[ft-devel] Accelerate TrueType interpreter with JIT compiling?

[Zoltán Herczeg]

Hi,

I am Zoltan Herczeg, the developer of the sljit JIT compiler. I am new to 
FreeType, but if I understand correctly TrueType hinting is done by a byte-code 
interpreter (ttinterp). My question is, is it worth to accelerate this process 
by JIT? I mostly saw simple uint32 computations in the code, which can be 
translated to sljit instructions (LIR) easily. However, JIT compiling has a 
considerable overhead, so it is only worth for frequently used code paths (for 
example sljit is used for accelerating regular expressions and network packet 
filtering). May I ask the purpose of this interpreter? Is it only used for font 
loading, or has other purposes? Is the same program runs for all glyphs for the 
same font (or multiple fonts)? What is the typical program length (number of 
bytecode instructions)? Do you have any measurements about the ratio of 
interpreted runtime compared to the total time consumed by freetype?

Regards,
Zoltan