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Speedup PTA solving for call constraint sets

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With calls we now often get contraints like

  callarg = *callarg + UNKNOWN

or similar cases.  The important thing to note is that this
complex constraint changes the node solution itself, so when
solving the node is marked as changed immediately again.  When
that happens it's profitable to iterate that self-cycle immediately
so we maximize cache reuse and build up the successor graph quickly
to get better topological ordering and reduce the number of
iterations of the solving.

For a testcase derived from ceph this reduces the time spent in
PTA solving from 453s to 92s which is quite significant.

	* tree-ssa-structalias.cc (solve_graph): Immediately
	iterate self-cycles.
This commit is contained in:
Richard Biener
2023-03-10 14:15:14 +01:00
parent 649f1939ba
commit 413ec1d12c
1 changed files with 11 additions and 4 deletions
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gcc/tree-ssa-structalias.cc
+11 -4
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@@ -2775,8 +2775,15 @@ solve_graph (constraint_graph_t graph)
continue;
/* If the node has changed, we need to process the
complex constraints and outgoing edges again. */
if (bitmap_clear_bit (changed, i))
complex constraints and outgoing edges again. For complex
constraints that modify i itself, like the common group of
callarg = callarg + UNKNOWN;
callarg = *callarg + UNKNOWN;
*callarg = callescape;
make sure to iterate immediately because that maximizes
cache reuse and expands the graph quickest, leading to
better visitation order in the next iteration. */
while (bitmap_clear_bit (changed, i))
{
unsigned int j;
constraint_t c;
@@ -2794,7 +2801,7 @@ solve_graph (constraint_graph_t graph)
??? But we shouldn't ended up with "changed" set ... */
if (vi->oldsolution
&& bitmap_bit_p (vi->oldsolution, anything_id))
continue;
break;
bitmap_copy (pts, get_varinfo (find (anything_id))->solution);
}
else if (vi->oldsolution)
@@ -2803,7 +2810,7 @@ solve_graph (constraint_graph_t graph)
bitmap_copy (pts, vi->solution);
if (bitmap_empty_p (pts))
continue;
break;
if (vi->oldsolution)
bitmap_ior_into (vi->oldsolution, pts);