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Track arguments pointing to local or readonly memory in ipa-fnsummary

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this patch implement tracking wehther argument points to readonly memory. This
is is useful for ipa-modref as well as for inline heuristics.  It is desirable
to inline functions that dereference pointers to local variables in order
to support SRA.  We always did the oposite heuristics (guessing that the
dereferences will be optimized out with 50% probability) but here we could
increase the probability for cases where we can track that argument is indeed
a local memory (or readonly which is also good)

	* ipa-fnsummary.c (dump_ipa_call_summary): Dump
	points_to_local_or_readonly_memory flag.
	(analyze_function_body): Compute points_to_local_or_readonly_memory
	flag.
	(remap_edge_change_prob): Rename to ...
	(remap_edge_params): ... this one; update
	points_to_local_or_readonly_memory.
	(remap_edge_summaries): Update.
	(read_ipa_call_summary): Stream the new flag.
	(write_ipa_call_summary): Likewise.
	* ipa-predicate.h (struct inline_param_summary): Add
	points_to_local_or_readonly_memory.
	(inline_param_summary::equal_to): Update.
	(inline_param_summary::useless_p): Update.
This commit is contained in:
Jan Hubicka 2020-09-26 08:12:44 +02:00
parent 5a90a18668
commit b89e455995
2 changed files with 42 additions and 11 deletions
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43
gcc/ipa-fnsummary.c
View File

@ -980,6 +980,9 @@ dump_ipa_call_summary (FILE *f, int indent, struct cgraph_node *node,
else if (prob != REG_BR_PROB_BASE)
fprintf (f, "%*s op%i change %f%% of time\n", indent + 2, "", i,
prob * 100.0 / REG_BR_PROB_BASE);
if (es->param[i].points_to_local_or_readonly_memory)
fprintf (f, "%*s op%i points to local or readonly memory\n",
indent + 2, "", i);
}
if (!edge->inline_failed)
{
@ -2671,6 +2674,9 @@ analyze_function_body (struct cgraph_node *node, bool early)
int prob = param_change_prob (&fbi, stmt, i);
gcc_assert (prob >= 0 && prob <= REG_BR_PROB_BASE);
es->param[i].change_prob = prob;
es->param[i].points_to_local_or_readonly_memory
= points_to_local_or_readonly_memory_p
(gimple_call_arg (stmt, i));
}
}
@ -3781,15 +3787,17 @@ inline_update_callee_summaries (struct cgraph_node *node, int depth)
ipa_call_summaries->get (e)->loop_depth += depth;
}
/* Update change_prob of EDGE after INLINED_EDGE has been inlined.
/* Update change_prob and points_to_local_or_readonly_memory of EDGE after
INLINED_EDGE has been inlined.
When function A is inlined in B and A calls C with parameter that
changes with probability PROB1 and C is known to be passthrough
of argument if B that change with probability PROB2, the probability
of change is now PROB1*PROB2. */
static void
remap_edge_change_prob (struct cgraph_edge *inlined_edge,
struct cgraph_edge *edge)
remap_edge_params (struct cgraph_edge *inlined_edge,
struct cgraph_edge *edge)
{
if (ipa_node_params_sum)
{
@ -3823,7 +3831,16 @@ remap_edge_change_prob (struct cgraph_edge *inlined_edge,
prob = 1;
es->param[i].change_prob = prob;
if (inlined_es
->param[id].points_to_local_or_readonly_memory)
es->param[i].points_to_local_or_readonly_memory = true;
}
if (!es->param[i].points_to_local_or_readonly_memory
&& jfunc->type == IPA_JF_CONST
&& points_to_local_or_readonly_memory_p
(ipa_get_jf_constant (jfunc)))
es->param[i].points_to_local_or_readonly_memory = true;
}
}
}
@ -3856,7 +3873,7 @@ remap_edge_summaries (struct cgraph_edge *inlined_edge,
if (e->inline_failed)
{
class ipa_call_summary *es = ipa_call_summaries->get (e);
remap_edge_change_prob (inlined_edge, e);
remap_edge_params (inlined_edge, e);
if (es->predicate)
{
@ -3882,7 +3899,7 @@ remap_edge_summaries (struct cgraph_edge *inlined_edge,
predicate p;
next = e->next_callee;
remap_edge_change_prob (inlined_edge, e);
remap_edge_params (inlined_edge, e);
if (es->predicate)
{
p = es->predicate->remap_after_inlining
@ -4208,12 +4225,19 @@ read_ipa_call_summary (class lto_input_block *ib, struct cgraph_edge *e,
{
es->param.safe_grow_cleared (length, true);
for (i = 0; i < length; i++)
es->param[i].change_prob = streamer_read_uhwi (ib);
{
es->param[i].change_prob = streamer_read_uhwi (ib);
es->param[i].points_to_local_or_readonly_memory
= streamer_read_uhwi (ib);
}
}
else
{
for (i = 0; i < length; i++)
streamer_read_uhwi (ib);
{
streamer_read_uhwi (ib);
streamer_read_uhwi (ib);
}
}
}
@ -4438,7 +4462,10 @@ write_ipa_call_summary (struct output_block *ob, struct cgraph_edge *e)
streamer_write_uhwi (ob, 0);
streamer_write_uhwi (ob, es->param.length ());
for (i = 0; i < (int) es->param.length (); i++)
streamer_write_uhwi (ob, es->param[i].change_prob);
{
streamer_write_uhwi (ob, es->param[i].change_prob);
streamer_write_uhwi (ob, es->param[i].points_to_local_or_readonly_memory);
}
}

10
gcc/ipa-predicate.h
View File

@ -76,14 +76,18 @@ struct inline_param_summary
parameters REG_BR_PROB_BASE.
Value 0 is reserved for compile time invariants. */
int change_prob;
short change_prob;
unsigned points_to_local_or_readonly_memory : 1;
bool equal_to (const inline_param_summary &other) const
{
return change_prob == other.change_prob;
return change_prob == other.change_prob
&& points_to_local_or_readonly_memory
== other.points_to_local_or_readonly_memory;
}
bool useless_p (void) const
{
return change_prob == REG_BR_PROB_BASE;
return change_prob == REG_BR_PROB_BASE
&& !points_to_local_or_readonly_memory;
}
};