Re: [PATCH] target/arm: Fix SMLAD incorrect setting of Q bit

[Peter Maydell]

On Fri, 9 Oct 2020 at 23:36, Richard Henderson
<richard.henderson@linaro.org> wrote:
>
> On 10/9/20 1:48 PM, Peter Maydell wrote:
> > On Fri, 9 Oct 2020 at 15:47, Peter Maydell <peter.maydell@linaro.org> wrote:
> >> +        tcg_gen_extr_i64_i32(t1, t2, p64);
> >
> > Oh, I forgot to mention, but it looks like extr_i64_i32
> > isn't documented in tcg/README. Is that because it isn't
> > really a TCG IR op, or just an omission?
>
> Because it's not an IR op.  It's the combo of extrl and extrh.

We really should figure out somewhere to document the
interface and operations that frontends can use. (Among
other important things, extr_i64_i32 is usable generically,
but extrl/extrh are 64-bit hosts only according to tcg/README,
so if you trusted the README docs then you'd end up
trying to synthesize this out of shifts and trunc.)

thanks
-- PMM