1 /*

     2  * Copyright (c) 2002, 2016, Oracle and/or its affiliates. All rights reserved.

     3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

     4  *

     5  * This code is free software; you can redistribute it and/or modify it

     6  * under the terms of the GNU General Public License version 2 only, as

     7  * published by the Free Software Foundation.

     8  *

     9  * This code is distributed in the hope that it will be useful, but WITHOUT

    10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

    11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

    12  * version 2 for more details (a copy is included in the LICENSE file that

    13  * accompanied this code).

    14  *

    15  * You should have received a copy of the GNU General Public License version

    16  * 2 along with this work; if not, write to the Free Software Foundation,

    17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

    18  *

    19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

    20  * or visit www.oracle.com if you need additional information or have any

    21  * questions.

    22  *

    23  */

    24 

    25 #include "precompiled.hpp"

    26 #include "code/vmreg.inline.hpp"

    27 #include "compiler/oopMap.hpp"

    28 #include "memory/resourceArea.hpp"

    29 #include "opto/addnode.hpp"

    30 #include "opto/callnode.hpp"

    31 #include "opto/compile.hpp"

    32 #include "opto/machnode.hpp"

    33 #include "opto/matcher.hpp"

    34 #include "opto/phase.hpp"

    35 #include "opto/regalloc.hpp"

    36 #include "opto/rootnode.hpp"

    37 #include "utilities/align.hpp"

    38 

    39 // The functions in this file builds OopMaps after all scheduling is done.

    40 //

    41 // OopMaps contain a list of all registers and stack-slots containing oops (so

    42 // they can be updated by GC).  OopMaps also contain a list of derived-pointer

    43 // base-pointer pairs.  When the base is moved, the derived pointer moves to

    44 // follow it.  Finally, any registers holding callee-save values are also

    45 // recorded.  These might contain oops, but only the caller knows.

    46 //

    47 // BuildOopMaps implements a simple forward reaching-defs solution.  At each

    48 // GC point we'll have the reaching-def Nodes.  If the reaching Nodes are

    49 // typed as pointers (no offset), then they are oops.  Pointers+offsets are

    50 // derived pointers, and bases can be found from them.  Finally, we'll also

    51 // track reaching callee-save values.  Note that a copy of a callee-save value

    52 // "kills" it's source, so that only 1 copy of a callee-save value is alive at

    53 // a time.

    54 //

    55 // We run a simple bitvector liveness pass to help trim out dead oops.  Due to

    56 // irreducible loops, we can have a reaching def of an oop that only reaches

    57 // along one path and no way to know if it's valid or not on the other path.

    58 // The bitvectors are quite dense and the liveness pass is fast.

    59 //

    60 // At GC points, we consult this information to build OopMaps.  All reaching

    61 // defs typed as oops are added to the OopMap.  Only 1 instance of a

    62 // callee-save register can be recorded.  For derived pointers, we'll have to

    63 // find and record the register holding the base.

    64 //

    65 // The reaching def's is a simple 1-pass worklist approach.  I tried a clever

    66 // breadth-first approach but it was worse (showed O(n^2) in the

    67 // pick-next-block code).

    68 //

    69 // The relevant data is kept in a struct of arrays (it could just as well be

    70 // an array of structs, but the struct-of-arrays is generally a little more

    71 // efficient).  The arrays are indexed by register number (including

    72 // stack-slots as registers) and so is bounded by 200 to 300 elements in

    73 // practice.  One array will map to a reaching def Node (or NULL for

    74 // conflict/dead).  The other array will map to a callee-saved register or

    75 // OptoReg::Bad for not-callee-saved.

    76 

    77 

    78 // Structure to pass around

    79 struct OopFlow : public ResourceObj {

    80   short *_callees;              // Array mapping register to callee-saved

    81   Node **_defs;                 // array mapping register to reaching def

    82                                 // or NULL if dead/conflict

    83   // OopFlow structs, when not being actively modified, describe the _end_ of

    84   // this block.

