jdk8-mips64-public/hotspot: src/share/vm/opto/split

src/share/vm/opto/split_if.cpp@98cb887364d3 (annotated)

src/share/vm/opto/split_if.cpp

Fri, 27 Feb 2009 13:27:09 -0800

author: twisti
date: Fri, 27 Feb 2009 13:27:09 -0800
changeset 1040: 98cb887364d3
parent 435: a61af66fc99e
child 1607: b2b6a9bf6238
permissions: -rw-r--r--

6810672: Comment typos
Summary: I have collected some typos I have found while looking at the code.
Reviewed-by: kvn, never

 /*
  * Copyright 1999-2006 Sun Microsystems, Inc.  All Rights Reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
  * under the terms of the GNU General Public License version 2 only, as
  * published by the Free Software Foundation.
  *
  * This code is distributed in the hope that it will be useful, but WITHOUT
  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  * version 2 for more details (a copy is included in the LICENSE file that
  * accompanied this code).
  *
  * You should have received a copy of the GNU General Public License version
  * 2 along with this work; if not, write to the Free Software Foundation,
  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  *
  * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
  * CA 95054 USA or visit www.sun.com if you need additional information or
  * have any questions.
  *
  */
 #include "incls/_precompiled.incl"
 #include "incls/_split_if.cpp.incl"
 //------------------------------split_thru_region------------------------------
 // Split Node 'n' through merge point.
 Node *PhaseIdealLoop::split_thru_region( Node *n, Node *region ) {
   uint wins = 0;
   assert( n->is_CFG(), "" );
   assert( region->is_Region(), "" );
   Node *r = new (C, region->req()) RegionNode( region->req() );
   IdealLoopTree *loop = get_loop( n );
   for( uint i = 1; i < region->req(); i++ ) {
     Node *x = n->clone();
     Node *in0 = n->in(0);
     if( in0->in(0) == region ) x->set_req( 0, in0->in(i) );
     for( uint j = 1; j < n->req(); j++ ) {
       Node *in = n->in(j);
       if( get_ctrl(in) == region )
         x->set_req( j, in->in(i) );
     }
     _igvn.register_new_node_with_optimizer(x);
     set_loop(x, loop);
     set_idom(x, x->in(0), dom_depth(x->in(0))+1);
     r->init_req(i, x);
   }
   // Record region
   r->set_req(0,region);         // Not a TRUE RegionNode
   _igvn.register_new_node_with_optimizer(r);
   set_loop(r, loop);
   if( !loop->_child )
     loop->_body.push(r);
   return r;
 }
 //------------------------------split_up---------------------------------------
 // Split block-local op up through the phis to empty the current block
 bool PhaseIdealLoop::split_up( Node *n, Node *blk1, Node *blk2 ) {
   if( n->is_CFG() ) {
     assert( n->in(0) != blk1, "Lousy candidate for split-if" );
     return false;
   }
   if( get_ctrl(n) != blk1 && get_ctrl(n) != blk2 )
     return false;               // Not block local
   if( n->is_Phi() ) return false; // Local PHIs are expected
   // Recursively split-up inputs
   for (uint i = 1; i < n->req(); i++) {
     if( split_up( n->in(i), blk1, blk2 ) ) {
       // Got split recursively and self went dead?
       if (n->outcnt() == 0)
         _igvn.remove_dead_node(n);
       return true;
     }
   }
   // Check for needing to clone-up a compare.  Can't do that, it forces
   // another (nested) split-if transform.  Instead, clone it "down".
   if( n->is_Cmp() ) {
     assert(get_ctrl(n) == blk2 || get_ctrl(n) == blk1, "must be in block with IF");
     // Check for simple Cmp/Bool/CMove which we can clone-up.  Cmp/Bool/CMove
     // sequence can have no other users and it must all reside in the split-if
     // block.  Non-simple Cmp/Bool/CMove sequences are 'cloned-down' below -
     // private, per-use versions of the Cmp and Bool are made.  These sink to
     // the CMove block.  If the CMove is in the split-if block, then in the
     // next iteration this will become a simple Cmp/Bool/CMove set to clone-up.
     Node *bol, *cmov;
