[PATCH] D23680: [ThinLTO] Emit files for distributed builds for all modules

Peter Collingbourne via llvm-commits llvm-commits at lists.llvm.org
Tue Sep 20 11:04:57 PDT 2016


pcc added inline comments.

================
Comment at: tools/gold/gold-plugin.cpp:755
@@ -754,1 +754,3 @@
 
+// Write empty files that may be expected by a distributed build
+// system when invoked with thinlto_index_only. This is invoked when
----------------
tejohnson wrote:
> mehdi_amini wrote:
> > tejohnson wrote:
> > > pcc wrote:
> > > > I am not sure if this is needed, but even if it is, can't this be done inside lib/LTO?
> > > This is needed because the distributed build system (in this case Bazel) wants to check that its expected outputs were generated. It doesn't know what the linker decided to include in the final link or not. This was a regression from the earlier behavior before we moved to the new LTO API.
> > > 
> > > My earlier version of the patch had this fix in lib/LTO, but Mehdi expressed a preference (in an offline discussion) to move this into the client.
> > Right: it seems "client specific" as it is a constraint that comes from Bazel.
> Although note that Bazel is independent of gold. It just happens that we build with using the gold linker and the Bazel distributed build system.
When you say "It doesn't know what the linker decided to include" are you referring to which archive members the linker chose?

So the regression is that the distributed build is missing non-ThinLTO objects from archives, and the fix is to create empty .thinlto.bc files to cause the build system to include the non-ThinLTO objects in the final link?

Or am I misunderstanding?


https://reviews.llvm.org/D23680





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