    85   Block *_b;                    // Block for this struct

    86   OopFlow *_next;               // Next free OopFlow

    87                                 // or NULL if dead/conflict

    88   Compile* C;

    89 

    90   OopFlow( short *callees, Node **defs, Compile* c ) : _callees(callees), _defs(defs),

    91     _b(NULL), _next(NULL), C(c) { }

    92 

    93   // Given reaching-defs for this block start, compute it for this block end

    94   void compute_reach( PhaseRegAlloc *regalloc, int max_reg, Dict *safehash );

    95 

    96   // Merge these two OopFlows into the 'this' pointer.

    97   void merge( OopFlow *flow, int max_reg );

    98 

    99   // Copy a 'flow' over an existing flow

   100   void clone( OopFlow *flow, int max_size);

   101 

   102   // Make a new OopFlow from scratch

   103   static OopFlow *make( Arena *A, int max_size, Compile* C );

   104 

   105   // Build an oopmap from the current flow info

   106   OopMap *build_oop_map( Node *n, int max_reg, PhaseRegAlloc *regalloc, int* live );

   107 };

   108 

   109 // Given reaching-defs for this block start, compute it for this block end

   110 void OopFlow::compute_reach( PhaseRegAlloc *regalloc, int max_reg, Dict *safehash ) {

   111 

   112   for( uint i=0; i<_b->number_of_nodes(); i++ ) {

   113     Node *n = _b->get_node(i);

   114 

   115     if( n->jvms() ) {           // Build an OopMap here?

   116       JVMState *jvms = n->jvms();

   117       // no map needed for leaf calls

   118       if( n->is_MachSafePoint() && !n->is_MachCallLeaf() ) {

   119         int *live = (int*) (*safehash)[n];

   120         assert( live, "must find live" );

   121         n->as_MachSafePoint()->set_oop_map( build_oop_map(n,max_reg,regalloc, live) );

   122       }

   123     }

   124 

   125     // Assign new reaching def's.

   126     // Note that I padded the _defs and _callees arrays so it's legal

   127     // to index at _defs[OptoReg::Bad].

   128     OptoReg::Name first = regalloc->get_reg_first(n);

   129     OptoReg::Name second = regalloc->get_reg_second(n);

   130     _defs[first] = n;

   131     _defs[second] = n;

   132 

   133     // Pass callee-save info around copies

   134     int idx = n->is_Copy();

   135     if( idx ) {                 // Copies move callee-save info

   136       OptoReg::Name old_first = regalloc->get_reg_first(n->in(idx));

   137       OptoReg::Name old_second = regalloc->get_reg_second(n->in(idx));

   138       int tmp_first = _callees[old_first];

   139       int tmp_second = _callees[old_second];

   140       _callees[old_first] = OptoReg::Bad; // callee-save is moved, dead in old location

   141       _callees[old_second] = OptoReg::Bad;

   142       _callees[first] = tmp_first;

   143       _callees[second] = tmp_second;

   144     } else if( n->is_Phi() ) {  // Phis do not mod callee-saves

   145       assert( _callees[first] == _callees[regalloc->get_reg_first(n->in(1))], "" );

   146       assert( _callees[second] == _callees[regalloc->get_reg_second(n->in(1))], "" );

   147       assert( _callees[first] == _callees[regalloc->get_reg_first(n->in(n->req()-1))], "" );

   148       assert( _callees[second] == _callees[regalloc->get_reg_second(n->in(n->req()-1))], "" );

   149     } else {

   150       _callees[first] = OptoReg::Bad; // No longer holding a callee-save value

   151       _callees[second] = OptoReg::Bad;

   152 

   153       // Find base case for callee saves

   154       if( n->is_Proj() && n->in(0)->is_Start() ) {

   155         if( OptoReg::is_reg(first) &&

   156             regalloc->_matcher.is_save_on_entry(first) )

   157           _callees[first] = first;

   158         if( OptoReg::is_reg(second) &&

   159             regalloc->_matcher.is_save_on_entry(second) )

   160           _callees[second] = second;

   161       }

   162     }

   163   }

   164 }

   165 

   166 // Merge the given flow into the 'this' flow

   167 void OopFlow::merge( OopFlow *flow, int max_reg ) {

   168   assert( _b == NULL, "merging into a happy flow" );

   169   assert( flow->_b, "this flow is still alive" );

   170   assert( flow != this, "no self flow" );

   171 

   172   // Do the merge.  If there are any differences, drop to 'bottom' which

   173   // is OptoReg::Bad or NULL depending.

