Re: [patch] fix regrename pass to ensure renamings produce valid insns

[Kito Cheng <kito.cheng@gmail.com>]

Hi all:

This patch seem will broken when disable assert checking for c6x....

Index: gcc/config/c6x/c6x.c
===================================================================
--- gcc/config/c6x/c6x.c (revision 225104)
+++ gcc/config/c6x/c6x.c (working copy)
@@ -3516,7 +3516,7 @@ try_rename_operands (rtx_insn *head, rtx
   best_reg =
     find_rename_reg (this_head, super_class, &unavailable, old_reg, true);

-  regrename_do_replace (this_head, best_reg);
+  gcc_assert (regrename_do_replace (this_head, best_reg));

   count_unit_reqs (new_reqs, head, PREV_INSN (tail));
   merge_unit_reqs (new_reqs);
@@ -3529,7 +3529,7 @@ try_rename_operands (rtx_insn *head, rtx
        unit_req_imbalance (reqs), unit_req_imbalance (new_reqs));
     }
   if (unit_req_imbalance (new_reqs) > unit_req_imbalance (reqs))
-    regrename_do_replace (this_head, old_reg);
+    gcc_assert (regrename_do_replace (this_head, old_reg));
   else
     memcpy (reqs, new_reqs, sizeof (unit_req_table));


On Mon, Jun 29, 2015 at 5:08 AM, Sandra Loosemore
<sandra@codesourcery.com> wrote:
> On 06/24/2015 09:46 PM, Jeff Law wrote:
>>
>> On 06/23/2015 07:00 PM, Sandra Loosemore wrote:
>>>
>>> On 06/18/2015 11:32 AM, Eric Botcazou wrote:
>>>>>
>>>>> The attached patch teaches regrename to validate insns affected by each
>>>>> register renaming before making the change.  I can see at least two
>>>>> other ways to handle this -- earlier, by rejecting renamings that
>>>>> result
>>>>> in invalid instructions when it's searching for the best renaming; or
>>>>> later, by validating the entire set of renamings as a group instead of
>>>>> incrementally for each one -- but doing it all in regname_do_replace
>>>>> seems least disruptive and risky in terms of the existing code.
>>>>
>>>>
>>>> OK, but the patch looks incomplete, rename_chains should be adjusted
>>>> as well,
>>>> i.e. regrename_do_replace should now return a boolean.
>>>
>>>
>>> Like this?  I tested this on nios2 and x86_64-linux-gnu, as before, plus
>>> built for aarch64-linux-gnu and ran the gcc testsuite.
>>>
>>> The c6x back end also calls regrename_do_replace.  I am not set up to
>>> build or test on that target, and Bernd told me off-list that it would
>>> never fail on that target anyway so I have left that code alone.
>>>
>>> -Sandra
>>>
>>> regrename-2.log
>>>
>>>
>>> 2015-06-23  Chung-Lin Tang<cltang@codesourcery.com>
>>>         Sandra Loosemore<sandra@codesourcery.com>
>>>
>>>     gcc/
>>>     * regrename.h (regrename_do_replace): Change to return bool.
>>>     * regrename.c (rename_chains): Check return value of
>>>     regname_do_replace.
>>>     (regrename_do_replace): Re-validate the modified insns and
>>>     return bool status.
>>>     * config/aarch64/cortex-a57-fma-steering.c (rename_single_chain):
>>>     Update to match rename_chains changes.
>>
>> As Eric mentioned, please put an assert to verify that the call from the
>> c6x backend never fails.
>>
>> The regrename and ARM bits are fine.
>>
>> Do you have a testcase that you can add to the suite?  If so it'd be
>> appreciated if you could include that too.
>>
>> Approved with the c6x assert if a testcase isn't available or
>> exceedingly difficult to produce.
>
>
> Thanks.  I've committed the attached version.
>
> Re the testcase, this fixed 16 FAILs on existing tests in the gcc testsuite
> with the forthcoming nios2 load/store multiple instruction support, all
> assembler errors due to the bad instructions being generated.  There's
> nothing I can do on nios2 for a testcase until I get those patches committed
> (I'm still trying to re-test and tidy them up for submission), plus I think
> the failures are rather fragile -- depending on the register allocator
> choosing an initial register numbering that allows peephole optimizers to
> trigger, etc.  But, I will revisit this later and see what I can do.
>
> -Sandra
>