[LLVMdev] How to prevent duplication of function calls?

[Dmitry Denisenko]

Hello,

Is it possible to prevent duplication of call sites for specific functions (while still maintaining -O3 optimization level)? For example, the following C code:

------------------
if (cond1) a=2;
llvm.memory.barrier(...);
------------------

is turned by clang with -O2 into something like this:

------------------
if (cond1)
          a=2;
          llvm.memory.barrier(...);
else
          llvm.memory.barrier(...);
------------------

We're doing C to HDL compilation with LLVM. Having multiple locations that call llvm.memory.barrier(...) would cause complications to generated hardware.

So far, I can think of only two solutions. One is to add support for something like "noclone" attribute and update all optimizations to obey it. The other is to re-merge the calls as a final pass. Any better ideas?

Thank you,
Dmitry


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