On Tue, Aug 16, 2016 at 9:45 AM, kugan
<[email protected]> wrote:
> Hi Richard,
>
> On 12/08/16 20:43, Richard Biener wrote:
>>
>> On Wed, Aug 3, 2016 at 3:17 AM, kugan <[email protected]>
>> wrote:
>
>
> [SNIP]
>
>>
>> diff --git a/gcc/common.opt b/gcc/common.opt
>> index 8a292ed..7028cd4 100644
>> --- a/gcc/common.opt
>> +++ b/gcc/common.opt
>> @@ -2482,6 +2482,10 @@ ftree-vrp
>> Common Report Var(flag_tree_vrp) Init(0) Optimization
>> Perform Value Range Propagation on trees.
>>
>> +fdisable-tree-evrp
>> +Common Report Var(flag_disable_early_vrp) Init(0) Optimization
>> +Disable Early Value Range Propagation on trees.
>> +
>>
>> no please, this is automatically supported via -fdisable-
>
>
> I am now having -ftree-evrp which is enabled all the time. But This will
> only be used for disabling the early-vrp. That is, early-vrp will be run
> when ftree-vrp is enabled and ftree-evrp is not explicitly disabled. Is this
> OK?
Why would one want to disable early-vrp? I see you do this in the testsuite
for non-early VRP unit-tests but using -fdisable-tree-evrp1 there
would be ok as well.
>>
>> @@ -1728,11 +1736,12 @@ extract_range_from_assert (value_range *vr_p, tree
>> expr)
>> always false. */
>>
>> static void
>> -extract_range_from_ssa_name (value_range *vr, tree var)
>> +extract_range_from_ssa_name (value_range *vr, bool dom_p, tree var)
>> {
>> value_range *var_vr = get_value_range (var);
>>
>> - if (var_vr->type != VR_VARYING)
>> + if (var_vr->type != VR_VARYING
>> + && (!dom_p || var_vr->type != VR_UNDEFINED))
>> copy_value_range (vr, var_vr);
>> else
>> set_value_range (vr, VR_RANGE, var, var, NULL);
>>
>> why do you need these changes? I think I already told you you need to
>> initialize the lattice to sth else than VR_UNDEFINED and that you can't
>> fully re-use update_value_range. If you don't want to do that then
>> instead
>> of doing changes all over the place do it in get_value_range and have a
>> global flag.
>
>
> I have now added a global early_vrp_p and use this to initialize
> VR_INITIALIZER and get_value_range default to VR_VARYING.
ICK. Ok, I see that this works, but it is quite ugly, so (see below)
>>
>>
>> @@ -3594,7 +3643,8 @@ extract_range_from_cond_expr (value_range *vr,
>> gassign *stmt)
>> on the range of its operand and the expression code. */
>>
>> static void
>> -extract_range_from_comparison (value_range *vr, enum tree_code code,
>> +extract_range_from_comparison (value_range *vr,
>> + enum tree_code code,
>> tree type, tree op0, tree op1)
>> {
>> bool sop = false;
>>
>> remove these kind of no-op changes.
>
>
> Done.
>
>
>>
>> +/* Initialize local data structures for VRP. If DOM_P is true,
>> + we will be calling this from early_vrp where value range propagation
>> + is done by visiting stmts in dominator tree. ssa_propagate engine
>> + is not used in this case and that part of the ininitialization will
>> + be skipped. */
>>
>> static void
>> -vrp_initialize (void)
>> +vrp_initialize (bool dom_p)
>> {
>> basic_block bb;
>>
>> @@ -6949,6 +7010,9 @@ vrp_initialize (void)
>> vr_phi_edge_counts = XCNEWVEC (int, num_ssa_names);
>> bitmap_obstack_initialize (&vrp_equiv_obstack);
>>
>> + if (dom_p)
>> + return;
>> +
>>
>> split the function instead.
