Re: [PATCH 1/2] tcg: Do not kill globals at conditional branches

[Alex Bennée]

Richard Henderson <richard.henderson@linaro.org> writes:

> We can easily register allocate the entire extended basic block
> (in this case, the set of blocks connected by fallthru), simply
> by not discarding the register state at the branch.
>
> This does not help blocks starting with a label, as they are
> reached via a taken branch, and that would require saving the
> complete register state at the branch.
>
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
>  include/tcg/tcg-opc.h |  7 +++---
>  include/tcg/tcg.h     |  4 +++-
>  tcg/tcg.c             | 55 +++++++++++++++++++++++++++++++++++++++++--
>  3 files changed, 60 insertions(+), 6 deletions(-)
>
<snip>
>  
> +/*
> + * liveness analysis: conditional branch: all temps are dead,
> + * globals and local temps should be synced.
> + */
> +static void la_bb_sync(TCGContext *s, int ng, int nt)
> +{
> +    la_global_sync(s, ng);
> +
> +    for (int i = ng; i < nt; ++i) {
> +        if (s->temps[i].temp_local) {
> +            int state = s->temps[i].state;
> +            s->temps[i].state = state | TS_MEM;
> +            if (state != TS_DEAD) {
> +                continue;

It took me a few scans of this function before I realised the continue
was to avoid the la_reset_pref at the end. Not sure if it can be made
any neater though:

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>

-- 
Alex Bennée