llvm-project/llvm/lib/Linker
Duncan P. N. Exon Smith 4fb46cb818 Linker: Move distinct MDNodes instead of cloning
Instead of cloning distinct `MDNode`s when linking in a module, just
move them over.  The module linker destroys the source module, so the
old node would otherwise just be leaked on the context.  Create the new
node in place.  This also reduces the number of cloned uniqued nodes
(since it's less likely their operands have changed).

This mapping strategy is only correct when we're discarding the source,
so the linker turns it on via a ValueMapper flag, `RF_MoveDistinctMDs`.

There's nothing observable in terms of `llvm-link` output here: the
linked module should be semantically identical.

I'll be adding more 'distinct' nodes to the debug info metadata graph in
order to break uniquing cycles, so the benefits of this will partly come
in future commits.  However, we should get some gains immediately, since
we have a fair number of 'distinct' `DILocation`s being linked in.

llvm-svn: 243883
2015-08-03 17:09:38 +00:00
..
CMakeLists.txt modules: Add explicit dependency on intrinsics_gen 2015-06-16 00:44:12 +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 Linker: Move distinct MDNodes instead of cloning 2015-08-03 17:09:38 +00:00
Makefile