On 08/03/2015 05:42 AM, Kai Tietz wrote:
2015-08-03 5:49 GMT+02:00 Jason Merrill <ja...@redhat.com>:
On 07/31/2015 05:54 PM, Kai Tietz wrote:
The "STRIP_NOPS-requirement in 'reduced_constant_expression_p'" I could
remove, but for one case in constexpr. Without folding we don't do
type-sinking/raising.
Right.
So binary/unary operations might be containing cast, which were in the
past unexpected.
Why aren't the casts folded away?
On such cast constructs, as for this vector-sample, we can't fold away
Which testcase is this?
the cast chain. The difference here to none-delayed-folding branch is
that the cast isn't moved out of the plus-expr. What we see now is
(plus ((vec) (const vector ...) { .... }), ...). Before we had (vec)
(plus (const vector ...) { ... }).
How could a PLUS_EXPR be considered a reduced constant, regardless of
where the cast is?
On verify_constant we check by reduced_constant_expression_p, if value is
a constant. We don't handle here, that NOP_EXPRs are something we want to
look through here, as it doesn't change anything if this is a constant, or
not.
NOPs around constants should have been folded away by the time we get there.
Not in this cases, as the we actually have here a switch from const to
none-const. So there is an attribute-change, which we can't ignore in
general.
I wasn't suggesting we ignore it, we should be able to change the type
of the vector_cst.
But I agree that for constexpr's we could special case cast
from const to none-const (as required in expressions like const vec v
= v + 1).
Right. But really this should happen in convert.c, it shouldn't be
specific to C++.
Jason