>>
>> @@ -7926,7 +7992,8 @@ vrp_visit_switch_stmt (gswitch *stmt, edge
>> *taken_edge_p)
>> If STMT produces a varying value, return SSA_PROP_VARYING. */
>>
>> static enum ssa_prop_result
>> -vrp_visit_stmt (gimple *stmt, edge *taken_edge_p, tree *output_p)
>> +vrp_visit_stmt_worker (gimple *stmt, bool dom_p, edge *taken_edge_p,
>> + tree *output_p)
>> {
>> tree def;
>> ssa_op_iter iter;
>> @@ -7940,7 +8007,7 @@ vrp_visit_stmt (gimple *stmt, edge
>> *taken_edge_p, tree *output_p)
>> if (!stmt_interesting_for_vrp (stmt))
>> gcc_assert (stmt_ends_bb_p (stmt));
>> else if (is_gimple_assign (stmt) || is_gimple_call (stmt))
>> - return vrp_visit_assignment_or_call (stmt, output_p);
>> + return vrp_visit_assignment_or_call (stmt, dom_p, output_p);
>> else if (gimple_code (stmt) == GIMPLE_COND)
>> return vrp_visit_cond_stmt (as_a <gcond *> (stmt), taken_edge_p);
>> else if (gimple_code (stmt) == GIMPLE_SWITCH)
>> @@ -7954,6 +8021,12 @@ vrp_visit_stmt (gimple *stmt, edge
>> *taken_edge_p, tree *output_p)
>> return SSA_PROP_VARYING;
>> }
>>
>> +static enum ssa_prop_result
>> +vrp_visit_stmt (gimple *stmt, edge *taken_edge_p, tree *output_p)
>> +{
>> + return vrp_visit_stmt_worker (stmt, false, taken_edge_p, output_p);
>> +}
>>
>> as said the refactoring that would be appreciated is to split out the
>> update_value_range calls
>> from the worker functions so you can call the respective functions
>> from the DOM implementations.
>> That they are globbed in vrp_visit_stmt currently is due to the API of
>> the SSA propagator.
>
> Sent this as separate patch for easy reviewing and testing.
Thanks.
>>
>> @@ -8768,6 +8842,12 @@ vrp_visit_phi_node (gphi *phi)
>> fprintf (dump_file, "\n");
>> }
>>
>> + if (dom_p && vr_arg.type == VR_UNDEFINED)
>> + {
>> + set_value_range_to_varying (&vr_result);
>> + break;
>> + }
>> +
>>
>> eh... ok, so another way to attack this is, instead of initializing
>> the lattice to sth else
>> than VR_UNDEFINED, make sure to drop the lattice to varying for all PHI
>> args on
>> yet unvisited incoming edges (you're not doing optimistic VRP). That's
>> the only
>> place you _have_ to do it.
>
>
> Even when it is initialize (as I am doing now), we can still end up with
> VR_UNDEFINED during the propagation. I have just left the above so that we
> dont end up with the wrong VR.
How would we end up with wrong VRs? I see
+ /* Discover VR when condition is true. */
+ extract_range_for_var_from_comparison_expr (op0, code, op0, op1, &vr);
+ if (old_vr->type == VR_RANGE || old_vr->type == VR_ANTI_RANGE)
+ vrp_intersect_ranges (&vr, old_vr);
where you already disregard UNDEFINED as old_vr.
What you might be missing is to set all DEFs on !stmt_interesting_for_vrp to
VARYING. Also
+ if (stmt_interesting_for_vrp (stmt))
+ {
+ tree lhs = gimple_get_lhs (stmt);
+ value_range vr = VR_INITIALIZER;
+ vrp_visit_stmt_worker (stmt, &taken_edge, &output, &vr);
+ update_value_range (lhs, &vr);
+
+ /* Try folding stmts with the VR discovered. */
+ if (fold_stmt (&gsi, follow_single_use_edges))
+ update_stmt (gsi_stmt (gsi));
folding here can introduce additional stmts and thus unvisited SSA defs
which would end up with VR_UNINITIALIZED defs - I don't see exactly
where that would cause issues but I'm not sure it might not. So better
use fold_stmt_inplace or alternatively if fold_stmt returned true then,
remembering the previous stmt gsi, iterate over all stmts emitted and
set their defs to varying (or re-visit them). See for example how
tree-ssa-forwprop.c does this re-visiting (it revisits all changed stmts).
Note that you want to have a custom valueize function instead of just
follow_single_use_edges as you want to valueize all SSA names according
to their lattice value (if it has a single value). You can use vrp_valueize
for this though that gets you non-single-use edge following as well.
Eventually it's going to be cleaner to do what the SSA propagator does and
before folding do
did_replace = replace_uses_in (stmt, vrp_valueize);
if (fold_stmt (&gsi, follow_single_use_edges)
|| did_replace)
update_stmt (gsi_stmt (gsi));
exporting replace_uses_in for this is ok. I guess I prefer this for now.
Overall this now looks good apart from the folding and the VR_INITIALIZER thing.
You can commit the already approved refactoring changes and combine this
patch with the struct value_range move, this way I can more easily look into
issues with the UNDEFINED thing if you can come up with a testcase that
doesn't work.
Thanks,
Richard.
> I also noticed that g++.dg/warn/pr33738.C testcase is now failing. This is
> because, with early-vrp setting value range ccp2 is optimizing without
> issuing a warning. I will look into it.
>
> bootstrap and regression testing is in progress.
>
> Thanks,
> Kugan
