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Re: [PATCH, MPX, 2/X] Pointers Checker [18/25] CCP (Stack store/restore)


2013/11/21 Jeff Law <law@redhat.com>:
> On 11/18/13 03:54, Ilya Enkovich wrote:
>>
>> Hi,
>>
>> Here is a patch to support BUILT_IN_CHKP_BNDRET and
>> BUILT_IN_CHKP_BIND_BOUNDS in BUILT_IN_STACK_SAVE result uses.
>>
>> Thanks,
>> Ilya
>> --
>> 2013-11-15  Ilya Enkovich  <ilya.enkovich@intel.com>
>>
>>         * tree-ssa-ccp.c (insert_clobber_before_stack_restore): Handle
>>         BUILT_IN_CHKP_BNDRET and BUILT_IN_CHKP_BIND_BOUNDS calls.
>
> I've looked at this a few times, but I'm having trouble seeing why you need
> this code.  Can you please explain why you're doing this?
>
> Sample code & dumps are helpful, as always:-)

The code in insert_clobber_before_stack_restore is trying to find
BUILT_IN_STACK_RESTORE call matching given BUILT_IN_STACK_SAVE call.
It does search by analyzing uses of BUILT_IN_STACK_SAVE lhs. It does
not expect any uses except BUILT_IN_STACK_RESTORE call, PHI nodes, SSA
name copy and debug statements.

In instrumented code additional possible users are
BUILT_IN_CHKP_BNDRET and BUILT_IN_CHKP_BIND_BOUNDS calls. The first
one gets bounds returned by BUILT_IN_STACK_RESTORE.  The second one
binds these bound with pointer to pass to BUILT_IN_STACK_SAVE. Also to
find BUILT_IN_STACK_SAVE we need to search in uses of
BUILT_IN_CHKP_BIND_BOUNDS result.

Thanks,
Ilya

>
> jeff
>


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