[LLVMdev] JIT compilation 2-3 times slower in latest LLVM snapshot (original) (raw)

Dibyendu Majumdar mobile at majumdar.org.uk
Sat Jul 11 05:09:28 PDT 2015

On 11 July 2015 at 12:45, Dibyendu Majumdar <mobile at majumdar.org.uk> wrote:

I updated my clone of the LLVM github mirror today and I am finding that the JIT compilation is now 2-3 times slower. The last time I refreshed was maybe 2 weeks ago. Is there a known change that would explain this?

This is on Windows 8.1 64-bit. I am using MCJIT.

To give you some idea:

On Linux VM running on the same machine, using LLVM 3.6.1, the time taken for my test:

../build/lua -e"_U=true;ravi.optlevel(2); ravi.auto(true,1)" all.lua total time: 70.80s (wall time: 73s)

On Windows natively running against latest LLVM snapshot:

..\build\Release\lua.exe -e"_U=true; ravi.optlevel(2); ravi.auto(true,1)" all.lua total time: 333.65s (wall time: 333s)

My benchmarks run fine hence my view that it is taking longer to JIT rather than an issue with the generated code.

Unfortunately I don't have the timing I was getting previously but from memory it was roughly similar to the Linux timing above.

Thanks and Regards Dibyendu

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