Re: [patch 14/24] Immediate Values - x86 Optimization

H. Peter Anvin
2007-12-21T03:38:51Z

Mathieu Desnoyers wrote:
>
> Argh.. Rusty asked to have a simplified version first, and then to
> implement the "more complex" one on top of it. However, in order to get
> the reentrancy I need for the markers, I need the complex version of the
> immediate values. Therefore, you find, in this patchset, the simple
> version first, and then, the more complex one implemented on top.
>
> About this patch header, the initial idea was to use the "Q" and "R"
> constraints, but, as stated just below, the "q" and "r" constraints are
> used instead to make sure the REX prefixed opcodes for 1, 2, and 4 bytes
> immediate values are never used. So the complete header follows the
> source code, it's just that this paragraph could be clearer.
>

Then you have it backwards. "Q" and "R" avoid REX prefixes, "q" and "r"
DO NOT.

-hpa