jdk8-mips64-public/hotspot: src/share/vm/opto/ifnode.cpp@09d0d56ca735 (annotated)

src/share/vm/opto/ifnode.cpp@09d0d56ca735 (annotated)

src/share/vm/opto/ifnode.cpp

Thu, 01 Jun 2017 23:19:47 -0700

author: rraghavan
date: Thu, 01 Jun 2017 23:19:47 -0700
changeset 8777: 09d0d56ca735
parent 7421: e3d0aaab84aa
child 8856: ac27a9c85bea
child 8907: 9f401c01775b
permissions: -rw-r--r--

8175345: Reported null pointer dereference defect groups
Summary: Added required explicit NULL checks
Reviewed-by: thartmann, kvn

 /*
  * Copyright (c) 2000, 2013, Oracle and/or its affiliates. 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  * or visit www.oracle.com if you need additional information or have any
  * questions.
  *
  */
 #include "precompiled.hpp"
 #include "memory/allocation.inline.hpp"
 #include "opto/addnode.hpp"
 #include "opto/cfgnode.hpp"
 #include "opto/connode.hpp"
 #include "opto/loopnode.hpp"
 #include "opto/phaseX.hpp"
 #include "opto/runtime.hpp"
 #include "opto/subnode.hpp"
 // Portions of code courtesy of Clifford Click
 // Optimization - Graph Style
 extern int explicit_null_checks_elided;
 //=============================================================================
 //------------------------------Value------------------------------------------
 // Return a tuple for whichever arm of the IF is reachable
 const Type *IfNode::Value( PhaseTransform *phase ) const {
   if( !in(0) ) return Type::TOP;
   if( phase->type(in(0)) == Type::TOP )
     return Type::TOP;
   const Type *t = phase->type(in(1));
   if( t == Type::TOP )          // data is undefined
     return TypeTuple::IFNEITHER; // unreachable altogether
   if( t == TypeInt::ZERO )      // zero, or false
     return TypeTuple::IFFALSE;  // only false branch is reachable
   if( t == TypeInt::ONE )       // 1, or true
     return TypeTuple::IFTRUE;   // only true branch is reachable
   assert( t == TypeInt::BOOL, "expected boolean type" );
   return TypeTuple::IFBOTH;     // No progress
 }
 const RegMask &IfNode::out_RegMask() const {
   return RegMask::Empty;
 }
 //------------------------------split_if---------------------------------------
 // Look for places where we merge constants, then test on the merged value.
 // If the IF test will be constant folded on the path with the constant, we
 // win by splitting the IF to before the merge point.
 static Node* split_if(IfNode *iff, PhaseIterGVN *igvn) {
   // I could be a lot more general here, but I'm trying to squeeze this
   // in before the Christmas '98 break so I'm gonna be kinda restrictive
   // on the patterns I accept.  CNC
   // Look for a compare of a constant and a merged value
   Node *i1 = iff->in(1);
   if( !i1->is_Bool() ) return NULL;
   BoolNode *b = i1->as_Bool();
   Node *cmp = b->in(1);
   if( !cmp->is_Cmp() ) return NULL;
   i1 = cmp->in(1);
   if( i1 == NULL || !i1->is_Phi() ) return NULL;
   PhiNode *phi = i1->as_Phi();
   if( phi->is_copy() ) return NULL;
   Node *con2 = cmp->in(2);
   if( !con2->is_Con() ) return NULL;
   // See that the merge point contains some constants
   Node *con1=NULL;
   uint i4;
   for( i4 = 1; i4 < phi->req(); i4++ ) {
     con1 = phi->in(i4);
     if( !con1 ) return NULL;    // Do not optimize partially collapsed merges
     if( con1->is_Con() ) break; // Found a constant
     // Also allow null-vs-not-null checks
     const TypePtr *tp = igvn->type(con1)->isa_ptr();
     if( tp && tp->_ptr == TypePtr::NotNull )
       break;
   }
   if( i4 >= phi->req() ) return NULL; // Found no constants
   igvn->C->set_has_split_ifs(true); // Has chance for split-if
   // Make sure that the compare can be constant folded away
   Node *cmp2 = cmp->clone();
   cmp2->set_req(1,con1);
   cmp2->set_req(2,con2);
   const Type *t = cmp2->Value(igvn);
   // This compare is dead, so whack it!
   igvn->remove_dead_node(cmp2);
   if( !t->singleton() ) return NULL;
   // No intervening control, like a simple Call
   Node *r = iff->in(0);
   if( !r->is_Region() ) return NULL;
   if( phi->region() != r ) return NULL;
   // No other users of the cmp/bool
   if (b->outcnt() != 1 || cmp->outcnt() != 1) {
     //tty->print_cr("many users of cmp/bool");
     return NULL;
   }
   // Make sure we can determine where all the uses of merged values go
   for (DUIterator_Fast jmax, j = r->fast_outs(jmax); j < jmax; j++) {
     Node* u = r->fast_out(j);
     if( u == r ) continue;
     if( u == iff ) continue;
     if( u->outcnt() == 0 ) continue; // use is dead & ignorable
     if( !u->is_Phi() ) {
       /*
       if( u->is_Start() ) {
         tty->print_cr("Region has inlined start use");
       } else {
         tty->print_cr("Region has odd use");
         u->dump(2);
       }*/
       return NULL;
     }
     if( u != phi ) {
       // CNC - do not allow any other merged value
       //tty->print_cr("Merging another value");
       //u->dump(2);
       return NULL;
     }
     // Make sure we can account for all Phi uses
     for (DUIterator_Fast kmax, k = u->fast_outs(kmax); k < kmax; k++) {
       Node* v = u->fast_out(k); // User of the phi
       // CNC - Allow only really simple patterns.