     if( !(n->outcnt() == 1 && n->unique_out()->is_Bool() &&
           (bol = n->unique_out()->as_Bool()) &&
           (get_ctrl(bol) == blk1 ||
            get_ctrl(bol) == blk2) &&
           bol->outcnt() == 1 &&
           bol->unique_out()->is_CMove() &&
           (cmov = bol->unique_out()->as_CMove()) &&
           (get_ctrl(cmov) == blk1 ||
            get_ctrl(cmov) == blk2) ) ) {
       // Must clone down
 #ifndef PRODUCT
       if( PrintOpto && VerifyLoopOptimizations ) {
         tty->print("Cloning down: ");
         n->dump();
       }
 #endif
       // Clone down any block-local BoolNode uses of this CmpNode
       for (DUIterator i = n->outs(); n->has_out(i); i++) {
         Node* bol = n->out(i);
         assert( bol->is_Bool(), "" );
         if (bol->outcnt() == 1) {
           Node* use = bol->unique_out();
           Node *use_c = use->is_If() ? use->in(0) : get_ctrl(use);
           if (use_c == blk1 || use_c == blk2) {
             continue;
           }
         }
         if (get_ctrl(bol) == blk1 || get_ctrl(bol) == blk2) {
           // Recursively sink any BoolNode
 #ifndef PRODUCT
           if( PrintOpto && VerifyLoopOptimizations ) {
             tty->print("Cloning down: ");
             bol->dump();
           }
 #endif
           for (DUIterator_Last jmin, j = bol->last_outs(jmin); j >= jmin; --j) {
             // Uses are either IfNodes or CMoves
             Node* iff = bol->last_out(j);
             assert( iff->in(1) == bol, "" );
             // Get control block of either the CMove or the If input
             Node *iff_ctrl = iff->is_If() ? iff->in(0) : get_ctrl(iff);
             Node *x = bol->clone();
             register_new_node(x, iff_ctrl);
             _igvn.hash_delete(iff);
             iff->set_req(1, x);
             _igvn._worklist.push(iff);
           }
           _igvn.remove_dead_node( bol );
           --i;
         }
       }
       // Clone down this CmpNode
       for (DUIterator_Last jmin, j = n->last_outs(jmin); j >= jmin; --j) {
         Node* bol = n->last_out(j);
         assert( bol->in(1) == n, "" );
         Node *x = n->clone();
         register_new_node(x, get_ctrl(bol));
         _igvn.hash_delete(bol);
         bol->set_req(1, x);
         _igvn._worklist.push(bol);
       }
       _igvn.remove_dead_node( n );
       return true;
     }
   }
   // See if splitting-up a Store.  Any anti-dep loads must go up as
   // well.  An anti-dep load might be in the wrong block, because in
   // this particular layout/schedule we ignored anti-deps and allow
   // memory to be alive twice.  This only works if we do the same
   // operations on anti-dep loads as we do their killing stores.
   if( n->is_Store() && n->in(MemNode::Memory)->in(0) == n->in(0) ) {
     // Get store's memory slice
     int alias_idx = C->get_alias_index(_igvn.type(n->in(MemNode::Address))->is_ptr());
     // Get memory-phi anti-dep loads will be using
     Node *memphi = n->in(MemNode::Memory);
     assert( memphi->is_Phi(), "" );
     // Hoist any anti-dep load to the splitting block;
     // it will then "split-up".
     for (DUIterator_Fast imax,i = memphi->fast_outs(imax); i < imax; i++) {
       Node *load = memphi->fast_out(i);
       if( load->is_Load() && alias_idx == C->get_alias_index(_igvn.type(load->in(MemNode::Address))->is_ptr()) )
         set_ctrl(load,blk1);
     }
   }
   // Found some other Node; must clone it up
 #ifndef PRODUCT
   if( PrintOpto && VerifyLoopOptimizations ) {
     tty->print("Cloning up: ");
     n->dump();
   }
 #endif
   // Now actually split-up this guy.  One copy per control path merging.
   Node *phi = PhiNode::make_blank(blk1, n);
   for( uint j = 1; j < blk1->req(); j++ ) {
     Node *x = n->clone();
     if( n->in(0) && n->in(0) == blk1 )
       x->set_req( 0, blk1->in(j) );
     for( uint i = 1; i < n->req(); i++ ) {
       Node *m = n->in(i);
       if( get_ctrl(m) == blk1 ) {
         assert( m->in(0) == blk1, "" );
         x->set_req( i, m->in(j) );