   174   for( int i=0; i<max_reg; i++ ) {

   175     // Merge the callee-save's

   176     if( _callees[i] != flow->_callees[i] )

   177       _callees[i] = OptoReg::Bad;

   178     // Merge the reaching defs

   179     if( _defs[i] != flow->_defs[i] )

   180       _defs[i] = NULL;

   181   }

   182 

   183 }

   184 

   185 void OopFlow::clone( OopFlow *flow, int max_size ) {

   186   _b = flow->_b;

   187   memcpy( _callees, flow->_callees, sizeof(short)*max_size);

   188   memcpy( _defs   , flow->_defs   , sizeof(Node*)*max_size);

   189 }

   190 

   191 OopFlow *OopFlow::make( Arena *A, int max_size, Compile* C ) {

   192   short *callees = NEW_ARENA_ARRAY(A,short,max_size+1);

   193   Node **defs    = NEW_ARENA_ARRAY(A,Node*,max_size+1);

   194   debug_only( memset(defs,0,(max_size+1)*sizeof(Node*)) );

   195   OopFlow *flow = new (A) OopFlow(callees+1, defs+1, C);

   196   assert( &flow->_callees[OptoReg::Bad] == callees, "Ok to index at OptoReg::Bad" );

   197   assert( &flow->_defs   [OptoReg::Bad] == defs   , "Ok to index at OptoReg::Bad" );

   198   return flow;

   199 }

   200 

   201 static int get_live_bit( int *live, int reg ) {

   202   return live[reg>>LogBitsPerInt] &   (1<<(reg&(BitsPerInt-1))); }

   203 static void set_live_bit( int *live, int reg ) {

   204          live[reg>>LogBitsPerInt] |=  (1<<(reg&(BitsPerInt-1))); }

   205 static void clr_live_bit( int *live, int reg ) {

   206          live[reg>>LogBitsPerInt] &= ~(1<<(reg&(BitsPerInt-1))); }

   207 

   208 // Build an oopmap from the current flow info

   209 OopMap *OopFlow::build_oop_map( Node *n, int max_reg, PhaseRegAlloc *regalloc, int* live ) {

   210   int framesize = regalloc->_framesize;

   211   int max_inarg_slot = OptoReg::reg2stack(regalloc->_matcher._new_SP);

   212   debug_only( char *dup_check = NEW_RESOURCE_ARRAY(char,OptoReg::stack0());

   213               memset(dup_check,0,OptoReg::stack0()) );

   214 

   215   OopMap *omap = new OopMap( framesize,  max_inarg_slot );

   216   MachCallNode *mcall = n->is_MachCall() ? n->as_MachCall() : NULL;

   217   JVMState* jvms = n->jvms();

   218 

   219   // For all registers do...

   220   for( int reg=0; reg<max_reg; reg++ ) {

   221     if( get_live_bit(live,reg) == 0 )

   222       continue;                 // Ignore if not live

   223 

   224     // %%% C2 can use 2 OptoRegs when the physical register is only one 64bit

   225     // register in that case we'll get an non-concrete register for the second

   226     // half. We only need to tell the map the register once!

   227     //

   228     // However for the moment we disable this change and leave things as they

   229     // were.

   230 

   231     VMReg r = OptoReg::as_VMReg(OptoReg::Name(reg), framesize, max_inarg_slot);

   232 

   233     if (false && r->is_reg() && !r->is_concrete()) {

   234       continue;

   235     }

   236 

   237     // See if dead (no reaching def).