       // In particular I disallow AddP of the Phi, a fairly common pattern
       if( v == cmp ) continue;  // The compare is OK
       if( (v->is_ConstraintCast()) &&
           v->in(0)->in(0) == iff )
         continue;               // CastPP/II of the IfNode is OK
       // Disabled following code because I cannot tell if exactly one
       // path dominates without a real dominator check. CNC 9/9/1999
       //uint vop = v->Opcode();
       //if( vop == Op_Phi ) {     // Phi from another merge point might be OK
       //  Node *r = v->in(0);     // Get controlling point
       //  if( !r ) return NULL;   // Degraded to a copy
       //  // Find exactly one path in (either True or False doms, but not IFF)
       //  int cnt = 0;
       //  for( uint i = 1; i < r->req(); i++ )
       //    if( r->in(i) && r->in(i)->in(0) == iff )
       //      cnt++;
       //  if( cnt == 1 ) continue; // Exactly one of True or False guards Phi
       //}
       if( !v->is_Call() ) {
         /*
         if( v->Opcode() == Op_AddP ) {
           tty->print_cr("Phi has AddP use");
         } else if( v->Opcode() == Op_CastPP ) {
           tty->print_cr("Phi has CastPP use");
         } else if( v->Opcode() == Op_CastII ) {
           tty->print_cr("Phi has CastII use");
         } else {
           tty->print_cr("Phi has use I cant be bothered with");
         }
         */
       }
       return NULL;
       /* CNC - Cut out all the fancy acceptance tests
       // Can we clone this use when doing the transformation?
       // If all uses are from Phis at this merge or constants, then YES.
       if( !v->in(0) && v != cmp ) {
         tty->print_cr("Phi has free-floating use");
         v->dump(2);
         return NULL;
       }
       for( uint l = 1; l < v->req(); l++ ) {
         if( (!v->in(l)->is_Phi() || v->in(l)->in(0) != r) &&
             !v->in(l)->is_Con() ) {
           tty->print_cr("Phi has use");
           v->dump(2);
           return NULL;
         } // End of if Phi-use input is neither Phi nor Constant
       } // End of for all inputs to Phi-use
       */
     } // End of for all uses of Phi
   } // End of for all uses of Region
   // Only do this if the IF node is in a sane state
   if (iff->outcnt() != 2)
     return NULL;
   // Got a hit!  Do the Mondo Hack!
   //
   //ABC  a1c   def   ghi            B     1     e     h   A C   a c   d f   g i
   // R - Phi - Phi - Phi            Rc - Phi - Phi - Phi   Rx - Phi - Phi - Phi
   //     cmp - 2                         cmp - 2               cmp - 2
   //       bool                            bool_c                bool_x
   //       if                               if_c                  if_x
   //      T  F                              T  F                  T  F
   // ..s..    ..t ..                   ..s..    ..t..        ..s..    ..t..
   //
   // Split the paths coming into the merge point into 2 separate groups of
   // merges.  On the left will be all the paths feeding constants into the
   // Cmp's Phi.  On the right will be the remaining paths.  The Cmp's Phi
   // will fold up into a constant; this will let the Cmp fold up as well as
   // all the control flow.  Below the original IF we have 2 control
   // dependent regions, 's' and 't'.  Now we will merge the two paths
   // just prior to 's' and 't' from the two IFs.  At least 1 path (and quite
   // likely 2 or more) will promptly constant fold away.
   PhaseGVN *phase = igvn;
   // Make a region merging constants and a region merging the rest
   uint req_c = 0;
   Node* predicate_proj = NULL;
   for (uint ii = 1; ii < r->req(); ii++) {
     if (phi->in(ii) == con1) {
       req_c++;
     }
     Node* proj = PhaseIdealLoop::find_predicate(r->in(ii));
     if (proj != NULL) {
       assert(predicate_proj == NULL, "only one predicate entry expected");
       predicate_proj = proj;
     }
   }
   Node* predicate_c = NULL;
   Node* predicate_x = NULL;
   bool counted_loop = r->is_CountedLoop();
   Node *region_c = new (igvn->C) RegionNode(req_c + 1);
   Node *phi_c    = con1;
   uint  len      = r->req();
   Node *region_x = new (igvn->C) RegionNode(len - req_c);
   Node *phi_x    = PhiNode::make_blank(region_x, phi);
   for (uint i = 1, i_c = 1, i_x = 1; i < len; i++) {
     if (phi->in(i) == con1) {
       region_c->init_req( i_c++, r  ->in(i) );
       if (r->in(i) == predicate_proj)
         predicate_c = predicate_proj;
     } else {
       region_x->init_req( i_x,   r  ->in(i) );
       phi_x   ->init_req( i_x++, phi->in(i) );
       if (r->in(i) == predicate_proj)
         predicate_x = predicate_proj;
     }
   }
   if (predicate_c != NULL && (req_c > 1)) {
     assert(predicate_x == NULL, "only one predicate entry expected");
     predicate_c = NULL; // Do not clone predicate below merge point
   }
   if (predicate_x != NULL && ((len - req_c) > 2)) {
     assert(predicate_c == NULL, "only one predicate entry expected");
     predicate_x = NULL; // Do not clone predicate below merge point
   }
   // Register the new RegionNodes but do not transform them.  Cannot
   // transform until the entire Region/Phi conglomerate has been hacked
   // as a single huge transform.
   igvn->register_new_node_with_optimizer( region_c );
   igvn->register_new_node_with_optimizer( region_x );
   // Prevent the untimely death of phi_x.  Currently he has no uses.  He is
   // about to get one.  If this only use goes away, then phi_x will look dead.
   // However, he will be picking up some more uses down below.
