llvm-project/llvm/lib/Linker
Duncan P. N. Exon Smith 09d84addb7 Don't upgrade global constructors when reading bitcode
An optional third field was added to `llvm.global_ctors` (and
`llvm.global_dtors`) in r209015.  Most of the code has been changed to
deal with both versions of the variables.  Users of the C API might
create either version, the helper functions in LLVM create the two-field
version, and clang now creates the three-field version.

However, the BitcodeReader was changed to always upgrade to the
three-field version.  This created an unnecessary inconsistency in the
IR before/after serializing to bitcode.

This commit resolves the inconsistency by making the third field truly
optional (and not upgrading in the bitcode reader).  Since `llvm-link`
was relying on this upgrade code, rather than deleting it I've moved it
into `ModuleLinker`, where it upgrades these arrays as necessary to
resolve inconsistencies between modules.

The ideal resolution would be to remove the 2-field version and make the
third field required.  I filed PR20506 to track that.

I changed `test/Bitcode/upgrade-global-ctors.ll` to a negative test and
duplicated the `llvm-link` check in `test/Linker/global_ctors.ll` to
check both upgrade directions.

Since I came across this as part of PR5680 (serializing use-list order),
I've also added the missing `verify-uselistorder` RUN line to
`test/Bitcode/metadata-2.ll`.

llvm-svn: 215457
2014-08-12 16:46:37 +00:00
..
CMakeLists.txt Now that Linker.cpp is almost empty, merge it into LinkModules.cpp. 2013-05-04 03:48:37 +00:00
LLVMBuild.txt [Linker] Kill Linker::LoadObject which is dead, and drop the BitReader dependency again. 2013-01-18 19:37:11 +00:00
LinkModules.cpp Don't upgrade global constructors when reading bitcode 2014-08-12 16:46:37 +00:00
Makefile