   238     Node *def = _defs[reg];     // Get reaching def

   239     assert( def, "since live better have reaching def" );

   240 

   241     // Classify the reaching def as oop, derived, callee-save, dead, or other

   242     const Type *t = def->bottom_type();

   243     if( t->isa_oop_ptr() ) {    // Oop or derived?

   244       assert( !OptoReg::is_valid(_callees[reg]), "oop can't be callee save" );

   245 #ifdef _LP64

   246       // 64-bit pointers record oop-ishness on 2 aligned adjacent registers.

   247       // Make sure both are record from the same reaching def, but do not

   248       // put both into the oopmap.

   249       if( (reg&1) == 1 ) {      // High half of oop-pair?

   250         assert( _defs[reg-1] == _defs[reg], "both halves from same reaching def" );

   251         continue;               // Do not record high parts in oopmap

   252       }

   253 #endif

   254 

   255       // Check for a legal reg name in the oopMap and bailout if it is not.

   256       if (!omap->legal_vm_reg_name(r)) {

   257         regalloc->C->record_method_not_compilable("illegal oopMap register name");

   258         continue;

   259       }

   260       if( t->is_ptr()->_offset == 0 ) { // Not derived?

   261         if( mcall ) {

   262           // Outgoing argument GC mask responsibility belongs to the callee,

   263           // not the caller.  Inspect the inputs to the call, to see if

   264           // this live-range is one of them.

   265           uint cnt = mcall->tf()->domain()->cnt();

   266           uint j;

   267           for( j = TypeFunc::Parms; j < cnt; j++)

   268             if( mcall->in(j) == def )

   269               break;            // reaching def is an argument oop

   270           if( j < cnt )         // arg oops dont go in GC map

   271             continue;           // Continue on to the next register

   272         }

   273         omap->set_oop(r);

   274       } else {                  // Else it's derived.

   275         // Find the base of the derived value.

   276         uint i;

   277         // Fast, common case, scan

   278         for( i = jvms->oopoff(); i < n->req(); i+=2 )

   279           if( n->in(i) == def ) break; // Common case

   280         if( i == n->req() ) {   // Missed, try a more generous scan

   281           // Scan again, but this time peek through copies

   282           for( i = jvms->oopoff(); i < n->req(); i+=2 ) {

   283             Node *m = n->in(i); // Get initial derived value

   284             while( 1 ) {

   285               Node *d = def;    // Get initial reaching def

   286               while( 1 ) {      // Follow copies of reaching def to end

   287                 if( m == d ) goto found; // breaks 3 loops

   288                 int idx = d->is_Copy();

   289                 if( !idx ) break;

   290                 d = d->in(idx);     // Link through copy

   291               }

   292               int idx = m->is_Copy();

   293               if( !idx ) break;

   294               m = m->in(idx);

   295             }

   296           }

   297           guarantee( 0, "must find derived/base pair" );

   298         }

   299       found: ;

   300         Node *base = n->in(i+1); // Base is other half of pair

   301         int breg = regalloc->get_reg_first(base);

   302         VMReg b = OptoReg::as_VMReg(OptoReg::Name(breg), framesize, max_inarg_slot);

   303 

   304         // I record liveness at safepoints BEFORE I make the inputs

   305         // live.  This is because argument oops are NOT live at a

   306         // safepoint (or at least they cannot appear in the oopmap).

   307         // Thus bases of base/derived pairs might not be in the

   308         // liveness data but they need to appear in the oopmap.

   309         if( get_live_bit(live,breg) == 0 ) {// Not live?

   310           // Flag it, so next derived pointer won't re-insert into oopmap

   311           set_live_bit(live,breg);

   312           // Already missed our turn?

   313           if( breg < reg ) {

   314             if (b->is_stack() || b->is_concrete() || true ) {

   315               omap->set_oop( b);

   316             }

   317           }

   318         }

   319         if (b->is_stack() || b->is_concrete() || true ) {

   320           omap->set_derived_oop( r, b);

   321         }

   322       }

   323 

   324     } else if( t->isa_narrowoop() ) {

   325       assert( !OptoReg::is_valid(_callees[reg]), "oop can't be callee save" );

   326       // Check for a legal reg name in the oopMap and bailout if it is not.

