On Fri, Mar 30, 2012 at 5:43 PM, Bin.Cheng <[email protected]> wrote:
> On Fri, Mar 30, 2012 at 4:15 PM, Richard Guenther
> <[email protected]> wrote:
>> On Thu, Mar 29, 2012 at 5:25 PM, Bin.Cheng <[email protected]> wrote:
>>> On Thu, Mar 29, 2012 at 6:14 PM, Richard Guenther
>>> <[email protected]> wrote:
>>>> On Thu, Mar 29, 2012 at 12:10 PM, Bin.Cheng <[email protected]> wrote:
>>>>> On Thu, Mar 29, 2012 at 6:07 PM, Richard Guenther
>>>>> <[email protected]> wrote:
>>>>>> On Thu, Mar 29, 2012 at 12:02 PM, Bin.Cheng <[email protected]>
>>>>>> wrote:
>>>>>>> Hi,
>>>>>>> Following is the tree dump of 094t.pre for a test program.
>>>>>>> Question is loads of D.5375_12/D.5375_14 are redundant on path <bb2,
>>>>>>> bb7, bb5, bb6>,
>>>>>>> but why not lowered into basic block 3, where it is used.
>>>>>>>
>>>>>>> BTW, seems no tree pass handles this case currently.
>>>>>>
>>>>>> tree-ssa-sink.c should do this.
>>>>>>
>>>>> It does not work for me, I will double check and update soon.
>>>>
>>>> Well, "should" as in, it's the place to do it. And certainly the pass can
>>>> sink
>>>> loads, so this must be a missed optimization.
>>>>
>>> Curiously, it is said explicitly that "We don't want to sink loads from
>>> memory."
>>> in tree-ssa-sink.c function statement_sink_location, and the condition is
>>>
>>> if (stmt_ends_bb_p (stmt)
>>> || gimple_has_side_effects (stmt)
>>> || gimple_has_volatile_ops (stmt)
>>> || (gimple_vuse (stmt) && !gimple_vdef (stmt))
>>> <-----------------check load
>>> || (cfun->has_local_explicit_reg_vars
>>> && TYPE_MODE (TREE_TYPE (gimple_assign_lhs (stmt))) == BLKmode))
>>> return false;
>>>
>>> I haven't found any clue about this decision in ChangeLogs.
>>
>> Ah, that's probably because usually you want to hoist loads and sink stores,
>> separating them (like a scheduler would do). We'd want to restrict sinking
>> of loads to sink into not post-dominated regions (thus where they end up
>> being executed less times).
Hi Richard,
I am testing a patch to sink load of memory to proper basic block.
Everything goes fine except auto-vectorization, sinking of load sometime
corrupts the canonical form of data references. I haven't touched auto-vec
before and cannot tell whether it's good or bad to do sink before auto-vec.
For example, the slp-cond-1.c
<bb 3>:
# i_39 = PHI <i_32(11), 0(2)>
D.5150_5 = i_39 * 2;
D.5151_10 = D.5150_5 + 1;
D.5153_17 = a[D.5150_5];
D.5154_19 = b[D.5150_5];
if (D.5153_17 >= D.5154_19)
goto <bb 9>;
else
goto <bb 4>;
<bb 9>:
d0_6 = d[D.5150_5]; <-----this is sunk from bb3
goto <bb 5>;
<bb 4>:
e0_8 = e[D.5150_5]; <-----this is sunk from bb3
<bb 5>:
# d0_2 = PHI <d0_6(9), e0_8(4)>
k[D.5150_5] = d0_2;
D.5159_26 = a[D.5151_10];
D.5160_29 = b[D.5151_10];
if (D.5159_26 >= D.5160_29)
goto <bb 10>;
else
goto <bb 6>;
<bb 10>:
d1_11 = d[D.5151_10]; <-----this is sunk from bb3
goto <bb 7>;
<bb 6>:
e1_14 = e[D.5151_10]; <-----this is sunk from bb3
<bb 7>:
.......
I will look into auto-vect but not sure how to handle this case.
Any comments? Thanks very much.
--
Best Regards.
