[Libre-soc-isa] [Bug 1056] questions and feedback (v2) on OPF RFC ls010

bugzilla-daemon at libre-soc.org bugzilla-daemon at libre-soc.org
Thu Jun 1 02:20:39 BST 2023


https://bugs.libre-soc.org/show_bug.cgi?id=1056

--- Comment #45 from Paul Mackerras <paulus at ozlabs.org> ---
On further reflection, it seems like the point being made above by Luke might
be something along these lines:

If you have a vector of elements stored in a register, and you want to operate
on the 0th element and you don't care about corrupting the others, then you can
in many cases use a scalar instruction instead of the equivalent vector
instruction with VL=1. This is a valuable property.

This would be true for things like add, subtract, multiply, left shift, and
bitwise operations, but not divide, right shift, compare.

I can see that this is a useful property.

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