[J-core] Fwd: ISA manual for SH-2

[D. Jeff Dionne]

On May 26, 2017, at 20:50, BGB <cr88192 at gmail.com> wrote:
> 
> ...not used by GCC in my tests

It is better to look at the gcc code generator first, to determine what it might emit and what might trigger it to do so, before one assumes anything about what parts of the ISA is does or doesn't use from (I assume) black box compilation tests.   There have been cases over the years where I had assumed gcc would not emit something, only to find that while it is hard to trigger a specific instruction pattern...  it does in fact happen.  Those cases were often related to trying to do odd things with e.g. position independent code.

Those vector ops and MAC instructions were the ones I was thinking about a few mails ago, in the context of signal processing.  C is often not great at inferring things (to use a term I usually associate with hardware synthesis) like these vector ops, especially for a code generator like sh4 where the user and developer base is limited.   We really need to get someone to maintain that stuff.   Hitachi/Renesas has Code Sorcery doing some of that, there may be work that wasn't merged somewhere, along the lines of the GDB patches that people have been trying to get upstream.

Now, BGB, if we could just find a way to integrate your efforts into the J-Core project so that the work advances the project's cause, instead of going off on a completely different path ;^}

J.