   327       if (!omap->legal_vm_reg_name(r)) {

   328         regalloc->C->record_method_not_compilable("illegal oopMap register name");

   329         continue;

   330       }

   331       if( mcall ) {

   332           // Outgoing argument GC mask responsibility belongs to the callee,

   333           // not the caller.  Inspect the inputs to the call, to see if

   334           // this live-range is one of them.

   335         uint cnt = mcall->tf()->domain()->cnt();

   336         uint j;

   337         for( j = TypeFunc::Parms; j < cnt; j++)

   338           if( mcall->in(j) == def )

   339             break;            // reaching def is an argument oop

   340         if( j < cnt )         // arg oops dont go in GC map

   341           continue;           // Continue on to the next register

   342       }

   343       omap->set_narrowoop(r);

   344     } else if( OptoReg::is_valid(_callees[reg])) { // callee-save?

   345       // It's a callee-save value

   346       assert( dup_check[_callees[reg]]==0, "trying to callee save same reg twice" );

   347       debug_only( dup_check[_callees[reg]]=1; )

   348       VMReg callee = OptoReg::as_VMReg(OptoReg::Name(_callees[reg]));

   349       if ( callee->is_concrete() || true ) {

   350         omap->set_callee_saved( r, callee);

   351       }

   352 

   353     } else {

   354       // Other - some reaching non-oop value

   355       omap->set_value( r);

   356 #ifdef ASSERT

   357       if( t->isa_rawptr() && C->cfg()->_raw_oops.member(def) ) {

   358         def->dump();

   359         n->dump();

   360         assert(false, "there should be a oop in OopMap instead of a live raw oop at safepoint");

   361       }

   362 #endif

   363     }

   364 

   365   }

   366 

   367 #ifdef ASSERT

   368   /* Nice, Intel-only assert

   369   int cnt_callee_saves=0;

   370   int reg2 = 0;

   371   while (OptoReg::is_reg(reg2)) {

   372     if( dup_check[reg2] != 0) cnt_callee_saves++;

   373     assert( cnt_callee_saves==3 || cnt_callee_saves==5, "missed some callee-save" );

   374     reg2++;

   375   }

   376   */

   377 #endif

   378 

   379 #ifdef ASSERT

   380   for( OopMapStream oms1(omap, OopMapValue::derived_oop_value); !oms1.is_done(); oms1.next()) {

   381     OopMapValue omv1 = oms1.current();

   382     bool found = false;

   383     for( OopMapStream oms2(omap,OopMapValue::oop_value); !oms2.is_done(); oms2.next()) {

   384       if( omv1.content_reg() == oms2.current().reg() ) {

   385         found = true;

   386         break;

   387       }

   388     }

   389     assert( found, "derived with no base in oopmap" );

   390   }

   391 #endif

   392 

   393   return omap;

   394 }

   395 

   396 // Compute backwards liveness on registers

   397 static void do_liveness(PhaseRegAlloc* regalloc, PhaseCFG* cfg, Block_List* worklist, int max_reg_ints, Arena* A, Dict* safehash) {

   398   int* live = NEW_ARENA_ARRAY(A, int, (cfg->number_of_blocks() + 1) * max_reg_ints);

   399   int* tmp_live = &live[cfg->number_of_blocks() * max_reg_ints];

   400   Node* root = cfg->get_root_node();

   401   // On CISC platforms, get the node representing the stack pointer  that regalloc

   402   // used for spills

   403   Node *fp = NodeSentinel;

   404   if (UseCISCSpill && root->req() > 1) {

   405     fp = root->in(1)->in(TypeFunc::FramePtr);

   406   }

   407   memset(live, 0, cfg->number_of_blocks() * (max_reg_ints << LogBytesPerInt));

   408   // Push preds onto worklist

   409   for (uint i = 1; i < root->req(); i++) {

   410     Block* block = cfg->get_block_for_node(root->in(i));

   411     worklist->push(block);

   412   }

   413 

   414   // ZKM.jar includes tiny infinite loops which are unreached from below.

