[llvm] r254956 - Remove useless hack that avoids calling LLVMLinkInInterpreter()

[Mehdi Amini via llvm-commits]

> On Dec 7, 2015, at 2:40 PM, David Majnemer <david.majnemer at gmail.com> wrote:
> 
> 
> 
> On Mon, Dec 7, 2015 at 5:32 PM, David Blaikie via llvm-commits <llvm-commits at lists.llvm.org <mailto:llvm-commits at lists.llvm.org>> wrote:
> 
> 
> On Mon, Dec 7, 2015 at 2:27 PM, Mehdi Amini via llvm-commits <llvm-commits at lists.llvm.org <mailto:llvm-commits at lists.llvm.org>> wrote:
> Author: mehdi_amini
> Date: Mon Dec  7 16:27:19 2015
> New Revision: 254956
> 
> URL: http://llvm.org/viewvc/llvm-project?rev=254956&view=rev <http://llvm.org/viewvc/llvm-project?rev=254956&view=rev>
> Log:
> Remove useless hack that avoids calling LLVMLinkInInterpreter()
> 
> This is supposed to force-link the Interpreter, by inserting a dead
> call to LLVMLinkInInterpreter().
> Since it is actually an empty function, there is no reason for the
> call to be dead.
> 
> From: Mehdi Amini <mehdi.amini at apple.com <mailto:mehdi.amini at apple.com>>
> 
> Modified:
>     llvm/trunk/include/llvm/ExecutionEngine/Interpreter.h
> 
> Modified: llvm/trunk/include/llvm/ExecutionEngine/Interpreter.h
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/ExecutionEngine/Interpreter.h?rev=254956&r1=254955&r2=254956&view=diff <http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/ExecutionEngine/Interpreter.h?rev=254956&r1=254955&r2=254956&view=diff>
> ==============================================================================
> --- llvm/trunk/include/llvm/ExecutionEngine/Interpreter.h (original)
> +++ llvm/trunk/include/llvm/ExecutionEngine/Interpreter.h Mon Dec  7 16:27:19 2015
> @@ -16,22 +16,12 @@
>  #define LLVM_EXECUTIONENGINE_INTERPRETER_H
> 
>  #include "llvm/ExecutionEngine/ExecutionEngine.h"
> -#include <cstdlib>
> 
>  extern "C" void LLVMLinkInInterpreter();
> 
>  namespace {
>    struct ForceInterpreterLinking {
> -    ForceInterpreterLinking() {
> -      // We must reference the interpreter in such a way that compilers will not
> -      // delete it all as dead code, even with whole program optimization,
> -      // yet is effectively a NO-OP. As the compiler isn't smart enough
> -      // to know that getenv() never returns -1, this will do the job.
> -      if (std::getenv("bar") != (char*) -1)
> -        return;
> -
> -      LLVMLinkInInterpreter();
> -    }
> +    ForceInterpreterLinking() { LLVMLinkInInterpreter(); }
>    } ForceInterpreterLinking;
> 
> Not sure if you want to, but could possibly simplify this further with something like:
> 
> int i = (LLVMLinkInInterpreter(), 1);
> 
> Maybe? Not sure if that's any better, stylistically, etc.
> 
> Personally, I'd find that more surprising than a global ctor.

Actually I’d rather eliminate the global ctor entirely (it will be currently emitted anywhere this header is included) and have the call to `LLVMLinkInInterpreter()` to be inserted appropriately on the required path. 
The “client" of the header being responsible to choose how to call it (global ctor or other).

— 
Mehdi


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