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| author | Stephen Hines <srhines@google.com> | 2014-12-01 14:51:49 -0800 |
|---|---|---|
| committer | Stephen Hines <srhines@google.com> | 2014-12-02 16:08:10 -0800 |
| commit | 37ed9c199ca639565f6ce88105f9e39e898d82d0 (patch) | |
| tree | 8fb36d3910e3ee4c4e1b7422f4f017108efc52f5 /docs/DeveloperPolicy.rst | |
| parent | d2327b22152ced7bc46dc629fc908959e8a52d03 (diff) | |
| download | external_llvm-37ed9c199ca639565f6ce88105f9e39e898d82d0.zip external_llvm-37ed9c199ca639565f6ce88105f9e39e898d82d0.tar.gz external_llvm-37ed9c199ca639565f6ce88105f9e39e898d82d0.tar.bz2 | |
Update aosp/master LLVM for rebase to r222494.
Change-Id: Ic787f5e0124df789bd26f3f24680f45e678eef2d
Diffstat (limited to 'docs/DeveloperPolicy.rst')
| -rw-r--r-- | docs/DeveloperPolicy.rst | 23 |
1 files changed, 23 insertions, 0 deletions
diff --git a/docs/DeveloperPolicy.rst b/docs/DeveloperPolicy.rst index 74a8979..508a04f 100644 --- a/docs/DeveloperPolicy.rst +++ b/docs/DeveloperPolicy.rst @@ -436,6 +436,29 @@ list, development list, or LLVM bug tracker component. If someone sends you a patch privately, encourage them to submit it to the appropriate list first. +IR Backwards Compatibility +-------------------------- + +When the IR format has to be changed, keep in mind that we try to maintain some +backwards compatibility. The rules are intended as a balance between convenience +for llvm users and not imposing a big burden on llvm developers: + +* The textual format is not backwards compatible. We don't change it too often, + but there are no specific promises. + +* The bitcode format produced by a X.Y release will be readable by all following + X.Z releases and the (X+1).0 release. + +* Newer releases can ignore features from older releases, but they cannot + miscompile them. For example, if nsw is ever replaced with something else, + dropping it would be a valid way to upgrade the IR. + +* Debug metadata is special in that it is currently dropped during upgrades. + +* Non-debug metadata is defined to be safe to drop, so a valid way to upgrade + it is to drop it. That is not very user friendly and a bit more effort is + expected, but no promises are made. + .. _copyright-license-patents: Copyright, License, and Patents |