rev 10504 : value type calling convention

   1 /*
   2  * Copyright (c) 2002, 2014, 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.
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  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).
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  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
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  24 
  25 #include "precompiled.hpp"
  26 #include "code/vmreg.inline.hpp"
  27 #include "compiler/oopMap.hpp"
  28 #include "opto/addnode.hpp"
  29 #include "opto/callnode.hpp"
  30 #include "opto/compile.hpp"
  31 #include "opto/machnode.hpp"
  32 #include "opto/matcher.hpp"
  33 #include "opto/phase.hpp"
  34 #include "opto/regalloc.hpp"
  35 #include "opto/rootnode.hpp"
  36 
  37 // The functions in this file builds OopMaps after all scheduling is done.
  38 //
  39 // OopMaps contain a list of all registers and stack-slots containing oops (so
  40 // they can be updated by GC).  OopMaps also contain a list of derived-pointer
  41 // base-pointer pairs.  When the base is moved, the derived pointer moves to
  42 // follow it.  Finally, any registers holding callee-save values are also
  43 // recorded.  These might contain oops, but only the caller knows.
  44 //
  45 // BuildOopMaps implements a simple forward reaching-defs solution.  At each
  46 // GC point we'll have the reaching-def Nodes.  If the reaching Nodes are
  47 // typed as pointers (no offset), then they are oops.  Pointers+offsets are
  48 // derived pointers, and bases can be found from them.  Finally, we'll also
  49 // track reaching callee-save values.  Note that a copy of a callee-save value
  50 // "kills" it's source, so that only 1 copy of a callee-save value is alive at
  51 // a time.
  52 //
  53 // We run a simple bitvector liveness pass to help trim out dead oops.  Due to
  54 // irreducible loops, we can have a reaching def of an oop that only reaches
  55 // along one path and no way to know if it's valid or not on the other path.
  56 // The bitvectors are quite dense and the liveness pass is fast.
  57 //
  58 // At GC points, we consult this information to build OopMaps.  All reaching
  59 // defs typed as oops are added to the OopMap.  Only 1 instance of a
  60 // callee-save register can be recorded.  For derived pointers, we'll have to
  61 // find and record the register holding the base.
  62 //
  63 // The reaching def's is a simple 1-pass worklist approach.  I tried a clever
  64 // breadth-first approach but it was worse (showed O(n^2) in the
  65 // pick-next-block code).
  66 //
  67 // The relevant data is kept in a struct of arrays (it could just as well be
  68 // an array of structs, but the struct-of-arrays is generally a little more
  69 // efficient).  The arrays are indexed by register number (including
  70 // stack-slots as registers) and so is bounded by 200 to 300 elements in
  71 // practice.  One array will map to a reaching def Node (or NULL for
  72 // conflict/dead).  The other array will map to a callee-saved register or
  73 // OptoReg::Bad for not-callee-saved.
  74 
  75 
  76 // Structure to pass around
  77 struct OopFlow : public ResourceObj {
  78   short *_callees;              // Array mapping register to callee-saved
  79   Node **_defs;                 // array mapping register to reaching def
  80                                 // or NULL if dead/conflict
  81   // OopFlow structs, when not being actively modified, describe the _end_ of
  82   // this block.
  83   Block *_b;                    // Block for this struct
  84   OopFlow *_next;               // Next free OopFlow
  85                                 // or NULL if dead/conflict
  86   Compile* C;
  87 
  88   OopFlow( short *callees, Node **defs, Compile* c ) : _callees(callees), _defs(defs),
  89     _b(NULL), _next(NULL), C(c) { }
  90 
  91   // Given reaching-defs for this block start, compute it for this block end
  92   void compute_reach( PhaseRegAlloc *regalloc, int max_reg, Dict *safehash );
  93 
  94   // Merge these two OopFlows into the 'this' pointer.
  95   void merge( OopFlow *flow, int max_reg );
  96 
  97   // Copy a 'flow' over an existing flow
  98   void clone( OopFlow *flow, int max_size);
  99 
 100   // Make a new OopFlow from scratch
 101   static OopFlow *make( Arena *A, int max_size, Compile* C );
 102 
 103   // Build an oopmap from the current flow info
 104   OopMap *build_oop_map( Node *n, int max_reg, PhaseRegAlloc *regalloc, int* live );
 105 };
 106 
 107 // Given reaching-defs for this block start, compute it for this block end
 108 void OopFlow::compute_reach( PhaseRegAlloc *regalloc, int max_reg, Dict *safehash ) {
 109 
 110   for( uint i=0; i<_b->number_of_nodes(); i++ ) {
 111     Node *n = _b->get_node(i);
 112 
 113     if( n->jvms() ) {           // Build an OopMap here?
