On Mon, Oct 16, 2017 at 10:25:37 -0700, Richard Henderson wrote: > Since we cast indicies to pointers, reserving 0 allows
s/indicies/indices/ > us to use NULL for unused/dummy instead of (T *)-1. > > Signed-off-by: Richard Henderson <richard.hender...@linaro.org> > --- (snip) > @@ -737,7 +737,7 @@ extern bool parallel_cpus; > static inline size_t temp_idx(TCGTemp *ts) > { > ptrdiff_t n = ts - tcg_ctx.temps; > - tcg_debug_assert(n >= 0 && n < tcg_ctx.nb_temps); > + tcg_debug_assert(n > 0 && n < tcg_ctx.nb_temps); > return n; > } > > diff --git a/tcg/tcg.c b/tcg/tcg.c > index 129aecca60..7cf39f7067 100644 > --- a/tcg/tcg.c > +++ b/tcg/tcg.c > @@ -333,7 +333,10 @@ void tcg_context_init(TCGContext *s) > int *sorted_args; > > memset(s, 0, sizeof(*s)); > - s->nb_globals = 0; > + /* Reserve temp index 0 so that, with the funny casting that we do, > + the first one doesn't look like NULL. */ > + s->nb_globals = 1; > + s->nb_temps = 1; > > /* Count total number of arguments and allocate the corresponding > space */ I like this change, although operating on the 0th element makes me uneasy. For instance, I managed to trigger the above assert by manually calling dump_regs (it is otherwise called before aborting, which is why you missed it.) This fixes it: diff --git a/tcg/tcg.c b/tcg/tcg.c index 7cf39f7..49176e0 100644 --- a/tcg/tcg.c +++ b/tcg/tcg.c @@ -2034,7 +2034,7 @@ static void dump_regs(TCGContext *s) int i; char buf[64]; - for(i = 0; i < s->nb_temps; i++) { + for (i = 1; i < s->nb_temps; i++) { ts = &s->temps[i]; printf(" %10s: ", tcg_get_arg_str_ptr(s, buf, sizeof(buf), ts)); switch(ts->val_type) { Is it worth changing other [0, nb_temps/globals) loops to start from 1? Thanks, E.