[LLVMdev] Why the same code is much slower in JIT compared to separate executable?

[Török Edwin]

On 04/29/2010 12:13 PM, Yuri wrote:
> Török Edwin wrote:
>> How long does it take for llc to compile it?
>> Remember that the JIT includes code generation time
> 
> llc takes almost no time (0.00 user as measured by time), code is tiny.
> 

Are you using 2.6 or 2.7, 32-bit or 64-bit?

With 2.7 on x86-64 I get:

lli:
real    0m9.564s
user    0m9.557s
sys     0m0.004s

a.out:
real    0m12.105s
user    0m12.029s
sys     0m0.008s

So JIT is actually faster here.

With a 32-bit build, I get this with a.out:
real    0m15.052s
user    0m14.977s
sys     0m0.004s

And this with the JIT (Release-Asserts):
real    0m17.963s
user    0m17.581s
sys     0m0.004s

Best regards,
--Edwin