       }
     }
     register_new_node( x, blk1->in(j) );
     phi->init_req( j, x );
   }
   // Announce phi to optimizer
   register_new_node(phi, blk1);
   // Remove cloned-up value from optimizer; use phi instead
   _igvn.hash_delete(n);
   _igvn.subsume_node( n, phi );
   // (There used to be a self-recursive call to split_up() here,
   // but it is not needed.  All necessary forward walking is done
   // by do_split_if() below.)
   return true;
 }
 //------------------------------register_new_node------------------------------
 void PhaseIdealLoop::register_new_node( Node *n, Node *blk ) {
   _igvn.register_new_node_with_optimizer(n);
   set_ctrl(n, blk);
   IdealLoopTree *loop = get_loop(blk);
   if( !loop->_child )
     loop->_body.push(n);
 }
 //------------------------------small_cache------------------------------------
 struct small_cache : public Dict {
   small_cache() : Dict( cmpkey, hashptr ) {}
   Node *probe( Node *use_blk ) { return (Node*)((*this)[use_blk]); }
   void lru_insert( Node *use_blk, Node *new_def ) { Insert(use_blk,new_def); }
 };
 //------------------------------spinup-----------------------------------------
 // "Spin up" the dominator tree, starting at the use site and stopping when we
 // find the post-dominating point.
 // We must be at the merge point which post-dominates 'new_false' and
 // 'new_true'.  Figure out which edges into the RegionNode eventually lead up
 // to false and which to true.  Put in a PhiNode to merge values; plug in
 // the appropriate false-arm or true-arm values.  If some path leads to the
 // original IF, then insert a Phi recursively.
 Node *PhaseIdealLoop::spinup( Node *iff_dom, Node *new_false, Node *new_true, Node *use_blk, Node *def, small_cache *cache ) {
   if (use_blk->is_top())        // Handle dead uses
     return use_blk;
   Node *prior_n = (Node*)0xdeadbeef;
   Node *n = use_blk;            // Get path input
   assert( use_blk != iff_dom, "" );
   // Here's the "spinup" the dominator tree loop.  Do a cache-check
   // along the way, in case we've come this way before.
   while( n != iff_dom ) {       // Found post-dominating point?
     prior_n = n;
     n = idom(n);                // Search higher
     Node *s = cache->probe( prior_n ); // Check cache
     if( s ) return s;           // Cache hit!
   }
   Node *phi_post;
   if( prior_n == new_false || prior_n == new_true ) {
     phi_post = def->clone();
     phi_post->set_req(0, prior_n );
     register_new_node(phi_post, prior_n);
   } else {
     // This method handles both control uses (looking for Regions) or data
     // uses (looking for Phis).  If looking for a control use, then we need
     // to insert a Region instead of a Phi; however Regions always exist
     // previously (the hash_find_insert below would always hit) so we can
     // return the existing Region.
     if( def->is_CFG() ) {
       phi_post = prior_n;       // If looking for CFG, return prior
     } else {
       assert( def->is_Phi(), "" );
       assert( prior_n->is_Region(), "must be a post-dominating merge point" );
       // Need a Phi here
       phi_post = PhiNode::make_blank(prior_n, def);
       // Search for both true and false on all paths till find one.
       for( uint i = 1; i < phi_post->req(); i++ ) // For all paths
         phi_post->init_req( i, spinup( iff_dom, new_false, new_true, prior_n->in(i), def, cache ) );
       Node *t = _igvn.hash_find_insert(phi_post);
       if( t ) {                 // See if we already have this one
         // phi_post will not be used, so kill it
         _igvn.remove_dead_node(phi_post);
         phi_post->destruct();
         phi_post = t;
       } else {
         register_new_node( phi_post, prior_n );
       }
     }
   }
   // Update cache everywhere
   prior_n = (Node*)0xdeadbeef;  // Reset IDOM walk
   n = use_blk;                  // Get path input
   // Spin-up the idom tree again, basically doing path-compression.
   // Insert cache entries along the way, so that if we ever hit this
