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| author | Philip Reames <listmail@philipreames.com> | 2019-08-05 22:34:59 +0000 |
|---|---|---|
| committer | Philip Reames <listmail@philipreames.com> | 2019-08-05 22:34:59 +0000 |
| commit | e39e79358fcdd5d8ad809defaa821f0bbfa809a5 (patch) | |
| tree | fbfa92766ea0b0750828bc803624f4d7a043901f | |
| parent | f708f0a2430f3a50b8836f4bd5510169dea359eb (diff) | |
| download | bcm5719-llvm-e39e79358fcdd5d8ad809defaa821f0bbfa809a5.tar.gz bcm5719-llvm-e39e79358fcdd5d8ad809defaa821f0bbfa809a5.zip | |
Add a note to the release not about a potentially breaking optimization
This has come up twice already (once in pr42763 and once in the commit thread), so give warning of a new way in which UB can result in unexpected program behavior.
llvm-svn: 367941
| -rw-r--r-- | llvm/docs/ReleaseNotes.rst | 13 |
1 files changed, 13 insertions, 0 deletions
diff --git a/llvm/docs/ReleaseNotes.rst b/llvm/docs/ReleaseNotes.rst index 7b7972f3187..494efd4a65e 100644 --- a/llvm/docs/ReleaseNotes.rst +++ b/llvm/docs/ReleaseNotes.rst @@ -50,6 +50,19 @@ Non-comprehensive list of changes in this release Makes programs 10x faster by doing Special New Thing. +Noteworthy optimizations +------------------------ + +* LLVM will now remove stores to constant memory (since this is a + contradiction) under the assumption the code in question must be dead. This + has proven to be problematic for some C/C++ code bases which expect to be + able to cast away 'const'. This is (and has always been) undefined + behavior, but up until now had not been actively utilized for optimization + purposes in this exact way. For more information, please see: + `bug 42763 <https://bugs.llvm.org/show_bug.cgi?id=42763>_` and + `post commit discussion <http://lists.llvm.org/pipermail/llvm-commits/Week-of-Mon-20190422/646945.html>_`. + + Changes to the LLVM IR ---------------------- |
