Parallella Community

mikebell,

I tend to agree with all three of your suggestions! If you want to go ahead and submit compiler issue request (one each) that would help out a lot!

https://github.com/adapteva/epiphany-sdk/issues

(if you don't have time, then I will grab the text out of this post and submit issues...)

Andreas

I've raised issues for 2 and 3 (and given a proposed patch that works-for-me™ for issue 2).

It turns out raising that number of registers is harder than I expected, and is really a core gcc issue, not an epiphany specific one. So I haven't raised an issue for that right now.

Mike

On further investigation I found it didn't seem too hard to get up to 60 registers in use in an asm block (which is really only a bit more than 30 because of the double counting for read/write regs).

I've raised an issue with a link to a commit that appears to work for me. Again, more testing by someone with more experience would be nice!

Mike

Reduce the amount of instructions used for stack manipulation!

Upon analysis of disassembled object code I found that between 10% and 20% of instructions are just managing the stack when calling/leaving a function. There are multiple ways to do this, from changing register use rules to having dedicated functions to manage the stack.

I'm not sure how to command GCC to do this but if you could mark functions or specific variables to use low index registers so that the 16-bit instructions could be used instead of 32-bit ones, that could save a lot of space.

better yet, having a gcc flag to aggressively try and save space by using 16-bit instructions as much as possible would be good.