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tree-optimization/116460 - improve forwprop compile-time

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The following improves forwprop block reachability which I noticed
when debugging PR116460 and what is also noted in the comment.  It
avoids processing blocks in natural loops determined unreachable,
thereby making the issue in PR116460 latent.

	PR tree-optimization/116460
	* tree-ssa-forwprop.cc (pass_forwprop::execute): Do not
	process blocks in unreachable natural loops.
This commit is contained in:
Richard Biener 2024-08-26 10:01:44 +02:00 • committed by Richard Biener
parent 03b802e14f
commit 0ceeb9926d
1 changed files with 7 additions and 6 deletions
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13
gcc/tree-ssa-forwprop.cc
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@ -3498,6 +3498,8 @@ pass_forwprop::execute (function *fun)
cfg_changed = false;
calculate_dominance_info (CDI_DOMINATORS);
/* Combine stmts with the stmts defining their operands. Do that
in an order that guarantees visiting SSA defs before SSA uses. */
lattice.create (num_ssa_names);
@ -3537,12 +3539,11 @@ pass_forwprop::execute (function *fun)
FOR_EACH_EDGE (e, ei, bb->preds)
{
if ((e->flags & EDGE_EXECUTABLE)
/* With dominators we could improve backedge handling
when e->src is dominated by bb. But for irreducible
regions we have to take all backedges conservatively.
We can handle single-block cycles as we know the
dominator relationship here. */
|| bb_to_rpo[e->src->index] > i)
/* We can handle backedges in natural loops correctly but
for irreducible regions we have to take all backedges
conservatively when we did not visit the source yet. */
|| (bb_to_rpo[e->src->index] > i
&& !dominated_by_p (CDI_DOMINATORS, e->src, e->dest)))
{
any = true;
break;