On 16/06/20 11:42 +0100, Richard Sandiford wrote:
Jonathan Wakely <jwak...@redhat.com> writes:
+ template<typename ...Ts>
+ rtx_insn *operator() (Ts... args...) const
Why is this declared as a variadic template **and** a varargs function?
I think the second ellipsis is wrong, it should be just:
+ template<typename ...Ts>
+ rtx_insn *operator() (Ts... args) const
Oops, yes.
And this seems like a more direct way to say "a list of N rtx types"
where N is sizeof...(args):
diff --git a/gcc/recog.h b/gcc/recog.h
index 0a71a02c4a9..fd22c58c92a 100644
--- a/gcc/recog.h
+++ b/gcc/recog.h
@@ -294,10 +294,13 @@ struct insn_gen_fn
{
typedef void (*stored_funcptr) (void);
+ template<typename T> using rtx_t = rtx;
+
template<typename ...Ts>
- rtx_insn *operator() (Ts... args...) const
+ rtx_insn *operator() (Ts... args) const
{
- return ((rtx_insn *(*) (decltype(args, NULL_RTX)...)) func) (args...);
+ using funcptr = rtx_insn * (*) (rtx_t<Ts>...);
+ return ((funcptr) func) (args...);
}
// This is for compatibility of code that invokes functions like
The rtx_t<T> alias is the type 'rtx' for any T. The pack expansion
rtx_t<Ts>... is a list of rtx the same length as the pack Ts.
Yeah. As mentioned on IRC, I'd originally done it like this, but didn't
like the ad-hoc type alias. I can't remember what name I'd used, but the
problem in both cases is/was that the ad-hoc name looks odd when you're
used to seeing plain “rtx”. It also felt weird to expose this kind of
internal, function-specific implementation detail at insn_gen_fn scope.
Using decltype also gave nicer error messages, e.g.:
invalid conversion from ‘int’ to ‘rtx {aka rtx_def*}’
instead of:
invalid conversion from ‘int’ to ‘insn_gen_fn::rtx_t<int> {aka rtx_def*}’
I think the latter is likely to confuse people when they see it
for the first time.
So in some ways I'd prefer to keep the decltype and just add a void cast
to suppress the warning. (Seems odd to warn about expressions having no
effect in an unevaluated context.)
Yes, arguably a G++ bug.
But how about the below instead? Hopefully the alias name is mnemonic
enough.
Works for me, thanks.