   Node *hook = new (igvn->C) Node(4);
   hook->init_req(0, phi_x);
   hook->init_req(1, phi_c);
   phi_x = phase->transform( phi_x );
   // Make the compare
   Node *cmp_c = phase->makecon(t);
   Node *cmp_x = cmp->clone();
   cmp_x->set_req(1,phi_x);
   cmp_x->set_req(2,con2);
   cmp_x = phase->transform(cmp_x);
   // Make the bool
   Node *b_c = phase->transform(new (igvn->C) BoolNode(cmp_c,b->_test._test));
   Node *b_x = phase->transform(new (igvn->C) BoolNode(cmp_x,b->_test._test));
   // Make the IfNode
   IfNode *iff_c = new (igvn->C) IfNode(region_c,b_c,iff->_prob,iff->_fcnt);
   igvn->set_type_bottom(iff_c);
   igvn->_worklist.push(iff_c);
   hook->init_req(2, iff_c);
   IfNode *iff_x = new (igvn->C) IfNode(region_x,b_x,iff->_prob, iff->_fcnt);
   igvn->set_type_bottom(iff_x);
   igvn->_worklist.push(iff_x);
   hook->init_req(3, iff_x);
   // Make the true/false arms
   Node *iff_c_t = phase->transform(new (igvn->C) IfTrueNode (iff_c));
   Node *iff_c_f = phase->transform(new (igvn->C) IfFalseNode(iff_c));
   if (predicate_c != NULL) {
     assert(predicate_x == NULL, "only one predicate entry expected");
     // Clone loop predicates to each path
     iff_c_t = igvn->clone_loop_predicates(predicate_c, iff_c_t, !counted_loop);
     iff_c_f = igvn->clone_loop_predicates(predicate_c, iff_c_f, !counted_loop);
   }
   Node *iff_x_t = phase->transform(new (igvn->C) IfTrueNode (iff_x));
   Node *iff_x_f = phase->transform(new (igvn->C) IfFalseNode(iff_x));
   if (predicate_x != NULL) {
     assert(predicate_c == NULL, "only one predicate entry expected");
     // Clone loop predicates to each path
     iff_x_t = igvn->clone_loop_predicates(predicate_x, iff_x_t, !counted_loop);
     iff_x_f = igvn->clone_loop_predicates(predicate_x, iff_x_f, !counted_loop);
   }
   // Merge the TRUE paths
   Node *region_s = new (igvn->C) RegionNode(3);
   igvn->_worklist.push(region_s);
   region_s->init_req(1, iff_c_t);
   region_s->init_req(2, iff_x_t);
   igvn->register_new_node_with_optimizer( region_s );
   // Merge the FALSE paths
   Node *region_f = new (igvn->C) RegionNode(3);
   igvn->_worklist.push(region_f);
   region_f->init_req(1, iff_c_f);
   region_f->init_req(2, iff_x_f);
   igvn->register_new_node_with_optimizer( region_f );
   igvn->hash_delete(cmp);// Remove soon-to-be-dead node from hash table.
   cmp->set_req(1,NULL);  // Whack the inputs to cmp because it will be dead
   cmp->set_req(2,NULL);
   // Check for all uses of the Phi and give them a new home.
   // The 'cmp' got cloned, but CastPP/IIs need to be moved.
   Node *phi_s = NULL;     // do not construct unless needed
   Node *phi_f = NULL;     // do not construct unless needed
   for (DUIterator_Last i2min, i2 = phi->last_outs(i2min); i2 >= i2min; --i2) {
     Node* v = phi->last_out(i2);// User of the phi
     igvn->rehash_node_delayed(v); // Have to fixup other Phi users
     uint vop = v->Opcode();
     Node *proj = NULL;
     if( vop == Op_Phi ) {       // Remote merge point
       Node *r = v->in(0);
       for (uint i3 = 1; i3 < r->req(); i3++)
         if (r->in(i3) && r->in(i3)->in(0) == iff) {
           proj = r->in(i3);
           break;
         }
     } else if( v->is_ConstraintCast() ) {
       proj = v->in(0);          // Controlling projection
     } else {
       assert( 0, "do not know how to handle this guy" );
     }
     Node *proj_path_data, *proj_path_ctrl;
     if( proj->Opcode() == Op_IfTrue ) {
       if( phi_s == NULL ) {
         // Only construct phi_s if needed, otherwise provides
         // interfering use.
         phi_s = PhiNode::make_blank(region_s,phi);
         phi_s->init_req( 1, phi_c );
         phi_s->init_req( 2, phi_x );
         hook->add_req(phi_s);
         phi_s = phase->transform(phi_s);
       }
       proj_path_data = phi_s;
       proj_path_ctrl = region_s;
     } else {
       if( phi_f == NULL ) {
         // Only construct phi_f if needed, otherwise provides
         // interfering use.
         phi_f = PhiNode::make_blank(region_f,phi);
         phi_f->init_req( 1, phi_c );
         phi_f->init_req( 2, phi_x );
         hook->add_req(phi_f);
         phi_f = phase->transform(phi_f);
       }
       proj_path_data = phi_f;
       proj_path_ctrl = region_f;
     }
     // Fixup 'v' for for the split
     if( vop == Op_Phi ) {       // Remote merge point
       uint i;
       for( i = 1; i < v->req(); i++ )
         if( v->in(i) == phi )
           break;
       v->set_req(i, proj_path_data );
     } else if( v->is_ConstraintCast() ) {
       v->set_req(0, proj_path_ctrl );
       v->set_req(1, proj_path_data );
     } else
       ShouldNotReachHere();
   }
   // Now replace the original iff's True/False with region_s/region_t.
   // This makes the original iff go dead.
   for (DUIterator_Last i3min, i3 = iff->last_outs(i3min); i3 >= i3min; --i3) {
     Node* p = iff->last_out(i3);
     assert( p->Opcode() == Op_IfTrue || p->Opcode() == Op_IfFalse, "" );
     Node *u = (p->Opcode() == Op_IfTrue) ? region_s : region_f;
     // Replace p with u
     igvn->add_users_to_worklist(p);
     for (DUIterator_Last lmin, l = p->last_outs(lmin); l >= lmin;) {
       Node* x = p->last_out(l);
       igvn->hash_delete(x);
       uint uses_found = 0;
       for( uint j = 0; j < x->req(); j++ ) {
         if( x->in(j) == p ) {
           x->set_req(j, u);
           uses_found++;
         }
       }
       l -= uses_found;    // we deleted 1 or more copies of this edge
     }
     igvn->remove_dead_node(p);
   }
   // Force the original merge dead
   igvn->hash_delete(r);
   // First, remove region's dead users.
   for (DUIterator_Last lmin, l = r->last_outs(lmin); l >= lmin;) {
     Node* u = r->last_out(l);
     if( u == r ) {
       r->set_req(0, NULL);
     } else {
       assert(u->outcnt() == 0, "only dead users");
       igvn->remove_dead_node(u);
     }
     l -= 1;
   }
   igvn->remove_dead_node(r);
   // Now remove the bogus extra edges used to keep things alive
   igvn->remove_dead_node( hook );
   // Must return either the original node (now dead) or a new node
   // (Do not return a top here, since that would break the uniqueness of top.)
   return new (igvn->C) ConINode(TypeInt::ZERO);
 }
 //------------------------------is_range_check---------------------------------
 // Return 0 if not a range check.  Return 1 if a range check and set index and
 // offset.  Return 2 if we had to negate the test.  Index is NULL if the check
 // is versus a constant.