   // point in the IDOM tree again we'll stop immediately on a cache hit.
   while( n != iff_dom ) {       // Found post-dominating point?
     prior_n = n;
     n = idom(n);                // Search higher
     cache->lru_insert( prior_n, phi_post ); // Fill cache
   } // End of while not gone high enough
   return phi_post;
 }
 //------------------------------find_use_block---------------------------------
 // Find the block a USE is in.  Normally USE's are in the same block as the
 // using instruction.  For Phi-USE's, the USE is in the predecessor block
 // along the corresponding path.
 Node *PhaseIdealLoop::find_use_block( Node *use, Node *def, Node *old_false, Node *new_false, Node *old_true, Node *new_true ) {
   // CFG uses are their own block
   if( use->is_CFG() )
     return use;
   if( use->is_Phi() ) {         // Phi uses in prior block
     // Grab the first Phi use; there may be many.
     // Each will be handled as a separate iteration of
     // the "while( phi->outcnt() )" loop.
     uint j;
     for( j = 1; j < use->req(); j++ )
       if( use->in(j) == def )
         break;
     assert( j < use->req(), "def should be among use's inputs" );
     return use->in(0)->in(j);
   }
   // Normal (non-phi) use
   Node *use_blk = get_ctrl(use);
   // Some uses are directly attached to the old (and going away)
   // false and true branches.
   if( use_blk == old_false ) {
     use_blk = new_false;
     set_ctrl(use, new_false);
   }
   if( use_blk == old_true ) {
     use_blk = new_true;
     set_ctrl(use, new_true);
   }
   if (use_blk == NULL) {        // He's dead, Jim
     _igvn.hash_delete(use);
     _igvn.subsume_node(use, C->top());
   }
   return use_blk;
 }
 //------------------------------handle_use-------------------------------------
 // Handle uses of the merge point.  Basically, split-if makes the merge point
 // go away so all uses of the merge point must go away as well.  Most block
 // local uses have already been split-up, through the merge point.  Uses from
 // far below the merge point can't always be split up (e.g., phi-uses are
 // pinned) and it makes too much stuff live.  Instead we use a path-based
 // solution to move uses down.
 //
 // If the use is along the pre-split-CFG true branch, then the new use will
 // be from the post-split-CFG true merge point.  Vice-versa for the false
 // path.  Some uses will be along both paths; then we sink the use to the
 // post-dominating location; we may need to insert a Phi there.
 void PhaseIdealLoop::handle_use( Node *use, Node *def, small_cache *cache, Node *region_dom, Node *new_false, Node *new_true, Node *old_false, Node *old_true ) {
   Node *use_blk = find_use_block(use,def,old_false,new_false,old_true,new_true);
   if( !use_blk ) return;        // He's dead, Jim
   // Walk up the dominator tree until I hit either the old IfFalse, the old
   // IfTrue or the old If.  Insert Phis where needed.
   Node *new_def = spinup( region_dom, new_false, new_true, use_blk, def, cache );
   // Found where this USE goes.  Re-point him.
   uint i;
   for( i = 0; i < use->req(); i++ )
     if( use->in(i) == def )
       break;
   assert( i < use->req(), "def should be among use's inputs" );
   _igvn.hash_delete(use);
   use->set_req(i, new_def);
   _igvn._worklist.push(use);
 }
 //------------------------------do_split_if------------------------------------
 // Found an If getting its condition-code input from a Phi in the same block.
 // Split thru the Region.
 void PhaseIdealLoop::do_split_if( Node *iff ) {
 #ifndef PRODUCT
   if( PrintOpto && VerifyLoopOptimizations )
     tty->print_cr("Split-if");
 #endif
   C->set_major_progress();
   Node *region = iff->in(0);
   Node *region_dom = idom(region);
   // We are going to clone this test (and the control flow with it) up through
   // the incoming merge point.  We need to empty the current basic block.
   // Clone any instructions which must be in this block up through the merge
