On Wed, 2012-08-01 at 22:59 +0200, Stefan Israelsson Tampe wrote: > Hi, > > The byte-code -> native-code compiler is does serve my needs pretty well > now. It should really > soon be possible to add code that will auto compile bytecode versions to > native versions. The compiler is not perfect and some instructions is > missing. But it can go from VM->NATIVE->VM and so on so whenever there is > missing instruction the compiler can bail out to vm code. What's left is > to be able to go from VM to Native returning multiple values and in all > call positions. > > To note > > * the code is for x86-64, linux. > > * Windows have another calling convention => the assembler has to be recoded > => we need compilers for all interesting combinations of operating > systems and native targets > > * Using the C-stack is nice because the native push and pop instructions > can be used as well as > brk-ings makes for automatic stack growth? also calling out c functions > can be fast. On the > other hand stack traces is defunct with this code and I'm uncertain how > the prompting will > cope with this feature. It's probably better to use a separate stack for > the native code and model > it like the wip-rtl stack. On the other hand it has been convenient to > use it as a stack to save > variables before calling out to helper c-functions, but these helper > functions usually is on the slow > path and the savings can be done using helper registers that is local to > the vm a little bit slower > but doable. Not sure what path to take here. > > * Writing assembler is really tough. Because debugging is really difficult. >
IMO, we don't have to write assembler again, since GNU Binutils does. The only necessary work is to map bytecode->asm, and add a AOT option with a script into 'guild' for calling Binutils. We may borrow some work from GCC. I don't know if it's easy, but GCC uses Lisp-like thing to handle machine-description. Though it could be interesting, it's a lot of work todo. Then it could support many platforms rather than x86. > * To ease things I compiled C code and examined the assembler => fragile > and difficult to port the > code. The final version needs to put more effort into probing for > constants used in the generated > assembler. > > * x86 code is pretty different because of the low number of registers and > invariant registers over c-call's > > * prompt and aborts are tricky instructions! > > Example: > as an example reducing a list of 1000 elements with a function that is > basically + a 4x increase in performance when compiling to native code > could be seen. This are typical figures for what one can expect to improve > in speed. A smarter usage of registers and less poping and pushing (RTL) > could mean that we can increase the speedup from stable-2.0 even further. > > > I will next week start working on the RTL branch porting the current setup > but use the rtl stack in stead of the native C stack. > > Regards > /Stefan
