Re: [Tinycc-devel] Jump optimization questions - commit: 8227db3a

[Ekaitz Zarraga]

Hi,

Sorry for insisting but I kept working on this and found no solution.

vtop->r and vtop->cmp_r are used interchangeably in some parts of the codebase 
and I don't really understand why. I tried using vtop->r but it just generates 
invalid values.

Also RISC-V does not use flags so the process is different than in the other 
architectures so I don't have a good reference to look at in any others.

Does anyone have an idea about how can I tackle this?

I managed to make the code generate the correct branch instructions but I can't 
figure out how to obtain the correct registers.

Thanks a lot,
Ekaitz


------- Original Message -------
On Thursday, August 11th, 2022 at 1:36 PM, Ekaitz Zarraga <ekaitz@elenq.tech> 
wrote:


> Hi,
> 
> I think I have it mostly working following your advice but I cannot find how 
> to map v->cmp_r to the field that was storing that information before the 
> commit.
> 
> 
> In the gjmp_cond in riscv:
> 
> ``` c
> ST_FUNC int gjmp_cond(int op, int t)
> {
> int tmp;
> int a = vtop->cmp_r & 0xff;
> 
> int b = (vtop->cmp_r >> 8) & 0xff;
> 
> switch (op) {
> ```
> 
> What do I need to replace `a` and `b` with to use the previous register 
> access but I can't find how to do that.
> 
> Could you please help me?
> 
> Thank you,
> Ekaitz
> 
> 
> ------- Original Message -------
> On Wednesday, August 10th, 2022 at 1:53 PM, Ekaitz Zarraga ekaitz@elenq.tech 
> wrote:
> 
> 
> 
> > Hi,
> > 
> > On Wednesday, August 10th, 2022 at 1:43 PM, grischka grishka@gmx.de wrote:
> > 
> > > On 09.08.2022 20:39, Ekaitz Zarraga wrote:
> > > 
> > > > Hi all,
> > > > 
> > > > I'm working on the RISC-V bootstrapping efforts for Guix, and I have to 
> > > > backport the RISC-V backend to an older TinyCC version we have patched 
> > > > in order to be able to build it with a simpler compiler.
> > > 
> > > I wonder why not just apply these patches to the newer tcc then?
> > 
> > Mostly because the compiler we use to compile TinyCC does not provide all 
> > the C constructs modern TinyCC is using nowadays, so we can't use it now.
> > We may be able to do it in the future, but our current compiler chain does 
> > not allow us to do that.
> > 
> > > > The process worked mostly ok, but I can't understand very well the 
> > > > `gtst` function in the generation part, and I need to write it from 
> > > > scratch as the commit 8227db3a changed how the tests and jumps are 
> > > > managed.
> > > 
> > > Actually that commit was to put the former gtst() function in its pieces,
> > > now gjmp_cond(t, op) to handle VT_CMP, and gjmp_append(n, t) for the
> > > former VT_JMP "optimization" part.
> > 
> > Do you mean the commit was done to split the function in two?
> > I'll take a deeper look and see if I can undo it properly.
> > 
> > Thanks for the help
> > 
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