(R5900) Implementing Vector Support

[Richard Henderson]

On 05/29/2016 12:59 AM, Woon yung Liu wrote:
> Hi Richard,
>
> I have solved the problems with the mulv8hi3 pattern; I needed to adjust the code within mips.c to allow the double-sized vector modes and to allow vector modes into the LO+HI accumulators.

Yes, I should have mentioned that you would need to do that.

> What is the correct way to change the mode of registers? For example, I am doing this to change the mode for a register to V4SI within an expand:
>            reg = gen_rtx_REG(V4SImode, REGNO (reg));

This is almost always incorrect, and certainly before reload.
You need to use gen_lowpart.  There are examples in the code
fragments that I sent the other week.

> Finally, what is the difference between define_expand and define_insn_and_split? When should I ever use define_insn_and_split?

You need to read the gcc internals documentation.  They are all three different 
uses, though there is some overlap between define_insn and define_expand.

> Are define_insn_and_split patterns used to avoid pseudo registers?

No.


r~