 int IfNode::is_range_check(Node* &range, Node* &index, jint &offset) {
   Node* b = in(1);
   if (b == NULL || !b->is_Bool())  return 0;
   BoolNode* bn = b->as_Bool();
   Node* cmp = bn->in(1);
   if (cmp == NULL)  return 0;
   if (cmp->Opcode() != Op_CmpU)  return 0;
   Node* l = cmp->in(1);
   Node* r = cmp->in(2);
   int flip_test = 1;
   if (bn->_test._test == BoolTest::le) {
     l = cmp->in(2);
     r = cmp->in(1);
     flip_test = 2;
   } else if (bn->_test._test != BoolTest::lt) {
     return 0;
   }
   if (l->is_top())  return 0;   // Top input means dead test
   if (r->Opcode() != Op_LoadRange)  return 0;
   // We have recognized one of these forms:
   //  Flip 1:  If (Bool[<] CmpU(l, LoadRange)) ...
   //  Flip 2:  If (Bool[<=] CmpU(LoadRange, l)) ...
   // Make sure it's a real range check by requiring an uncommon trap
   // along the OOB path.  Otherwise, it's possible that the user wrote
   // something which optimized to look like a range check but behaves
   // in some other way.
   Node* iftrap = proj_out(flip_test == 2 ? true : false);
   bool found_trap = false;
   if (iftrap != NULL) {
     Node* u = iftrap->unique_ctrl_out();
     if (u != NULL) {
       // It could be a merge point (Region) for uncommon trap.
       if (u->is_Region()) {
         Node* c = u->unique_ctrl_out();
         if (c != NULL) {
           iftrap = u;
           u = c;
         }
       }
       if (u->in(0) == iftrap && u->is_CallStaticJava()) {
         int req = u->as_CallStaticJava()->uncommon_trap_request();
         if (Deoptimization::trap_request_reason(req) ==
             Deoptimization::Reason_range_check) {
           found_trap = true;
         }
       }
     }
   }
   if (!found_trap)  return 0;   // sorry, no cigar
   // Look for index+offset form
   Node* ind = l;
   jint  off = 0;
   if (l->is_top()) {
     return 0;
   } else if (l->Opcode() == Op_AddI) {
     if ((off = l->in(1)->find_int_con(0)) != 0) {
       ind = l->in(2);
     } else if ((off = l->in(2)->find_int_con(0)) != 0) {
       ind = l->in(1);
     }
   } else if ((off = l->find_int_con(-1)) >= 0) {
     // constant offset with no variable index
     ind = NULL;
   } else {
     // variable index with no constant offset (or dead negative index)
     off = 0;
   }
   // Return all the values:
   index  = ind;
   offset = off;
   range  = r;
   return flip_test;
 }
 //------------------------------adjust_check-----------------------------------
 // Adjust (widen) a prior range check
 static void adjust_check(Node* proj, Node* range, Node* index,
                          int flip, jint off_lo, PhaseIterGVN* igvn) {
   PhaseGVN *gvn = igvn;
   // Break apart the old check
   Node *iff = proj->in(0);
   Node *bol = iff->in(1);
   if( bol->is_top() ) return;   // In case a partially dead range check appears
   // bail (or bomb[ASSERT/DEBUG]) if NOT projection-->IfNode-->BoolNode
   DEBUG_ONLY( if( !bol->is_Bool() ) { proj->dump(3); fatal("Expect projection-->IfNode-->BoolNode"); } )
   if( !bol->is_Bool() ) return;
   Node *cmp = bol->in(1);
   // Compute a new check
   Node *new_add = gvn->intcon(off_lo);
   if( index ) {
     new_add = off_lo ? gvn->transform(new (gvn->C) AddINode( index, new_add )) : index;
   }
   Node *new_cmp = (flip == 1)
     ? new (gvn->C) CmpUNode( new_add, range )
     : new (gvn->C) CmpUNode( range, new_add );
   new_cmp = gvn->transform(new_cmp);
   // See if no need to adjust the existing check
   if( new_cmp == cmp ) return;
   // Else, adjust existing check
   Node *new_bol = gvn->transform( new (gvn->C) BoolNode( new_cmp, bol->as_Bool()->_test._test ) );
   igvn->rehash_node_delayed( iff );
   iff->set_req_X( 1, new_bol, igvn );
 }
 //------------------------------up_one_dom-------------------------------------
 // Walk up the dominator tree one step.  Return NULL at root or true
 // complex merges.  Skips through small diamonds.
 Node* IfNode::up_one_dom(Node *curr, bool linear_only) {
   Node *dom = curr->in(0);
   if( !dom )                    // Found a Region degraded to a copy?
     return curr->nonnull_req(); // Skip thru it
   if( curr != dom )             // Normal walk up one step?
     return dom;
   // Use linear_only if we are still parsing, since we cannot
   // trust the regions to be fully filled in.
   if (linear_only)
     return NULL;
   if( dom->is_Root() )
     return NULL;
   // Else hit a Region.  Check for a loop header
   if( dom->is_Loop() )
     return dom->in(1);          // Skip up thru loops
   // Check for small diamonds
   Node *din1, *din2, *din3, *din4;
   if( dom->req() == 3 &&        // 2-path merge point
       (din1 = dom ->in(1)) &&   // Left  path exists
       (din2 = dom ->in(2)) &&   // Right path exists
       (din3 = din1->in(0)) &&   // Left  path up one
       (din4 = din2->in(0)) ) {  // Right path up one
     if( din3->is_Call() &&      // Handle a slow-path call on either arm
         (din3 = din3->in(0)) )
       din3 = din3->in(0);
     if( din4->is_Call() &&      // Handle a slow-path call on either arm
         (din4 = din4->in(0)) )
       din4 = din4->in(0);
     if( din3 == din4 && din3->is_If() )
       return din3;              // Skip around diamonds
   }
   // Give up the search at true merges
   return NULL;                  // Dead loop?  Or hit root?
