finalizeObject function implemetation in MCJIT is wrong

Hi all.

I found some issue in implementation of finalizeObject function in MCJIT.cpp. If you look at the source code of the function, you can notice that machine code for second “owned” module will never be generated if it doesn’t depend on the first one. More over it will cause a crash if entry point isn’t in first module. Implementation of finalizeObject using for loop will omit every other module in OwnedModules, because function generateCodeForModule moves module form “added” to “loaded”.
Am I right?



[+Lang, owner of JITs, defender of register allocators, etc]

Hi Radek,

Sorry for the delayed response. I haven’t had time to check your analysis yet, but you’re probably right: MCJIT’s support for multiple modules in a single instance is patchy at best.

Do you have a test case (e.g. an lli invocation) that triggers this bug, or is this something you discovered just by reading the code?


I will prepare this test case with lli ASAP.

Hi Lang.

I prepared the test case.
Download file from attachment.
Compile main.cpp and run it. test1.ll and test2.ll should be in the working folder.
When you uncomment line 49 in main.cpp it starts working fine.

My configuration is:
llvm 3.5
msvc 11 (VS 2012)
architecture x86


P.S. After preparing this test case I noticed that this bug is fixed in the newest implementation of MCJIT in llvm trunk branch. :slight_smile:

test2.ll (74 Bytes)

test1.ll (79 Bytes)

main.cpp (1.49 KB)

Ahh. Glad to hear that things have improved on trunk. :slight_smile:

  • Lang.