Some traps of LLVM Mcjit

Some traps of LLVM Mcjit

Self-handling Baidu space

Recently, the old version of LLVM JIT transformation to Mcjit, encountered some problems

The first is how to start Mcjit,

Original call Initializenativetarget (); Place, add

Initializenativetargetasmprinter ();

Initializenativetargetasmparser ();

Otherwise it will error: Target does not support MC emission!?

When creating execution engine

Enginebuilder EB (M);

EB. Setusemcjit (true);

(If you are on a Windows system) find the Llvm::sys::getprocesstriple function in the LLVM source code,

The last sentence should read

#ifdef LLVM_ON_WIN32

return Pt.str () + "-elf";

#else

return Pt.str ();

#endif

Otherwise error: Incompatible object format!

You must then Theexecutionengine->finalizeobject () after you join the module. Otherwise, address redirection doesn't work.

In the end, Mcjit's execution engine, whether you have addglobalmapping or not, will not find the global symbol error.

You need to specify a memorymanager when you create the engine

Eb.setmcjitmemorymanager (New Helpingmemorymanager (this));

Helpingmemorymanager class please refer to

Https://github.com/llvm-mirror/llvm/blob/master/examples/Kaleidoscope/MCJIT/cached/toy.cpp

The official blog about the use of Mcjit:

? http://project1439.rssing.com/chan-6400099/all_p2.html

The Helpingmemorymanager class is equivalent to providing a link to a symbolic and absolute address, instead of the previous addglobalmapping

It is important to note that in the Helpingmemorymanager code that is given by the authorities, the getpointertonamedfunction is required to be overloaded. Probably a version of the problem, I used the LLVM 3.4.2 need to overload is getsymboladdress, the source code has comments:

This function is deprecated-memory managers to being used with

Mcjit or Runtimedyld. Use Getsymboladdress instead.

2015-03-05

Some traps of LLVM Mcjit