5 Commits

Author SHA1 Message Date
Sanjay Patel
f6e615cc84 [ValueTracking] emit a remark when we detect a conflicting assumption (PR31809)
This is a follow-up to D29395 where we try to be good citizens and let the user know that
we've probably gone off the rails.

This should allow us to resolve:
https://llvm.org/bugs/show_bug.cgi?id=31809

Differential Revision: https://reviews.llvm.org/D29404


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@294208 91177308-0d34-0410-b5e6-96231b3b80d8
2017-02-06 18:26:06 +00:00
Sanjay Patel
24d35c93d6 [ValueTracking] remove a FIXME for something we don't want to do; NFC
The comment was added with:
https://reviews.llvm.org/rL293773
...but there would be a cost to implement this and possibly no payoff.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@293823 91177308-0d34-0410-b5e6-96231b3b80d8
2017-02-01 22:27:34 +00:00
Sanjay Patel
ab1df8f850 [ValueTracking] avoid crashing from bad assumptions (PR31809)
A program may contain llvm.assume info that disagrees with other analysis. 
This may be caused by UB in the program, so we must not crash because of that.

As noted in the code comments:
https://llvm.org/bugs/show_bug.cgi?id=31809
...we can do better, but this at least avoids the assert/crash in the bug report.

Differential Revision: https://reviews.llvm.org/D29395


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@293773 91177308-0d34-0410-b5e6-96231b3b80d8
2017-02-01 15:41:32 +00:00
Sanjay Patel
89e202e5fa [InstSimplify] regenerate checks using a script
I didn't notice any significant changes in the actual checks here;
all of these tests already used FileCheck, so a script can batch
update them in one shot.

This commit is just to show the value of automating this process: 
We have uniform formatting as opposed to a mish-mash of check
structure that changes based on individual prefs and the current
fashion. This makes it simpler to update when we find a bug or
make an enhancement.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@264457 91177308-0d34-0410-b5e6-96231b3b80d8
2016-03-25 20:12:25 +00:00
Hal Finkel
8ef7b17dfc Add @llvm.assume, lowering, and some basic properties
This is the first commit in a series that add an @llvm.assume intrinsic which
can be used to provide the optimizer with a condition it may assume to be true
(when the control flow would hit the intrinsic call). Some basic properties are added here:

 - llvm.invariant(true) is dead.
 - llvm.invariant(false) is unreachable (this directly corresponds to the
   documented behavior of MSVC's __assume(0)), so is llvm.invariant(undef).

The intrinsic is tagged as writing arbitrarily, in order to maintain control
dependencies. BasicAA has been updated, however, to return NoModRef for any
particular location-based query so that we don't unnecessarily block code
motion.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@213973 91177308-0d34-0410-b5e6-96231b3b80d8
2014-07-25 21:13:35 +00:00