OpenE2K/gcc
2
0
Fork 0
Code Issues Pull Requests Projects Releases Wiki Activity

tree-optimization/97623 - avoid excessive insert iteration for hoisting

Browse Source 
This avoids requiring insert iteration for back-to-back hoisting
opportunities as seen in the added testcase.  For the PR at hand
this halves the number of insert iterations retaining only
the hard to avoid PRE / hoist insert back-to-backs.

2020-10-30  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/97623
	* tree-ssa-pre.c (insert): First do hoist insertion in
	a backward walk.

	* gcc.dg/tree-ssa/ssa-hoist-7.c: New testcase.
This commit is contained in:
Richard Biener 2020-10-30 13:32:32 +01:00
parent 33c0f246f7
commit 82ff7e3426
2 changed files with 63 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

54
gcc/testsuite/gcc.dg/tree-ssa/ssa-hoist-7.c Normal file
View File

@ -0,0 +1,54 @@
/* { dg-options "-O2 -fdump-tree-pre-stats" } */
void baz();
int tem;
void foo (int a, int b, int c, int d, int e, int x, int y, int z)
{
if (a)
{
if (b)
{
if (c)
{
if (d)
{
if (e)
{
tem = x + y;
}
else
{
if (z) baz ();
tem = x + y;
}
}
else
{
if (z) baz ();
tem = x + y;
}
}
else
{
if (z) baz ();
tem = x + y;
}
}
else
{
if (z) baz ();
tem = x + y;
}
}
else
{
if (z) baz ();
tem = x + y;
}
}
/* Now inserting x + y five times is unnecessary but the cascading
cannot be avoided with the simple-minded dataflow. But make sure
we do the insertions all in the first iteration. */
/* { dg-final { scan-tree-dump "insert iterations == 2" "pre" } } */
/* { dg-final { scan-tree-dump "HOIST inserted: 5" "pre" } } */

13
gcc/tree-ssa-pre.c
View File

@ -3646,6 +3646,15 @@ insert (void)
fprintf (dump_file, "Starting insert iteration %d\n", num_iterations);
changed = false;
/* Insert expressions for hoisting. Do a backward walk here since
inserting into BLOCK exposes new opportunities in its predecessors. */
if (flag_code_hoisting)
for (int idx = rpo_num - 1; idx >= 0; --idx)
{
basic_block block = BASIC_BLOCK_FOR_FN (cfun, rpo[idx]);
if (EDGE_COUNT (block->succs) >= 2)
changed |= do_hoist_insertion (block);
}
for (int idx = 0; idx < rpo_num; ++idx)
{
basic_block block = BASIC_BLOCK_FOR_FN (cfun, rpo[idx]);
@ -3680,10 +3689,6 @@ insert (void)
if (do_partial_partial)
changed |= do_pre_partial_partial_insertion (block, dom);
}
/* Insert expressions for hoisting. */
if (flag_code_hoisting && EDGE_COUNT (block->succs) >= 2)
changed |= do_hoist_insertion (block);
}
}