[llvm-bugs] [Bug 33527] New: Add a flag to force the llvm::Linker to import of Global Intrinsic Variables
llvm-bugs at lists.llvm.org
Tue Jun 20 08:53:32 PDT 2017
Bug ID: 33527
Summary: Add a flag to force the llvm::Linker to import of
Global Intrinsic Variables
Assignee: unassignedbugs at nondot.org
Reporter: benoit.belley at autodesk.com
CC: llvm-bugs at lists.llvm.org
We are suggesting adding a flag to the llvm::Linker to force to import global
The usage scenario for using this flag goes as follows:
1. A front-end generates an LLVM module.
2. A small runtime support library is linked-in. The runtime
library is distributed as bitcode. It is generated using "clang++
-emit-llvm' and 'llvm-link'. This allows LTO to kick-in and
functions from the runtime support library become candidates for
inlining. This is the desired effect.
3. The resulting LLVM module is compiled and dynamically loaded.
The issue is with the Linker::LinkOnlyNeeded flag. Using it has a huge
positive impact on link and compilation time :-). But, it causes the
@llvm.global_ctors and @llvm.global_dtors references from the
linked-in modules to be discarded :-(. AFAICT, the Linker code assumes
ThinLTO when the LinkOnlyNeeded flags is specified, and full-LTO
To resolve this, we are suggesting adding an extra flag, namely
Linker::ImportGlobalIntrinsicVariables to specify that the global intrinsic
variables of the source module should be imported into the destination module.
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