[llvm-dev] Bug 20811

De Azevedo Piovezan, Felipe via llvm-dev llvm-dev at lists.llvm.org
Sat Aug 10 10:12:16 PDT 2019

Hi Chouhan,

From a brief inspection of the bug report and the attached IR (lifetime-end.ll), you have a couple of options:

1- You can run `opt lifetime-end.ll -basicaa -gvn -S`. If your change did what it’s supposed to, you should see that `ret i8 %0` was replaced with `ret i8 undef`.

2- The IR attached in the case is in the form of a LIT. You can read more about it here: https://www.llvm.org/docs/TestingGuide.html#writing-new-regression-tests
You would probably commit it as a test with your patch. This test should fail without your change and pass with your change. To run it, you can call `lit lifetime-end.ll` and examine the output of the command.

From: llvm-dev <llvm-dev-bounces at lists.llvm.org> On Behalf Of Shreyansh Chouhan via llvm-dev
Sent: Saturday, August 10, 2019 7:34 AM
To: llvm-dev at lists.llvm.org
Subject: [llvm-dev] Bug 20811

This is my first time contributing to the llvm project, I took up bug #20811 [https://bugs.llvm.org/show_bug.cgi?id=20811]. From my understanding, what I had to do was to assign an undef to a variable if it is loading from a pointer after its lifetime has ended (please correct me if I am wrong.) I would like to ask for help on how could I check if a variable has been assigned undef to verify my changes.

Thanks in advance :)
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