On Mon, Nov 25, 2013 at 10:08 AM, Diego Novillo <dnovi...@google.com> wrote:
> Thanks, Deaho.
>
> One other thing that I've found on the LLVM implementation (that I'm
> not sure happens in GCC): self-referential edges. If a loop consists
> of a single-basic block, the back edge will point to itself. I
> haven't been able to reproduce it with regular control flow constructs
> in GCC.
>
> When this happens, and if we've visited the block itself already
> (i.e., the block has weights), I've simply set the weight of the
> self-referential edge to the weight of the block itself. Do you see
> any problems with that heuristic?
In this case, the propagate_edge function will keep increasing the BB
count. We set a threshold (PARAM_AUTOFDO_MAX_PROPAGATE_ITERATIONS) to
prevent it from making BB count too large.
Dehao
>
>
> Thanks. Diego.
>
> On Mon, Nov 25, 2013 at 12:56 PM, Dehao Chen <de...@google.com> wrote:
>> afdo_propagate_multi_edge can do everything afdo_propagate_single_edge
>> does. So we refactor the code to keep only one afdo_propagate_edge
>> function.
>>
>> Bootstrapped and passed all unittests and performance tests.
>>
>> OK for googlge branch?
>>
>> Thanks,
>> Dehao
>>
>> Index: gcc/auto-profile.c
>> ===================================================================
>> --- gcc/auto-profile.c (revision 205354)
>> +++ gcc/auto-profile.c (working copy)
>> @@ -1069,44 +1069,6 @@ afdo_find_equiv_class (void)
>> }
>> }
>>
>> -/* If a baisk block only has one in/out edge, then the bb count and he
>> - edge count should be the same.
>> - IS_SUCC is true if the out edge of the basic block is examined.
>> - Return TRUE if any basic block/edge count is changed. */
>> -
>> -static bool
>> -afdo_propagate_single_edge (bool is_succ)
>> -{
>> - basic_block bb;
>> - bool changed = false;
>> -
>> - FOR_EACH_BB (bb)
>> - if (is_succ ? single_succ_p (bb) : single_pred_p (bb))
>> - {
>> - edge e = is_succ ? single_succ_edge (bb) : single_pred_edge (bb);
>> - if (((e->flags & EDGE_ANNOTATED) == 0)
>> - && ((bb->flags & BB_ANNOTATED) != 0))
>> - {
>> - e->count = bb->count;
>> - e->flags |= EDGE_ANNOTATED;
>> - changed = true;
>> - }
>> - else if (((e->flags & EDGE_ANNOTATED) != 0)
>> - && ((bb->flags & BB_ANNOTATED) == 0))
>> - {
>> - bb->count = e->count;
>> - bb->flags |= BB_ANNOTATED;
>> - changed = true;
>> - }
>> - else if (bb->count != e->count)
>> - {
>> - e->count = bb->count = MAX (bb->count, e->count);
>> - changed = true;
>> - }
>> - }
>> - return changed;
>> -}
>> -
>> /* If a basic block's count is known, and only one of its in/out edges'
>> count
>> is unknown, its count can be calculated.
>> Meanwhile, if all of the in/out edges' counts are known, then the basic
>> @@ -1115,7 +1077,7 @@ afdo_find_equiv_class (void)
>> Return TRUE if any basic block/edge count is changed. */
>>
>> static bool
>> -afdo_propagate_multi_edge (bool is_succ)
>> +afdo_propagate_edge (bool is_succ)
>> {
>> basic_block bb;
>> bool changed = false;
>> @@ -1281,14 +1243,10 @@ afdo_propagate (void)
>> {
>> changed = false;
>>
>> - if (afdo_propagate_single_edge (true))
>> + if (afdo_propagate_edge (true))
>> changed = true;
>> - if (afdo_propagate_single_edge (false))
>> + if (afdo_propagate_edge (false))
>> changed = true;
>> - if (afdo_propagate_multi_edge (true))
>> - changed = true;
>> - if (afdo_propagate_multi_edge (false))
>> - changed = true;
>> afdo_propagate_circuit ();
>> }
>> }