   // point.
   DUIterator i, j;
   bool progress = true;
   while (progress) {
     progress = false;
     for (i = region->outs(); region->has_out(i); i++) {
       Node* n = region->out(i);
       if( n == region ) continue;
       // The IF to be split is OK.
       if( n == iff ) continue;
       if( !n->is_Phi() ) {      // Found pinned memory op or such
         if (split_up(n, region, iff)) {
           i = region->refresh_out_pos(i);
           progress = true;
         }
         continue;
       }
       assert( n->in(0) == region, "" );
       // Recursively split up all users of a Phi
       for (j = n->outs(); n->has_out(j); j++) {
         Node* m = n->out(j);
         // If m is dead, throw it away, and declare progress
         if (_nodes[m->_idx] == NULL) {
           _igvn.remove_dead_node(m);
           // fall through
         }
         else if (m != iff && split_up(m, region, iff)) {
           // fall through
         } else {
           continue;
         }
         // Something unpredictable changed.
         // Tell the iterators to refresh themselves, and rerun the loop.
         i = region->refresh_out_pos(i);
         j = region->refresh_out_pos(j);
         progress = true;
       }
     }
   }
   // Now we have no instructions in the block containing the IF.
   // Split the IF.
   Node *new_iff = split_thru_region( iff, region );
   // Replace both uses of 'new_iff' with Regions merging True/False
   // paths.  This makes 'new_iff' go dead.
   Node *old_false, *old_true;
   Node *new_false, *new_true;
   for (DUIterator_Last j2min, j2 = iff->last_outs(j2min); j2 >= j2min; --j2) {
     Node *ifp = iff->last_out(j2);
     assert( ifp->Opcode() == Op_IfFalse || ifp->Opcode() == Op_IfTrue, "" );
     ifp->set_req(0, new_iff);
     Node *ifpx = split_thru_region( ifp, region );
     // Replace 'If' projection of a Region with a Region of
     // 'If' projections.
     ifpx->set_req(0, ifpx);       // A TRUE RegionNode
     // Setup dominator info
     set_idom(ifpx, region_dom, dom_depth(region_dom) + 1);
     // Check for splitting loop tails
     if( get_loop(iff)->tail() == ifp )
       get_loop(iff)->_tail = ifpx;
     // Replace in the graph with lazy-update mechanism
     new_iff->set_req(0, new_iff); // hook self so it does not go dead
     lazy_replace_proj( ifp, ifpx );
     new_iff->set_req(0, region);
     // Record bits for later xforms
     if( ifp->Opcode() == Op_IfFalse ) {
       old_false = ifp;
       new_false = ifpx;
     } else {
       old_true = ifp;
       new_true = ifpx;
     }
   }
   _igvn.remove_dead_node(new_iff);
   // Lazy replace IDOM info with the region's dominator
   lazy_replace( iff, region_dom );
   // Now make the original merge point go dead, by handling all its uses.
   small_cache region_cache;
   // Preload some control flow in region-cache
   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
       _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() ) {
       // Need a per-def cache.  Phi represents a def, so make a cache
       small_cache phi_cache;
       // Inspect all Phi uses to make the Phi go dead
       for (DUIterator_Last lmin, l = phi->last_outs(lmin); l >= lmin; --l) {
         Node* use = phi->last_out(l);
         // Compute the new DEF for this USE.  New DEF depends on the path
         // taken from the original DEF to the USE.  The new DEF may be some
         // 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 );
       } // 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 {
       // 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 );
     }
   } // End of while merge point has phis
   // 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.
   lazy_replace( region, region_dom );
 #ifndef PRODUCT
   if( VerifyLoopOptimizations ) verify();
 #endif
 }

Mercurial > jdk8-mips64-public > hotspot / annotate

src/share/vm/opto/split_if.cpp@98cb887364d3 (annotated)

src/share/vm/opto/split_if.cpp