   415   // If we missed any blocks, we'll retry here after pushing all missed

   416   // blocks on the worklist.  Normally this outer loop never trips more

   417   // than once.

   418   while (1) {

   419 

   420     while( worklist->size() ) { // Standard worklist algorithm

   421       Block *b = worklist->rpop();

   422 

   423       // Copy first successor into my tmp_live space

   424       int s0num = b->_succs[0]->_pre_order;

   425       int *t = &live[s0num*max_reg_ints];

   426       for( int i=0; i<max_reg_ints; i++ )

   427         tmp_live[i] = t[i];

   428 

   429       // OR in the remaining live registers

   430       for( uint j=1; j<b->_num_succs; j++ ) {

   431         uint sjnum = b->_succs[j]->_pre_order;

   432         int *t = &live[sjnum*max_reg_ints];

   433         for( int i=0; i<max_reg_ints; i++ )

   434           tmp_live[i] |= t[i];

   435       }

   436 

   437       // Now walk tmp_live up the block backwards, computing live

   438       for( int k=b->number_of_nodes()-1; k>=0; k-- ) {

   439         Node *n = b->get_node(k);

   440         // KILL def'd bits

   441         int first = regalloc->get_reg_first(n);

   442         int second = regalloc->get_reg_second(n);

   443         if( OptoReg::is_valid(first) ) clr_live_bit(tmp_live,first);

   444         if( OptoReg::is_valid(second) ) clr_live_bit(tmp_live,second);

   445 

   446         MachNode *m = n->is_Mach() ? n->as_Mach() : NULL;

   447 

   448         // Check if m is potentially a CISC alternate instruction (i.e, possibly

   449         // synthesized by RegAlloc from a conventional instruction and a

   450         // spilled input)

   451         bool is_cisc_alternate = false;

   452         if (UseCISCSpill && m) {

   453           is_cisc_alternate = m->is_cisc_alternate();

   454         }

   455 

   456         // GEN use'd bits

   457         for( uint l=1; l<n->req(); l++ ) {

   458           Node *def = n->in(l);

   459           assert(def != 0, "input edge required");

   460           int first = regalloc->get_reg_first(def);

   461           int second = regalloc->get_reg_second(def);

   462           if( OptoReg::is_valid(first) ) set_live_bit(tmp_live,first);

   463           if( OptoReg::is_valid(second) ) set_live_bit(tmp_live,second);

   464           // If we use the stack pointer in a cisc-alternative instruction,

   465           // check for use as a memory operand.  Then reconstruct the RegName

   466           // for this stack location, and set the appropriate bit in the

   467           // live vector 4987749.

   468           if (is_cisc_alternate && def == fp) {

   469             const TypePtr *adr_type = NULL;

   470             intptr_t offset;

   471             const Node* base = m->get_base_and_disp(offset, adr_type);

   472             if (base == NodeSentinel) {

   473               // Machnode has multiple memory inputs. We are unable to reason

   474               // with these, but are presuming (with trepidation) that not any of

   475               // them are oops. This can be fixed by making get_base_and_disp()

   476               // look at a specific input instead of all inputs.

   477               assert(!def->bottom_type()->isa_oop_ptr(), "expecting non-oop mem input");

   478             } else if (base != fp || offset == Type::OffsetBot) {

   479               // Do nothing: the fp operand is either not from a memory use

   480               // (base == NULL) OR the fp is used in a non-memory context

   481               // (base is some other register) OR the offset is not constant,

   482               // so it is not a stack slot.

   483             } else {

   484               assert(offset >= 0, "unexpected negative offset");

   485               offset -= (offset % jintSize);  // count the whole word

   486               int stack_reg = regalloc->offset2reg(offset);

   487               if (OptoReg::is_stack(stack_reg)) {

   488                 set_live_bit(tmp_live, stack_reg);

   489               } else {

   490                 assert(false, "stack_reg not on stack?");

   491               }

   492             }

   493           }

   494         }

   495 

   496         if( n->jvms() ) {       // Record liveness at safepoint

   497 

   498           // This placement of this stanza means inputs to calls are

   499           // considered live at the callsite's OopMap.  Argument oops are

   500           // hence live, but NOT included in the oopmap.  See cutout in

   501           // build_oop_map.  Debug oops are live (and in OopMap).