 114       JVMState *jvms = n->jvms();
 115       // no map needed for leaf calls
 116       if( n->is_MachSafePoint() && !n->is_MachCallLeaf() ) {
 117         int *live = (int*) (*safehash)[n];
 118         assert( live, "must find live" );
 119         n->as_MachSafePoint()->set_oop_map( build_oop_map(n,max_reg,regalloc, live) );
 120       }
 121     }
 122 
 123     // Assign new reaching def's.
 124     // Note that I padded the _defs and _callees arrays so it's legal
 125     // to index at _defs[OptoReg::Bad].
 126     OptoReg::Name first = regalloc->get_reg_first(n);
 127     OptoReg::Name second = regalloc->get_reg_second(n);
 128     _defs[first] = n;
 129     _defs[second] = n;
 130 
 131     // Pass callee-save info around copies
 132     int idx = n->is_Copy();
 133     if( idx ) {                 // Copies move callee-save info
 134       OptoReg::Name old_first = regalloc->get_reg_first(n->in(idx));
 135       OptoReg::Name old_second = regalloc->get_reg_second(n->in(idx));
 136       int tmp_first = _callees[old_first];
 137       int tmp_second = _callees[old_second];
 138       _callees[old_first] = OptoReg::Bad; // callee-save is moved, dead in old location
 139       _callees[old_second] = OptoReg::Bad;
 140       _callees[first] = tmp_first;
 141       _callees[second] = tmp_second;
 142     } else if( n->is_Phi() ) {  // Phis do not mod callee-saves
 143       assert( _callees[first] == _callees[regalloc->get_reg_first(n->in(1))], "" );
 144       assert( _callees[second] == _callees[regalloc->get_reg_second(n->in(1))], "" );
 145       assert( _callees[first] == _callees[regalloc->get_reg_first(n->in(n->req()-1))], "" );
 146       assert( _callees[second] == _callees[regalloc->get_reg_second(n->in(n->req()-1))], "" );
 147     } else {
 148       _callees[first] = OptoReg::Bad; // No longer holding a callee-save value
 149       _callees[second] = OptoReg::Bad;
 150 
 151       // Find base case for callee saves
 152       if( n->is_Proj() && n->in(0)->is_Start() ) {
 153         if( OptoReg::is_reg(first) &&
 154             regalloc->_matcher.is_save_on_entry(first) )
 155           _callees[first] = first;
 156         if( OptoReg::is_reg(second) &&
 157             regalloc->_matcher.is_save_on_entry(second) )
 158           _callees[second] = second;
 159       }
 160     }
 161   }
 162 }
 163 
 164 // Merge the given flow into the 'this' flow
 165 void OopFlow::merge( OopFlow *flow, int max_reg ) {
 166   assert( _b == NULL, "merging into a happy flow" );
 167   assert( flow->_b, "this flow is still alive" );
 168   assert( flow != this, "no self flow" );
 169 
 170   // Do the merge.  If there are any differences, drop to 'bottom' which
 171   // is OptoReg::Bad or NULL depending.
