Mercurial > jdk8-mips64-public > hotspot / file revision

 /*

  * 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

 }