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6591247: C2 cleans up the merge point too early during SplitIf

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Remove region self reference last

Reviewed-by: kvn, never
This commit is contained in:
Igor Veresov 2011-08-27 00:23:47 -07:00
parent 6446205688
commit ec3f90d1b4
1 changed files with 18 additions and 21 deletions
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39
hotspot/src/share/vm/opto/split_if.cpp
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@ -500,19 +500,14 @@ void PhaseIdealLoop::do_split_if( Node *iff ) {
region_cache.lru_insert( new_false, new_false );
region_cache.lru_insert( new_true , new_true );
// Now handle all uses of the splitting block
for (DUIterator_Last kmin, k = region->last_outs(kmin); k >= kmin; --k) {
Node* phi = region->last_out(k);
if( !phi->in(0) ) { // Dead phi? Remove it
for (DUIterator k = region->outs(); region->has_out(k); k++) {
Node* phi = region->out(k);
if (!phi->in(0)) { // Dead phi? Remove it
_igvn.remove_dead_node(phi);
continue;
}
assert( phi->in(0) == region, "" );
if( phi == region ) { // Found the self-reference
phi->set_req(0, NULL);
continue; // Break the self-cycle
}
// Expected common case: Phi hanging off of Region
if( phi->is_Phi() ) {
} else if (phi == region) { // Found the self-reference
continue; // No roll-back of DUIterator
} else if (phi->is_Phi()) { // Expected common case: Phi hanging off of Region
assert(phi->in(0) == region, "Inconsistent graph");
// Need a per-def cache. Phi represents a def, so make a cache
small_cache phi_cache;
@ -524,23 +519,25 @@ void PhaseIdealLoop::do_split_if( Node *iff ) {
// collection of PHI's merging values from different paths. The Phis
// inserted depend only on the location of the USE. We use a
// 2-element cache to handle multiple uses from the same block.
handle_use( use, phi, &phi_cache, region_dom, new_false, new_true, old_false, old_true );
handle_use(use, phi, &phi_cache, region_dom, new_false, new_true, old_false, old_true);
} // End of while phi has uses
// Because handle_use might relocate region->_out,
// we must refresh the iterator.
k = region->last_outs(kmin);
// Remove the dead Phi
_igvn.remove_dead_node( phi );
} else {
assert(phi->in(0) == region, "Inconsistent graph");
// Random memory op guarded by Region. Compute new DEF for USE.
handle_use( phi, region, &region_cache, region_dom, new_false, new_true, old_false, old_true );
handle_use(phi, region, &region_cache, region_dom, new_false, new_true, old_false, old_true);
}
// Every path above deletes a use of the region, except for the region
// self-cycle (which is needed by handle_use calling find_use_block
// calling get_ctrl calling get_ctrl_no_update looking for dead
// regions). So roll back the DUIterator innards.
--k;
} // End of while merge point has phis
assert(region->outcnt() == 1, "Only self reference should remain"); // Just Self on the Region
region->set_req(0, NULL); // Break the self-cycle
// Any leftover bits in the splitting block must not have depended on local
// Phi inputs (these have already been split-up). Hence it's safe to hoist
// these guys to the dominating point.