On 12/11/15 13:26, Richard Biener wrote:
On Thu, Nov 12, 2015 at 12:37 PM, Tom de Vries <tom_devr...@mentor.com> wrote:
Hi,
[ See also related discussion at
https://gcc.gnu.org/ml/gcc-patches/2012-07/msg00452.html ]
this patch removes the usage of first_pass_instance from pass_vrp.
the patch:
- limits itself to pass_vrp, but my intention is to remove all
usage of first_pass_instance
- lacks an update to gdbhooks.py
Modifying the pass behaviour depending on the instance number, as
first_pass_instance does, break compositionality of the pass list. In other
words, adding a pass instance in a pass list may change the behaviour of
another instance of that pass in the pass list. Which obviously makes it
harder to understand and change the pass list. [ I've filed this issue as
PR68247 - Remove pass_first_instance ]
The solution is to make the difference in behaviour explicit in the pass
list, and no longer change behaviour depending on instance number.
One obvious possible fix is to create a duplicate pass with a different
name, say 'pass_vrp_warn_array_bounds':
...
NEXT_PASS (pass_vrp_warn_array_bounds);
...
NEXT_PASS (pass_vrp);
...
But, AFAIU that requires us to choose a different dump-file name for each
pass. And choosing vrp1 and vrp2 as new dump-file names still means that
-fdump-tree-vrp no longer works (which was mentioned as drawback here:
https://gcc.gnu.org/ml/gcc-patches/2012-07/msg00453.html ).
This patch instead makes pass creation parameterizable. So in the pass list,
we use:
...
NEXT_PASS_WITH_ARG (pass_vrp, true /* warn_array_bounds_p */);
...
NEXT_PASS_WITH_ARG (pass_vrp, false /* warn_array_bounds_p */);
...
This approach gives us clarity in the pass list, similar to using a
duplicate pass 'pass_vrp_warn_array_bounds'.
But it also means -fdump-tree-vrp still works as before.
Good idea? Other comments?
It's good to get rid of the first_pass_instance hack.
I can't comment on the AWK, leaving that to others. Syntax-wise I'd hoped
we can just use NEXT_PASS with the extra argument being optional...
I suppose I could use NEXT_PASS in the pass list, and expand into
NEXT_PASS_WITH_ARG in pass-instances.def.
An alternative would be to change the NEXT_PASS macro definitions into
vararg variants. But the last time I submitted something with a vararg
macro ( https://gcc.gnu.org/ml/gcc-patches/2015-09/msg00794.html ), I
got a question about it (
https://gcc.gnu.org/ml/gcc-patches/2015-09/msg00912.html ), so I tend to
avoid using vararg macros.
I don't see the need for giving clone_with_args a new name, just use an overload
of clone ()?
That's what I tried initially, but I ran into:
...
src/gcc/tree-pass.h:85:21: warning: ‘virtual opt_pass*
opt_pass::clone()’ was hidden [-Woverloaded-virtual]
virtual opt_pass *clone ();
^
src/gcc/tree-vrp.c:10393:14: warning: by ‘virtual opt_pass*
{anonymous}::pass_vrp::clone(bool)’ [-Woverloaded-virtual]
opt_pass * clone (bool warn_array_bounds_p) { return new pass_vrp
(m_ctxt, warn_array_bounds_p); }
...
Googling the error message gives this discussion: (
http://stackoverflow.com/questions/16505092/confused-about-virtual-overloaded-functions
), and indeed adding
"using gimple_opt_pass::clone;"
in class pass_vrp makes the warning disappear.
I'll submit an updated version.
Thanks,
- Tom
> [ideally C++ would allow us to say that only one overload may be
> implemented]
