Re: [PING] Re: [PATCH] Fix PR50183

[Richard Guenther <richard dot guenther at gmail dot com>]

On Thu, Sep 29, 2011 at 12:10 AM, William J. Schmidt
<wschmidt@linux.vnet.ibm.com> wrote:
> Hi there,
>
> Ping. ?I'm seeking approval for this fix on trunk and 4_6-branch.
> Thanks!

Ok.

Thanks,
Richard.

> Bill
>
> On Tue, 2011-09-13 at 17:55 -0500, William J. Schmidt wrote:
>> Greetings,
>>
>> The code to build scops (static control parts) for graphite first
>> rewrites loops into canonical loop-closed SSA form. ?PR50183 identifies
>> a scenario where the results do not fulfill all required invariants of
>> this form. ?In particular, a value defined inside a loop and used
>> outside that loop must reach exactly one definition, which must be a
>> single-argument PHI node called a close-phi. ?When nested loops exist,
>> it is possible that, following the rewrite, a definition may reach two
>> close-phis. ?This patch corrects that problem.
>>
>> The problem arises because loops are processed from outside in. ?While
>> processing a loop, duplicate close-phis are eliminated. ?However,
>> eliminating duplicate close-phis for an inner loop can sometimes create
>> duplicate close-phis for an already-processed outer loop. ?This patch
>> detects when this may have occurred and repeats the removal of duplicate
>> close-phis as necessary.
>>
>> The problem was noted on ibm/4_6-branch and 4_6-branch; it is apparently
>> latent on trunk. ?The same patch can be applied to all three branches.
>>
>> Bootstrapped and regression-tested on powerpc64-linux. ?OK to commit to
>> these three branches?
>>
>> Thanks,
>> Bill
>>
>>
>> 2011-09-13 ?Bill Schmidt ?<wschmidt@linux.vnet.ibm.com>
>>
>> ? ? ? * graphite-scop-detection.c (make_close_phi_nodes_unique): ?New
>> ? ? ? forward declaration.
>> ? ? ? (remove_duplicate_close_phi): Detect and repair creation of
>> ? ? ? duplicate close-phis for a containing loop.
>>
>>
>> Index: gcc/graphite-scop-detection.c
>> ===================================================================
>> --- gcc/graphite-scop-detection.c ? ? (revision 178829)
>> +++ gcc/graphite-scop-detection.c ? ? (working copy)
>> @@ -30,6 +30,9 @@ along with GCC; see the file COPYING3. ?If not see
>> ?#include "tree-pass.h"
>> ?#include "sese.h"
>>
>> +/* Forward declarations. ?*/
>> +static void make_close_phi_nodes_unique (basic_block);
>> +
>> ?#ifdef HAVE_cloog
>> ?#include "ppl_c.h"
>> ?#include "graphite-ppl.h"
>> @@ -1231,6 +1234,13 @@ remove_duplicate_close_phi (gimple phi, gimple_stm
>> ? ? ? SET_USE (use_p, res);
>>
>> ? ? ? ?update_stmt (use_stmt);
>> +
>> + ? ? ?/* It is possible that we just created a duplicate close-phi
>> + ? ? ?for an already-processed containing loop. ?Check for this
>> + ? ? ?case and clean it up. ?*/
>> + ? ? ?if (gimple_code (use_stmt) == GIMPLE_PHI
>> + ? ? ? && gimple_phi_num_args (use_stmt) == 1)
>> + ? ? make_close_phi_nodes_unique (gimple_bb (use_stmt));
>> ? ? ?}
>>
>> ? ?remove_phi_node (gsi, true);
>>
>>
>
>
>