumes it is O(n^2), because results are
memorized.
So it this case, 1000 assu
On 8 September 2015 at 20:27, Sanjoy Das
wrote:
> sanjoy added a comment.
>
> I don't think this is an infinite loop (Piotr, can you please verify
> this?), it is probably an O(n!) recursion where n == number of the
> assumptions.
>
> ScalarEvolution::isImpliedCond already guards for infinite loo
nlewycky added inline comments.
Comment at: lib/Analysis/ScalarEvolution.cpp:6980
@@ -6991,1 +6979,3 @@
+ // Check conditions due to any @llvm.assume intrinsics.
+ for (auto &AssumeVH : AC.assumptions()) {
Prazek wrote:
> nlewycky wrote:
> > What is it about t
Prazek added inline comments.
Comment at: lib/Analysis/ScalarEvolution.cpp:6980
@@ -6991,1 +6979,3 @@
+ // Check conditions due to any @llvm.assume intrinsics.
+ for (auto &AssumeVH : AC.assumptions()) {
nlewycky wrote:
> What is it about this check which is a
nlewycky added inline comments.
Comment at: lib/Analysis/ScalarEvolution.cpp:6980
@@ -6991,1 +6979,3 @@
+ // Check conditions due to any @llvm.assume intrinsics.
+ for (auto &AssumeVH : AC.assumptions()) {
What is it about this check which is a problem? Or put
Prazek created this revision.
Prazek added reviewers: rsmith, nlewycky.
Prazek added a subscriber: cfe-commits.
Herald added a subscriber: sanjoy.
http://reviews.llvm.org/D12719
Files:
lib/Analysis/ScalarEvolution.cpp
test/Analysis/ScalarEvolution/avoid-assume-hang.ll
Index: test/Analysis/Sc
