Hi,
On Mon, 27 Jul 2015, Richard Biener wrote:
> > > static inline tree
> > > gimple_assign_rhs1 (const_gimple gs)
> > > {
> > > GIMPLE_CHECK (gs, GIMPLE_ASSIGN);
> > > return gimple_op (gs, 1);
> > > }
> > >
> > > and the hidden checking is due to gimple_op being
> > >
> > > static inline tree *
> > > gimple_ops (gimple gs)
> > > {
> > > size_t off;
> > >
> > > /* All the tuples have their operand vector at the very bottom
> > > of the structure. Note that those structures that do not
> > > have an operand vector have a zero offset. */
> > > off = gimple_ops_offset_[gimple_statement_structure (gs)];
> > > gcc_gimple_checking_assert (off != 0);
I once experimented with making the multiple checking and removing the
actual memory accesses by exposing the real content of gss_for_code_[]
(for gss_for_code(), used by gimple_statement_structure()) and
gimple_ops_offset_[] to the inlined functions, i.e. by defining them in
gimple.h, not just declaring them.
Still wouldn't help the -O0 case, but with -O2 only the first check for
being GIMPLE_ASSING remains, everything else is constant folded.
> > > The simplest thing would be to use
> > >
> > > GIMPLE_CHECK (gs, GIMPLE_ASSIGN);
> > > return as_a <const gassign *> (gs)->op[1];
> > >
> > > but that's not optimal either because we check we have a gassign
> > > again (not optimized in stage1). So I decided to invent a fancy
> > > as_a which reports errors similar to GIMPLE_CHECK and makes the
> > > code look like
I'm confused. as_a<> already does checking:
as_a (U *p)
{
gcc_checking_assert (is_a <T> (p));
return is_a_helper <T>::cast (p);
}
(were the is_a<> variant here has the same test as GIMPLE_CHECK).
So, if you have the as_a call, you can as well simply remove the
GIMPLE_CHECK, and be done with it, without ...
> > > const gassign *ass = GIMPLE_CHECK2<const gassign *> (gs);
... introducing this. What am I missing?
Ciao,
Michael.
