On Wed, Jul 4, 2012 at 8:07 PM, Tom de Vries <tom_devr...@mentor.com> wrote:
> On 31/01/12 22:07, Tom de Vries wrote:
>> On 31/01/12 22:05, Tom de Vries wrote:
>>> Richard,
>>>
>>
>> Sorry, with patch this time.
>>
>>> this patch fixes PR52009.
>>>
>>> Consider this test-case:
>>> ...
>>> int z;
>>>
>>> void
>>> foo (int y)
>>> {
>>> if (y == 6)
>>> z = 5;
>>> else
>>> z = 5;
>>> }
>>> ...
>>>
>>> Currently, compiling with -O2 gives us this representation at
>>> pr51879-7.c.094t.pre:
>>> ...
>>> # BLOCK 3 freq:1991
>>> # PRED: 2 [19.9%] (true,exec)
>>> # .MEMD.1710_4 = VDEF <.MEMD.1710_3(D)>
>>> zD.1702 = 5;
>>> goto <bb 5>;
>>> # SUCC: 5 [100.0%] (fallthru,exec)
>>>
>>> # BLOCK 4 freq:8009
>>> # PRED: 2 [80.1%] (false,exec)
>>> # .MEMD.1710_5 = VDEF <.MEMD.1710_3(D)>
>>> zD.1702 = 5;
>>> # SUCC: 5 [100.0%] (fallthru,exec)
>>>
>>> # BLOCK 5 freq:10000
>>> # PRED: 3 [100.0%] (fallthru,exec) 4 [100.0%] (fallthru,exec)
>>> # .MEMD.1710_2 = PHI <.MEMD.1710_4(3), .MEMD.1710_5(4)>
>>> # VUSE <.MEMD.1710_2>
>>> return;
>>> ...
>>>
>>> Blocks 3 and 4 are not tail-merged.
>>>
>>> The patch allows the example to be tail-merged by:
>>> - value numbering .MEMD.1710_4 and .MEMD.1710_5 equal
>>> - comparing gimple_vdef value numbers for assignments during tail-merge
>>>
>>> Bootstrapped and reg-tested on x86_64.
>>>
>>> OK for stage1?
>>>
>
> Richard,
>
> I did some trivial changes such that the patch is applicable again to trunk,
> and
> added a test-case, which you suggested in
> http://gcc.gnu.org/ml/gcc-patches/2012-05/msg00220.html.
>
> The test-case handles the case of 2 identical calls assigning to different
> deferenced pointers, where the pointers are value-numbered the same:
> ...
> void bar (int c, int *p)
> {
> int *q = p;
>
> if (c)
> *p = foo ();
> else
> *q = foo ();
> }
> ...
>
> The representation before pre looks like this:
> ...
> # BLOCK 3 freq:3900
> # PRED: 2 [39.0%] (true,exec)
> # .MEMD.1724_8 = VDEF <.MEMD.1724_7(D)>
> # USE = nonlocal
> # CLB = nonlocal
> D.1721_4 = fooD.1712 ();
> # .MEMD.1724_9 = VDEF <.MEMD.1724_8>
> *pD.1714_1(D) = D.1721_4;
> goto <bb 5>;
> # SUCC: 5 [100.0%] (fallthru,exec)
>
> # BLOCK 4 freq:6100
> # PRED: 2 [61.0%] (false,exec)
> # .MEMD.1724_10 = VDEF <.MEMD.1724_7(D)>
> # USE = nonlocal
> # CLB = nonlocal
> D.1723_5 = fooD.1712 ();
> # .MEMD.1724_11 = VDEF <.MEMD.1724_10>
> *qD.1717_2 = D.1723_5;
> # SUCC: 5 [100.0%] (fallthru,exec)
> ...
>
> In pre, we're already value numbering the result and vdef of the calls the
> same,
> and the pointers the same:
> ...
> Value numbers:
> q_2 = p_1(D)
> D.1723_5 = D.1721_4
> .MEM_10 = .MEM_8
> ...
>
> But not the vdefs of the stores. This patch implements that, and allows the
> blocks to be merged.
>
> ok for trunk?
Ok.
Thanks,
Richard.
> Thanks,
> - Tom
>
> 2012-07-04 Tom de Vries <t...@codesourcery.com>
>
> PR tree-optimization/52009
> * tree-ssa-tail-merge.c (gimple_equal_p): For GIMPLE_ASSIGN, compare
> value numbers of gimple_vdef.
> * tree-ssa-sccvn.h (vn_reference_insert): Add vdef parameter to
> prototype.
> * tree-ssa-sccvn.c (copy_reference_ops_from_ref): Handle MODIFY_EXPR.
> (vn_reference_insert): Add and handle vdef parameter.
> (visit_reference_op_load): Add argument to vn_reference_insert call.
> (visit_reference_op_store): Find value number of vdef of store.
> Insert
> value number of vdef of store.
>
> * gcc.dg/pr51879-7.c: New test.
> * gcc.dg/pr51879-18.c: New test.