   502           int *n_live = NEW_ARENA_ARRAY(A, int, max_reg_ints);

   503           for( int l=0; l<max_reg_ints; l++ )

   504             n_live[l] = tmp_live[l];

   505           safehash->Insert(n,n_live);

   506         }

   507 

   508       }

   509 

   510       // Now at block top, see if we have any changes.  If so, propagate

   511       // to prior blocks.

   512       int *old_live = &live[b->_pre_order*max_reg_ints];

   513       int l;

   514       for( l=0; l<max_reg_ints; l++ )

   515         if( tmp_live[l] != old_live[l] )

   516           break;

   517       if( l<max_reg_ints ) {     // Change!

   518         // Copy in new value

   519         for( l=0; l<max_reg_ints; l++ )

   520           old_live[l] = tmp_live[l];

   521         // Push preds onto worklist

   522         for (l = 1; l < (int)b->num_preds(); l++) {

   523           Block* block = cfg->get_block_for_node(b->pred(l));

   524           worklist->push(block);

   525         }

   526       }

   527     }

   528 

   529     // Scan for any missing safepoints.  Happens to infinite loops

   530     // ala ZKM.jar

   531     uint i;

   532     for (i = 1; i < cfg->number_of_blocks(); i++) {

   533       Block* block = cfg->get_block(i);

   534       uint j;

   535       for (j = 1; j < block->number_of_nodes(); j++) {

   536         if (block->get_node(j)->jvms() && (*safehash)[block->get_node(j)] == NULL) {

   537            break;

   538         }

   539       }

   540       if (j < block->number_of_nodes()) {

   541         break;

   542       }

   543     }

   544     if (i == cfg->number_of_blocks()) {

   545       break;                    // Got 'em all

   546     }

   547 

   548     if (PrintOpto && Verbose) {

   549       tty->print_cr("retripping live calc");

   550     }

   551 

   552     // Force the issue (expensively): recheck everybody

   553     for (i = 1; i < cfg->number_of_blocks(); i++) {

   554       worklist->push(cfg->get_block(i));

   555     }

   556   }

   557 }

   558 

   559 // Collect GC mask info - where are all the OOPs?

   560 void Compile::BuildOopMaps() {

   561   TracePhase tp("bldOopMaps", &timers[_t_buildOopMaps]);

   562   // Can't resource-mark because I need to leave all those OopMaps around,

   563   // or else I need to resource-mark some arena other than the default.

   564   // ResourceMark rm;              // Reclaim all OopFlows when done

   565   int max_reg = _regalloc->_max_reg; // Current array extent

   566 

   567   Arena *A = Thread::current()->resource_area();

   568   Block_List worklist;          // Worklist of pending blocks

   569 

   570   int max_reg_ints = align_up(max_reg, BitsPerInt)>>LogBitsPerInt;

   571   Dict *safehash = NULL;        // Used for assert only

   572   // Compute a backwards liveness per register.  Needs a bitarray of

   573   // #blocks x (#registers, rounded up to ints)

   574   safehash = new Dict(cmpkey,hashkey,A);

   575   do_liveness( _regalloc, _cfg, &worklist, max_reg_ints, A, safehash );

   576   OopFlow *free_list = NULL;    // Free, unused

   577 

   578   // Array mapping blocks to completed oopflows

   579   OopFlow **flows = NEW_ARENA_ARRAY(A, OopFlow*, _cfg->number_of_blocks());

   580   memset( flows, 0, _cfg->number_of_blocks() * sizeof(OopFlow*) );

   581 

   582 

   583   // Do the first block 'by hand' to prime the worklist

   584   Block *entry = _cfg->get_block(1);

   585   OopFlow *rootflow = OopFlow::make(A,max_reg,this);

   586   // Initialize to 'bottom' (not 'top')