 }
 //------------------------------filtered_int_type--------------------------------
 // Return a possibly more restrictive type for val based on condition control flow for an if
 const TypeInt* IfNode::filtered_int_type(PhaseGVN* gvn, Node *val, Node* if_proj) {
   assert(if_proj &&
          (if_proj->Opcode() == Op_IfTrue || if_proj->Opcode() == Op_IfFalse), "expecting an if projection");
   if (if_proj->in(0) && if_proj->in(0)->is_If()) {
     IfNode* iff = if_proj->in(0)->as_If();
     if (iff->in(1) && iff->in(1)->is_Bool()) {
       BoolNode* bol = iff->in(1)->as_Bool();
       if (bol->in(1) && bol->in(1)->is_Cmp()) {
         const CmpNode* cmp  = bol->in(1)->as_Cmp();
         if (cmp->in(1) == val) {
           const TypeInt* cmp2_t = gvn->type(cmp->in(2))->isa_int();
           if (cmp2_t != NULL) {
             jint lo = cmp2_t->_lo;
             jint hi = cmp2_t->_hi;
             BoolTest::mask msk = if_proj->Opcode() == Op_IfTrue ? bol->_test._test : bol->_test.negate();
             switch (msk) {
             case BoolTest::ne:
               // Can't refine type
               return NULL;
             case BoolTest::eq:
               return cmp2_t;
             case BoolTest::lt:
               lo = TypeInt::INT->_lo;
               if (hi - 1 < hi) {
                 hi = hi - 1;
               }
               break;
             case BoolTest::le:
               lo = TypeInt::INT->_lo;
               break;
             case BoolTest::gt:
               if (lo + 1 > lo) {
                 lo = lo + 1;
               }
               hi = TypeInt::INT->_hi;
               break;
             case BoolTest::ge:
               // lo unchanged
               hi = TypeInt::INT->_hi;
               break;
             }
             const TypeInt* rtn_t = TypeInt::make(lo, hi, cmp2_t->_widen);
             return rtn_t;
           }
         }
       }
     }
   }
   return NULL;
 }
 //------------------------------fold_compares----------------------------
 // See if a pair of CmpIs can be converted into a CmpU.  In some cases
 // the direction of this if is determined by the preceding if so it
 // can be eliminate entirely.  Given an if testing (CmpI n c) check
 // for an immediately control dependent if that is testing (CmpI n c2)
 // and has one projection leading to this if and the other projection
 // leading to a region that merges one of this ifs control
 // projections.
 //
 //                   If
 //                  / |
 //                 /  |
 //                /   |
 //              If    |
 //              /\    |
 //             /  \   |
 //            /    \  |
 //           /    Region
 //
 Node* IfNode::fold_compares(PhaseGVN* phase) {
   if (Opcode() != Op_If) return NULL;
   Node* this_cmp = in(1)->in(1);
   if (this_cmp != NULL && this_cmp->Opcode() == Op_CmpI &&
       this_cmp->in(2)->is_Con() && this_cmp->in(2) != phase->C->top()) {
     Node* ctrl = in(0);
     BoolNode* this_bool = in(1)->as_Bool();
     Node* n = this_cmp->in(1);
     int hi = this_cmp->in(2)->get_int();
     if (ctrl != NULL && ctrl->is_Proj() && ctrl->outcnt() == 1 &&
         ctrl->in(0)->is_If() &&
         ctrl->in(0)->outcnt() == 2 &&
         ctrl->in(0)->in(1)->is_Bool() &&
         ctrl->in(0)->in(1)->in(1)->Opcode() == Op_CmpI &&
         ctrl->in(0)->in(1)->in(1)->in(2)->is_Con() &&
         ctrl->in(0)->in(1)->in(1)->in(2) != phase->C->top() &&
         ctrl->in(0)->in(1)->in(1)->in(1) == n) {
       IfNode* dom_iff = ctrl->in(0)->as_If();
       Node* otherproj = dom_iff->proj_out(!ctrl->as_Proj()->_con);
       if (otherproj->outcnt() == 1 && otherproj->unique_out()->is_Region() &&
           this_bool->_test._test != BoolTest::ne && this_bool->_test._test != BoolTest::eq) {
         // Identify which proj goes to the region and which continues on
         RegionNode* region = otherproj->unique_out()->as_Region();
         Node* success = NULL;
         Node* fail = NULL;
         for (int i = 0; i < 2; i++) {
           Node* proj = proj_out(i);
           if (success == NULL && proj->outcnt() == 1 && proj->unique_out() == region) {
             success = proj;
           } else if (fail == NULL) {
             fail = proj;
           } else {
             success = fail = NULL;
           }
         }
         if (success != NULL && fail != NULL && !region->has_phi()) {
           int lo = dom_iff->in(1)->in(1)->in(2)->get_int();
           BoolNode* dom_bool = dom_iff->in(1)->as_Bool();
           Node* dom_cmp =  dom_bool->in(1);
           const TypeInt* failtype  = filtered_int_type(phase, n, ctrl);
           if (failtype != NULL) {
             const TypeInt* type2 = filtered_int_type(phase, n, fail);
             if (type2 != NULL) {
               failtype = failtype->join(type2)->is_int();
             } else {
               failtype = NULL;
             }
           }
           if (failtype != NULL &&
               dom_bool->_test._test != BoolTest::ne && dom_bool->_test._test != BoolTest::eq) {
             int bound = failtype->_hi - failtype->_lo + 1;
             if (failtype->_hi != max_jint && failtype->_lo != min_jint && bound > 1) {
               // Merge the two compares into a single unsigned compare by building  (CmpU (n - lo) hi)
               BoolTest::mask cond = fail->as_Proj()->_con ? BoolTest::lt : BoolTest::ge;
               Node* adjusted = phase->transform(new (phase->C) SubINode(n, phase->intcon(failtype->_lo)));
               Node* newcmp = phase->transform(new (phase->C) CmpUNode(adjusted, phase->intcon(bound)));
               Node* newbool = phase->transform(new (phase->C) BoolNode(newcmp, cond));
               phase->is_IterGVN()->replace_input_of(dom_iff, 1, phase->intcon(ctrl->as_Proj()->_con));
               phase->hash_delete(this);
               set_req(1, newbool);
               return this;
             }
             if (failtype->_lo > failtype->_hi) {
               // previous if determines the result of this if so
               // replace Bool with constant
               phase->hash_delete(this);
               set_req(1, phase->intcon(success->as_Proj()->_con));
               return this;
             }
           }
         }
       }
     }
   }
   return NULL;
 }
 //------------------------------remove_useless_bool----------------------------
 // Check for people making a useless boolean: things like
 // if( (x < y ? true : false) ) { ... }
 // Replace with if( x < y ) { ... }
 static Node *remove_useless_bool(IfNode *iff, PhaseGVN *phase) {
   Node *i1 = iff->in(1);
   if( !i1->is_Bool() ) return NULL;
   BoolNode *bol = i1->as_Bool();
   Node *cmp = bol->in(1);
   if( cmp->Opcode() != Op_CmpI ) return NULL;
   // Must be comparing against a bool
   const Type *cmp2_t = phase->type( cmp->in(2) );
   if( cmp2_t != TypeInt::ZERO &&
       cmp2_t != TypeInt::ONE )
     return NULL;
   // Find a prior merge point merging the boolean
   i1 = cmp->in(1);
   if( !i1->is_Phi() ) return NULL;
   PhiNode *phi = i1->as_Phi();
   if( phase->type( phi ) != TypeInt::BOOL )
     return NULL;
   // Check for diamond pattern
   int true_path = phi->is_diamond_phi();
   if( true_path == 0 ) return NULL;
   // Make sure that iff and the control of the phi are different. This
   // should really only happen for dead control flow since it requires
   // an illegal cycle.
