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comparison src/share/vm/opto/split_if.cpp @ 3893:8805f8c1e23e

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6591247: C2 cleans up the merge point too early during SplitIf Summary: Remove region self reference last Reviewed-by: kvn, never
author iveresov
date Sat, 27 Aug 2011 00:23:47 -0700
parents 08eb13460b3a
children 5e990493719e
comparison
equal deleted inserted replaced
3892:baf763f388e6 3893:8805f8c1e23e
498 small_cache region_cache; 498 small_cache region_cache;
499 // Preload some control flow in region-cache 499 // Preload some control flow in region-cache
500 region_cache.lru_insert( new_false, new_false ); 500 region_cache.lru_insert( new_false, new_false );
501 region_cache.lru_insert( new_true , new_true ); 501 region_cache.lru_insert( new_true , new_true );
502 // Now handle all uses of the splitting block 502 // Now handle all uses of the splitting block
503 for (DUIterator_Last kmin, k = region->last_outs(kmin); k >= kmin; --k) { 503 for (DUIterator k = region->outs(); region->has_out(k); k++) {
504 Node* phi = region->last_out(k); 504 Node* phi = region->out(k);
505 if( !phi->in(0) ) { // Dead phi? Remove it 505 if (!phi->in(0)) { // Dead phi? Remove it
506 _igvn.remove_dead_node(phi); 506 _igvn.remove_dead_node(phi);
507 continue; 507 } else if (phi == region) { // Found the self-reference
508 } 508 continue; // No roll-back of DUIterator
509 assert( phi->in(0) == region, "" ); 509 } else if (phi->is_Phi()) { // Expected common case: Phi hanging off of Region
510 if( phi == region ) { // Found the self-reference 510 assert(phi->in(0) == region, "Inconsistent graph");
511 phi->set_req(0, NULL);
512 continue; // Break the self-cycle
513 }
514 // Expected common case: Phi hanging off of Region
515 if( phi->is_Phi() ) {
516 // Need a per-def cache. Phi represents a def, so make a cache 511 // Need a per-def cache. Phi represents a def, so make a cache
517 small_cache phi_cache; 512 small_cache phi_cache;
518 513
519 // Inspect all Phi uses to make the Phi go dead 514 // Inspect all Phi uses to make the Phi go dead
520 for (DUIterator_Last lmin, l = phi->last_outs(lmin); l >= lmin; --l) { 515 for (DUIterator_Last lmin, l = phi->last_outs(lmin); l >= lmin; --l) {
522 // Compute the new DEF for this USE. New DEF depends on the path 517 // Compute the new DEF for this USE. New DEF depends on the path
523 // taken from the original DEF to the USE. The new DEF may be some 518 // taken from the original DEF to the USE. The new DEF may be some
524 // collection of PHI's merging values from different paths. The Phis 519 // collection of PHI's merging values from different paths. The Phis
525 // inserted depend only on the location of the USE. We use a 520 // inserted depend only on the location of the USE. We use a
526 // 2-element cache to handle multiple uses from the same block. 521 // 2-element cache to handle multiple uses from the same block.
527 handle_use( use, phi, &phi_cache, region_dom, new_false, new_true, old_false, old_true ); 522 handle_use(use, phi, &phi_cache, region_dom, new_false, new_true, old_false, old_true);
528 } // End of while phi has uses 523 } // End of while phi has uses
529
530 // Because handle_use might relocate region->_out,
531 // we must refresh the iterator.
532 k = region->last_outs(kmin);
533
534 // Remove the dead Phi 524 // Remove the dead Phi
535 _igvn.remove_dead_node( phi ); 525 _igvn.remove_dead_node( phi );
536
537 } else { 526 } else {
527 assert(phi->in(0) == region, "Inconsistent graph");
538 // Random memory op guarded by Region. Compute new DEF for USE. 528 // Random memory op guarded by Region. Compute new DEF for USE.
539 handle_use( phi, region, &region_cache, region_dom, new_false, new_true, old_false, old_true ); 529 handle_use(phi, region, &region_cache, region_dom, new_false, new_true, old_false, old_true);
540 } 530 }
541 531 // Every path above deletes a use of the region, except for the region
532 // self-cycle (which is needed by handle_use calling find_use_block
533 // calling get_ctrl calling get_ctrl_no_update looking for dead
534 // regions). So roll back the DUIterator innards.
535 --k;
542 } // End of while merge point has phis 536 } // End of while merge point has phis
537
538 assert(region->outcnt() == 1, "Only self reference should remain"); // Just Self on the Region
539 region->set_req(0, NULL); // Break the self-cycle
543 540
544 // Any leftover bits in the splitting block must not have depended on local 541 // Any leftover bits in the splitting block must not have depended on local
545 // Phi inputs (these have already been split-up). Hence it's safe to hoist 542 // Phi inputs (these have already been split-up). Hence it's safe to hoist
546 // these guys to the dominating point. 543 // these guys to the dominating point.
547 lazy_replace( region, region_dom ); 544 lazy_replace( region, region_dom );