Optimizations

Support for multiple optimizations is available since release 0.7. These optimizations may speed up your code but the code generation may take longer. Therefore, you can turn particular optimization off and on using jit_disable_optimization and jit_enable_optimization functions, respectively. Currently, there are available the following optimizations:

• JIT_OPT_OMIT_UNUSED_ASSIGNEMENTS -- compiler skips unused assignments. (Turned off by default.)
• JIT_OPT_JOIN_ADDMUL -- if possible, compiler joins adjacent mul and add (or two add's) into one LEA operation (Turned on by default.)
• JIT_OPT_OMIT_FRAME_PTR -- if possible, compiler skips prolog and epilogue of the function. This significantly speeds up small functions. (Turned on by default.)

The optimized code for above mentioned example looks like this:

00000000 <main>:
   0:   8b 4c 24 04             mov    ecx,DWORD PTR [esp+0x4]
   4:   8d 41 01                lea    eax,[ecx+0x1]
   7:   c3                      ret

Or, like this:

0000000000000000 <main>:
   0:   48 8d 47 01             lea    rax,[rdi+1]
   4:   c3                      ret

© Petr Krajča, 2015