[llvm-dev] llvm-link: why link '@llvm.global_ctors' into dest file even it's not used in dest file?
Ronan KERYELL via llvm-dev
llvm-dev at lists.llvm.org
Thu Jan 3 20:38:10 PST 2019
>>>>> On Thu, 3 Jan 2019 15:15:15 -0800, Mehdi AMINI via llvm-dev <llvm-dev at lists.llvm.org> said:
Mehdi> On Wed, Jan 2, 2019 at 2:52 PM Fangqing Du via llvm-dev <llvm-dev at lists.llvm.org> wrote:
> Hi all,
> Recently I do some jobs based on llvm-link tool. I wonder
> why link '@llvm.global_ctors' into dest file, even it's not
> used in dest file?
Mehdi> This is a "magic" global variable:
Mehdi> It is implicitly used by the loader of the program before
Mehdi> entering main().
Mehdi> Think about how a C++ global variable constructor can
Mehdi> register itself and the "destination file" you're mentionning
Mehdi> can query this registry.
But it is true that the dead-code elimination phases could remove it
when not used...
> And how can I remove it?
Mehdi> Like other global variables? You need to transform the module
Mehdi> yourself before linking it (if you believe it is safe to do
In our SYCL compiler I wrote a pass to remove it:
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