   587   memset( rootflow->_callees, OptoReg::Bad, max_reg*sizeof(short) );

   588   memset( rootflow->_defs   ,            0, max_reg*sizeof(Node*) );

   589   flows[entry->_pre_order] = rootflow;

   590 

   591   // Do the first block 'by hand' to prime the worklist

   592   rootflow->_b = entry;

   593   rootflow->compute_reach( _regalloc, max_reg, safehash );

   594   for( uint i=0; i<entry->_num_succs; i++ )

   595     worklist.push(entry->_succs[i]);

   596 

   597   // Now worklist contains blocks which have some, but perhaps not all,

   598   // predecessors visited.

   599   while( worklist.size() ) {

   600     // Scan for a block with all predecessors visited, or any randoms slob

   601     // otherwise.  All-preds-visited order allows me to recycle OopFlow

   602     // structures rapidly and cut down on the memory footprint.

   603     // Note: not all predecessors might be visited yet (must happen for

   604     // irreducible loops).  This is OK, since every live value must have the

   605     // SAME reaching def for the block, so any reaching def is OK.

   606     uint i;

   607 

   608     Block *b = worklist.pop();

   609     // Ignore root block

   610     if (b == _cfg->get_root_block()) {

   611       continue;

   612     }

   613     // Block is already done?  Happens if block has several predecessors,

   614     // he can get on the worklist more than once.

   615     if( flows[b->_pre_order] ) continue;

   616 

   617     // If this block has a visited predecessor AND that predecessor has this

   618     // last block as his only undone child, we can move the OopFlow from the

   619     // pred to this block.  Otherwise we have to grab a new OopFlow.

   620     OopFlow *flow = NULL;       // Flag for finding optimized flow

   621     Block *pred = (Block*)0xdeadbeef;

   622     // Scan this block's preds to find a done predecessor

   623     for (uint j = 1; j < b->num_preds(); j++) {

   624       Block* p = _cfg->get_block_for_node(b->pred(j));

   625       OopFlow *p_flow = flows[p->_pre_order];

   626       if( p_flow ) {            // Predecessor is done

   627         assert( p_flow->_b == p, "cross check" );

   628         pred = p;               // Record some predecessor

   629         // If all successors of p are done except for 'b', then we can carry

   630         // p_flow forward to 'b' without copying, otherwise we have to draw

   631         // from the free_list and clone data.

   632         uint k;

   633         for( k=0; k<p->_num_succs; k++ )

   634           if( !flows[p->_succs[k]->_pre_order] &&

   635               p->_succs[k] != b )

   636             break;

   637 

   638         // Either carry-forward the now-unused OopFlow for b's use

   639         // or draw a new one from the free list

   640         if( k==p->_num_succs ) {

   641           flow = p_flow;

   642           break;                // Found an ideal pred, use him

   643         }

   644       }

   645     }

   646 

   647     if( flow ) {

   648       // We have an OopFlow that's the last-use of a predecessor.

   649       // Carry it forward.

   650     } else {                    // Draw a new OopFlow from the freelist

   651       if( !free_list )

   652         free_list = OopFlow::make(A,max_reg,C);

   653       flow = free_list;

   654       assert( flow->_b == NULL, "oopFlow is not free" );

   655       free_list = flow->_next;

   656       flow->_next = NULL;

   657 

   658       // Copy/clone over the data

   659       flow->clone(flows[pred->_pre_order], max_reg);

   660     }

   661 

   662     // Mark flow for block.  Blocks can only be flowed over once,

   663     // because after the first time they are guarded from entering

   664     // this code again.

   665     assert( flow->_b == pred, "have some prior flow" );

   666     flow->_b = NULL;

   667 

   668     // Now push flow forward

   669     flows[b->_pre_order] = flow;// Mark flow for this block

   670     flow->_b = b;

   671     flow->compute_reach( _regalloc, max_reg, safehash );

   672 

   673     // Now push children onto worklist

   674     for( i=0; i<b->_num_succs; i++ )

   675       worklist.push(b->_succs[i]);

   676 

   677   }

   678 }