   if (phi->in(0)->in(1)->in(0) == iff) return NULL;
   // phi->region->if_proj->ifnode->bool->cmp
   BoolNode *bol2 = phi->in(0)->in(1)->in(0)->in(1)->as_Bool();
   // Now get the 'sense' of the test correct so we can plug in
   // either iff2->in(1) or its complement.
   int flip = 0;
   if( bol->_test._test == BoolTest::ne ) flip = 1-flip;
   else if( bol->_test._test != BoolTest::eq ) return NULL;
   if( cmp2_t == TypeInt::ZERO ) flip = 1-flip;
   const Type *phi1_t = phase->type( phi->in(1) );
   const Type *phi2_t = phase->type( phi->in(2) );
   // Check for Phi(0,1) and flip
   if( phi1_t == TypeInt::ZERO ) {
     if( phi2_t != TypeInt::ONE ) return NULL;
     flip = 1-flip;
   } else {
     // Check for Phi(1,0)
     if( phi1_t != TypeInt::ONE  ) return NULL;
     if( phi2_t != TypeInt::ZERO ) return NULL;
   }
   if( true_path == 2 ) {
     flip = 1-flip;
   }
   Node* new_bol = (flip ? phase->transform( bol2->negate(phase) ) : bol2);
   assert(new_bol != iff->in(1), "must make progress");
   iff->set_req(1, new_bol);
   // Intervening diamond probably goes dead
   phase->C->set_major_progress();
   return iff;
 }
 static IfNode* idealize_test(PhaseGVN* phase, IfNode* iff);
 struct RangeCheck {
   Node* ctl;
   jint off;
 };
 //------------------------------Ideal------------------------------------------
 // Return a node which is more "ideal" than the current node.  Strip out
 // control copies
 Node *IfNode::Ideal(PhaseGVN *phase, bool can_reshape) {
   if (remove_dead_region(phase, can_reshape))  return this;
   // No Def-Use info?
   if (!can_reshape)  return NULL;
   PhaseIterGVN *igvn = phase->is_IterGVN();
   // Don't bother trying to transform a dead if
   if (in(0)->is_top())  return NULL;
   // Don't bother trying to transform an if with a dead test
   if (in(1)->is_top())  return NULL;
   // Another variation of a dead test
   if (in(1)->is_Con())  return NULL;
   // Another variation of a dead if
   if (outcnt() < 2)  return NULL;
   // Canonicalize the test.
   Node* idt_if = idealize_test(phase, this);
   if (idt_if != NULL)  return idt_if;
   // Try to split the IF
   Node *s = split_if(this, igvn);
   if (s != NULL)  return s;
   // Check for people making a useless boolean: things like
   // if( (x < y ? true : false) ) { ... }
   // Replace with if( x < y ) { ... }
   Node *bol2 = remove_useless_bool(this, phase);
   if( bol2 ) return bol2;
   // Setup to scan up the CFG looking for a dominating test
   Node *dom = in(0);
   Node *prev_dom = this;
   // Check for range-check vs other kinds of tests
   Node *index1, *range1;
   jint offset1;
   int flip1 = is_range_check(range1, index1, offset1);
   if( flip1 ) {
     // Try to remove extra range checks.  All 'up_one_dom' gives up at merges
     // so all checks we inspect post-dominate the top-most check we find.
     // If we are going to fail the current check and we reach the top check
     // then we are guaranteed to fail, so just start interpreting there.
     // We 'expand' the top 3 range checks to include all post-dominating
     // checks.
     // The top 3 range checks seen
     const int NRC =3;
     RangeCheck prev_checks[NRC];
     int nb_checks = 0;
     // Low and high offsets seen so far
     jint off_lo = offset1;
     jint off_hi = offset1;
     bool found_immediate_dominator = false;
     // Scan for the top checks and collect range of offsets
     for (int dist = 0; dist < 999; dist++) { // Range-Check scan limit
       if (dom->Opcode() == Op_If &&  // Not same opcode?
           prev_dom->in(0) == dom) { // One path of test does dominate?
         if (dom == this) return NULL; // dead loop
         // See if this is a range check
         Node *index2, *range2;
         jint offset2;
         int flip2 = dom->as_If()->is_range_check(range2, index2, offset2);
         // See if this is a _matching_ range check, checking against
         // the same array bounds.
         if (flip2 == flip1 && range2 == range1 && index2 == index1 &&
             dom->outcnt() == 2) {
           if (nb_checks == 0 && dom->in(1) == in(1)) {
             // Found an immediately dominating test at the same offset.
