[llvm] 8608650 - [docs] Frotend perf tips: mention poison vs undef and noundef attribute

[Nuno Lopes via llvm-commits]

Author: Nuno Lopes
Date: 2022-02-20T11:59:04Z
New Revision: 8608650a7652fa154de493c760374ea19fa75cc1

URL: https://github.com/llvm/llvm-project/commit/8608650a7652fa154de493c760374ea19fa75cc1
DIFF: https://github.com/llvm/llvm-project/commit/8608650a7652fa154de493c760374ea19fa75cc1.diff

LOG: [docs] Frotend perf tips: mention poison vs undef and noundef attribute

Added: 
    

Modified: 
    llvm/docs/Frontend/PerformanceTips.rst

Removed: 
    


################################################################################
diff  --git a/llvm/docs/Frontend/PerformanceTips.rst b/llvm/docs/Frontend/PerformanceTips.rst
index 5889329e25fc..e4a3bc034b47 100644
--- a/llvm/docs/Frontend/PerformanceTips.rst
+++ b/llvm/docs/Frontend/PerformanceTips.rst
@@ -170,8 +170,7 @@ Other Things to Consider
    comparison type.  The GVN pass *will* optimize redundant equalities even if
    the type of comparison is inverted, but GVN only runs late in the pipeline.
    As a result, you may miss the opportunity to run other important
-   optimizations.  Improvements to EarlyCSE to remove this issue are tracked in
-   Bug 23333.
+   optimizations.
 
 #. Avoid using arithmetic intrinsics unless you are *required* by your source
    language specification to emit a particular code sequence.  The optimizer
@@ -227,6 +226,12 @@ Describing Aliasing Properties
 
 #. Use inbounds on geps.  This can help to disambiguate some aliasing queries.
 
+Undefined Values
+^^^^^^^^^^^^^^^^
+
+#. Use poison values instead of undef values whenever possible.
+
+#. Tag function attributes with the noundef attribute whenever possible.
 
 Modeling Memory Effects
 ^^^^^^^^^^^^^^^^^^^^^^^^
@@ -276,8 +281,8 @@ relatively common and are generally well received by the community.  You will
 need to ensure that your proposal is sufficiently general so that it benefits
 others if you wish to contribute it upstream.
 
-You should also consider describing the problem you're facing on `llvm-dev
-<http://lists.llvm.org/mailman/listinfo/llvm-dev>`_ and asking for advice.
+You should also consider describing the problem you're facing on `Discourse
+<https://discourse.llvm.org>`_ and asking for advice.
 It's entirely possible someone has encountered your problem before and can
 give good advice.  If there are multiple interested parties, that also
 increases the chances that a metadata extension would be well received by the
@@ -290,8 +295,7 @@ If you run across a case that you feel deserves to be covered here, please send
 a patch to `llvm-commits
 <http://lists.llvm.org/mailman/listinfo/llvm-commits>`_ for review.
 
-If you have questions on these items, please direct them to `llvm-dev
-<http://lists.llvm.org/mailman/listinfo/llvm-dev>`_.  The more relevant
+If you have questions on these items, please ask them on `Discourse
+<https://discourse.llvm.org>`_.  The more relevant
 context you are able to give to your question, the more likely it is to be
 answered.
-