             // This kind of back-to-back test can be eliminated locally,
             // and there is no need to search further for dominating tests.
             assert(offset2 == offset1, "Same test but different offsets");
             found_immediate_dominator = true;
             break;
           }
           // Gather expanded bounds
           off_lo = MIN2(off_lo,offset2);
           off_hi = MAX2(off_hi,offset2);
           // Record top NRC range checks
           prev_checks[nb_checks%NRC].ctl = prev_dom;
           prev_checks[nb_checks%NRC].off = offset2;
           nb_checks++;
         }
       }
       prev_dom = dom;
       dom = up_one_dom(dom);
       if (!dom) break;
     }
     if (!found_immediate_dominator) {
       // Attempt to widen the dominating range check to cover some later
       // ones.  Since range checks "fail" by uncommon-trapping to the
       // interpreter, widening a check can make us speculatively enter
       // the interpreter.  If we see range-check deopt's, do not widen!
       if (!phase->C->allow_range_check_smearing())  return NULL;
       // Didn't find prior covering check, so cannot remove anything.
       if (nb_checks == 0) {
         return NULL;
       }
       // Constant indices only need to check the upper bound.
       // Non-constant indices must check both low and high.
       int chk0 = (nb_checks - 1) % NRC;
       if (index1) {
         if (nb_checks == 1) {
           return NULL;
         } else {
           // If the top range check's constant is the min or max of
           // all constants we widen the next one to cover the whole
           // range of constants.
           RangeCheck rc0 = prev_checks[chk0];
           int chk1 = (nb_checks - 2) % NRC;
           RangeCheck rc1 = prev_checks[chk1];
           if (rc0.off == off_lo) {
             adjust_check(rc1.ctl, range1, index1, flip1, off_hi, igvn);
             prev_dom = rc1.ctl;
           } else if (rc0.off == off_hi) {
             adjust_check(rc1.ctl, range1, index1, flip1, off_lo, igvn);
             prev_dom = rc1.ctl;
           } else {
             // If the top test's constant is not the min or max of all
             // constants, we need 3 range checks. We must leave the
             // top test unchanged because widening it would allow the
             // accesses it protects to successfully read/write out of
             // bounds.
             if (nb_checks == 2) {
               return NULL;
             }
             int chk2 = (nb_checks - 3) % NRC;
             RangeCheck rc2 = prev_checks[chk2];
             // The top range check a+i covers interval: -a <= i < length-a
             // The second range check b+i covers interval: -b <= i < length-b
             if (rc1.off <= rc0.off) {
               // if b <= a, we change the second range check to:
               // -min_of_all_constants <= i < length-min_of_all_constants
               // Together top and second range checks now cover:
               // -min_of_all_constants <= i < length-a
               // which is more restrictive than -b <= i < length-b:
               // -b <= -min_of_all_constants <= i < length-a <= length-b
               // The third check is then changed to:
               // -max_of_all_constants <= i < length-max_of_all_constants
               // so 2nd and 3rd checks restrict allowed values of i to:
               // -min_of_all_constants <= i < length-max_of_all_constants
               adjust_check(rc1.ctl, range1, index1, flip1, off_lo, igvn);
               adjust_check(rc2.ctl, range1, index1, flip1, off_hi, igvn);
             } else {
               // if b > a, we change the second range check to:
               // -max_of_all_constants <= i < length-max_of_all_constants
               // Together top and second range checks now cover:
               // -a <= i < length-max_of_all_constants
               // which is more restrictive than -b <= i < length-b:
               // -b < -a <= i < length-max_of_all_constants <= length-b
               // The third check is then changed to:
               // -max_of_all_constants <= i < length-max_of_all_constants
               // so 2nd and 3rd checks restrict allowed values of i to:
               // -min_of_all_constants <= i < length-max_of_all_constants
               adjust_check(rc1.ctl, range1, index1, flip1, off_hi, igvn);
               adjust_check(rc2.ctl, range1, index1, flip1, off_lo, igvn);
             }
             prev_dom = rc2.ctl;
           }
         }
       } else {
         RangeCheck rc0 = prev_checks[chk0];
         // 'Widen' the offset of the 1st and only covering check
         adjust_check(rc0.ctl, range1, index1, flip1, off_hi, igvn);
         // Test is now covered by prior checks, dominate it out
         prev_dom = rc0.ctl;
       }
     }
   } else {                      // Scan for an equivalent test
     Node *cmp;
     int dist = 0;               // Cutoff limit for search
     int op = Opcode();
     if( op == Op_If &&
         (cmp=in(1)->in(1))->Opcode() == Op_CmpP ) {
       if( cmp->in(2) != NULL && // make sure cmp is not already dead
           cmp->in(2)->bottom_type() == TypePtr::NULL_PTR ) {
         dist = 64;              // Limit for null-pointer scans
       } else {
         dist = 4;               // Do not bother for random pointer tests
       }
     } else {
       dist = 4;                 // Limit for random junky scans
     }
     // Normal equivalent-test check.
     if( !dom ) return NULL;     // Dead loop?
     Node* result = fold_compares(phase);
     if (result != NULL) {
       return result;
     }
     // Search up the dominator tree for an If with an identical test
     while( dom->Opcode() != op    ||  // Not same opcode?
            dom->in(1)    != in(1) ||  // Not same input 1?
            (req() == 3 && dom->in(2) != in(2)) || // Not same input 2?
            prev_dom->in(0) != dom ) { // One path of test does not dominate?
       if( dist < 0 ) return NULL;
       dist--;
       prev_dom = dom;
       dom = up_one_dom( dom );
       if( !dom ) return NULL;
     }
     // Check that we did not follow a loop back to ourselves
     if( this == dom )
       return NULL;
     if( dist > 2 )              // Add to count of NULL checks elided
       explicit_null_checks_elided++;
   } // End of Else scan for an equivalent test
   // Hit!  Remove this IF
 #ifndef PRODUCT
   if( TraceIterativeGVN ) {
     tty->print("   Removing IfNode: "); this->dump();
   }
   if( VerifyOpto && !phase->allow_progress() ) {
     // Found an equivalent dominating test,
     // we can not guarantee reaching a fix-point for these during iterativeGVN
     // since intervening nodes may not change.
     return NULL;
   }
 #endif
   // Replace dominated IfNode
   dominated_by( prev_dom, igvn );
   // Must return either the original node (now dead) or a new node
   // (Do not return a top here, since that would break the uniqueness of top.)
   return new (phase->C) ConINode(TypeInt::ZERO);
 }
 //------------------------------dominated_by-----------------------------------
 void IfNode::dominated_by( Node *prev_dom, PhaseIterGVN *igvn ) {
   igvn->hash_delete(this);      // Remove self to prevent spurious V-N
   Node *idom = in(0);
   // Need opcode to decide which way 'this' test goes
   int prev_op = prev_dom->Opcode();
   Node *top = igvn->C->top(); // Shortcut to top
   // Loop predicates may have depending checks which should not
   // be skipped. For example, range check predicate has two checks
   // for lower and upper bounds.
   ProjNode* unc_proj = proj_out(1 - prev_dom->as_Proj()->_con)->as_Proj();
   if ((unc_proj != NULL) && (unc_proj->is_uncommon_trap_proj(Deoptimization::Reason_predicate))) {
     prev_dom = idom;
   }
   // Now walk the current IfNode's projections.
   // Loop ends when 'this' has no more uses.
   for (DUIterator_Last imin, i = last_outs(imin); i >= imin; --i) {
     Node *ifp = last_out(i);     // Get IfTrue/IfFalse
     igvn->add_users_to_worklist(ifp);
     // Check which projection it is and set target.
     // Data-target is either the dominating projection of the same type
     // or TOP if the dominating projection is of opposite type.
     // Data-target will be used as the new control edge for the non-CFG
     // nodes like Casts and Loads.
     Node *data_target = (ifp->Opcode() == prev_op) ? prev_dom : top;
     // Control-target is just the If's immediate dominator or TOP.
     Node *ctrl_target = (ifp->Opcode() == prev_op) ?     idom : top;
     // For each child of an IfTrue/IfFalse projection, reroute.
     // Loop ends when projection has no more uses.
     for (DUIterator_Last jmin, j = ifp->last_outs(jmin); j >= jmin; --j) {
       Node* s = ifp->last_out(j);   // Get child of IfTrue/IfFalse
       if( !s->depends_only_on_test() ) {
         // Find the control input matching this def-use edge.
         // For Regions it may not be in slot 0.
         uint l;
         for( l = 0; s->in(l) != ifp; l++ ) { }
         igvn->replace_input_of(s, l, ctrl_target);
       } else {                      // Else, for control producers,
         igvn->replace_input_of(s, 0, data_target); // Move child to data-target
       }
     } // End for each child of a projection
     igvn->remove_dead_node(ifp);
   } // End for each IfTrue/IfFalse child of If
   // Kill the IfNode
   igvn->remove_dead_node(this);
 }
 //------------------------------Identity---------------------------------------
 // If the test is constant & we match, then we are the input Control
 Node *IfTrueNode::Identity( PhaseTransform *phase ) {
   // Can only optimize if cannot go the other way
   const TypeTuple *t = phase->type(in(0))->is_tuple();
   return ( t == TypeTuple::IFNEITHER || t == TypeTuple::IFTRUE )
     ? in(0)->in(0)              // IfNode control
     : this;                     // no progress
 }
 //------------------------------dump_spec--------------------------------------
 #ifndef PRODUCT
 void IfNode::dump_spec(outputStream *st) const {
   st->print("P=%f, C=%f",_prob,_fcnt);
 }
 #endif
 //------------------------------idealize_test----------------------------------
 // Try to canonicalize tests better.  Peek at the Cmp/Bool/If sequence and
 // come up with a canonical sequence.  Bools getting 'eq', 'gt' and 'ge' forms
 // converted to 'ne', 'le' and 'lt' forms.  IfTrue/IfFalse get swapped as
 // needed.
 static IfNode* idealize_test(PhaseGVN* phase, IfNode* iff) {
   assert(iff->in(0) != NULL, "If must be live");
   if (iff->outcnt() != 2)  return NULL; // Malformed projections.
   Node* old_if_f = iff->proj_out(false);
   Node* old_if_t = iff->proj_out(true);
   // CountedLoopEnds want the back-control test to be TRUE, irregardless of
   // whether they are testing a 'gt' or 'lt' condition.  The 'gt' condition
   // happens in count-down loops
   if (iff->is_CountedLoopEnd())  return NULL;
   if (!iff->in(1)->is_Bool())  return NULL; // Happens for partially optimized IF tests
   BoolNode *b = iff->in(1)->as_Bool();
   BoolTest bt = b->_test;
   // Test already in good order?
   if( bt.is_canonical() )
     return NULL;
   // Flip test to be canonical.  Requires flipping the IfFalse/IfTrue and
   // cloning the IfNode.
   Node* new_b = phase->transform( new (phase->C) BoolNode(b->in(1), bt.negate()) );
   if( !new_b->is_Bool() ) return NULL;
   b = new_b->as_Bool();
   PhaseIterGVN *igvn = phase->is_IterGVN();
   assert( igvn, "Test is not canonical in parser?" );
   // The IF node never really changes, but it needs to be cloned
   iff = new (phase->C) IfNode( iff->in(0), b, 1.0-iff->_prob, iff->_fcnt);
   Node *prior = igvn->hash_find_insert(iff);
   if( prior ) {
     igvn->remove_dead_node(iff);
     iff = (IfNode*)prior;
   } else {
     // Cannot call transform on it just yet
     igvn->set_type_bottom(iff);
   }
   igvn->_worklist.push(iff);
   // Now handle projections.  Cloning not required.
   Node* new_if_f = (Node*)(new (phase->C) IfFalseNode( iff ));
   Node* new_if_t = (Node*)(new (phase->C) IfTrueNode ( iff ));
   igvn->register_new_node_with_optimizer(new_if_f);
   igvn->register_new_node_with_optimizer(new_if_t);
   // Flip test, so flip trailing control
   igvn->replace_node(old_if_f, new_if_t);
   igvn->replace_node(old_if_t, new_if_f);
   // Progress
   return iff;
 }
 //------------------------------Identity---------------------------------------
 // If the test is constant & we match, then we are the input Control
 Node *IfFalseNode::Identity( PhaseTransform *phase ) {
   // Can only optimize if cannot go the other way
   const TypeTuple *t = phase->type(in(0))->is_tuple();
   return ( t == TypeTuple::IFNEITHER || t == TypeTuple::IFFALSE )
     ? in(0)->in(0)              // IfNode control
     : this;                     // no progress
 }

Mercurial > jdk8-mips64-public > hotspot / annotate

src/share/vm/opto/ifnode.cpp@09d0d56ca735 (annotated)

src/share/vm/opto/ifnode.cpp