 172   for( int i=0; i<max_reg; i++ ) {
 173     // Merge the callee-save's
 174     if( _callees[i] != flow->_callees[i] )
 175       _callees[i] = OptoReg::Bad;
 176     // Merge the reaching defs
 177     if( _defs[i] != flow->_defs[i] )
 178       _defs[i] = NULL;
 179   }
 180 
 181 }
 182 
 183 void OopFlow::clone( OopFlow *flow, int max_size ) {
 184   _b = flow->_b;
 185   memcpy( _callees, flow->_callees, sizeof(short)*max_size);
 186   memcpy( _defs   , flow->_defs   , sizeof(Node*)*max_size);
 187 }
 188 
 189 OopFlow *OopFlow::make( Arena *A, int max_size, Compile* C ) {
 190   short *callees = NEW_ARENA_ARRAY(A,short,max_size+1);
 191   Node **defs    = NEW_ARENA_ARRAY(A,Node*,max_size+1);
 192   debug_only( memset(defs,0,(max_size+1)*sizeof(Node*)) );
 193   OopFlow *flow = new (A) OopFlow(callees+1, defs+1, C);
 194   assert( &flow->_callees[OptoReg::Bad] == callees, "Ok to index at OptoReg::Bad" );
 195   assert( &flow->_defs   [OptoReg::Bad] == defs   , "Ok to index at OptoReg::Bad" );
 196   return flow;
 197 }
 198 
 199 static int get_live_bit( int *live, int reg ) {
 200   return live[reg>>LogBitsPerInt] &   (1<<(reg&(BitsPerInt-1))); }
 201 static void set_live_bit( int *live, int reg ) {
 202          live[reg>>LogBitsPerInt] |=  (1<<(reg&(BitsPerInt-1))); }
 203 static void clr_live_bit( int *live, int reg ) {
 204          live[reg>>LogBitsPerInt] &= ~(1<<(reg&(BitsPerInt-1))); }
 205 
 206 // Build an oopmap from the current flow info
 207 OopMap *OopFlow::build_oop_map( Node *n, int max_reg, PhaseRegAlloc *regalloc, int* live ) {
 208   int framesize = regalloc->_framesize;
 209   int max_inarg_slot = OptoReg::reg2stack(regalloc->_matcher._new_SP);
 210   debug_only( char *dup_check = NEW_RESOURCE_ARRAY(char,OptoReg::stack0());
 211               memset(dup_check,0,OptoReg::stack0()) );
 212 
 213   OopMap *omap = new OopMap( framesize,  max_inarg_slot );
 214   MachCallNode *mcall = n->is_MachCall() ? n->as_MachCall() : NULL;
 215   JVMState* jvms = n->jvms();
 216 
 217   // For all registers do...
 218   for( int reg=0; reg<max_reg; reg++ ) {
 219     if( get_live_bit(live,reg) == 0 )
 220       continue;                 // Ignore if not live
 221 
 222     // %%% C2 can use 2 OptoRegs when the physical register is only one 64bit
 223     // register in that case we'll get an non-concrete register for the second
 224     // half. We only need to tell the map the register once!
 225     //
 226     // However for the moment we disable this change and leave things as they
 227     // were.
 228 
 229     VMReg r = OptoReg::as_VMReg(OptoReg::Name(reg), framesize, max_inarg_slot);
 230 
 231     if (false && r->is_reg() && !r->is_concrete()) {
 232       continue;
 233     }
 234 
 235     // See if dead (no reaching def).
 236     Node *def = _defs[reg];     // Get reaching def
 237     assert( def, "since live better have reaching def" );
 238 
 239     // Classify the reaching def as oop, derived, callee-save, dead, or other
 240     const Type *t = def->bottom_type();
 241     if( t->isa_oop_ptr() ) {    // Oop or derived?
 242       assert( !OptoReg::is_valid(_callees[reg]), "oop can't be callee save" );
 243 #ifdef _LP64
 244       // 64-bit pointers record oop-ishness on 2 aligned adjacent registers.
 245       // Make sure both are record from the same reaching def, but do not
 246       // put both into the oopmap.
 247       if( (reg&1) == 1 ) {      // High half of oop-pair?
 248         assert( _defs[reg-1] == _defs[reg], "both halves from same reaching def" );
 249         continue;               // Do not record high parts in oopmap
 250       }
 251 #endif
 252 
 253       // Check for a legal reg name in the oopMap and bailout if it is not.
 254       if (!omap->legal_vm_reg_name(r)) {
 255         regalloc->C->record_method_not_compilable("illegal oopMap register name");
 256         continue;
 257       }
 258       if( t->is_ptr()->_offset == 0 ) { // Not derived?
 259         if( mcall ) {
 260           // Outgoing argument GC mask responsibility belongs to the callee,
 261           // not the caller.  Inspect the inputs to the call, to see if
 262           // this live-range is one of them.
 263           uint cnt = mcall->tf()->domain()->cnt();
 264           uint j;
 265           for( j = TypeFunc::Parms; j < cnt; j++)
 266             if( mcall->in(j) == def )
 267               break;            // reaching def is an argument oop
 268           if( j < cnt )         // arg oops dont go in GC map
 269             continue;           // Continue on to the next register
 270         }
 271         omap->set_oop(r);
 272       } else {                  // Else it's derived.
 273         // Find the base of the derived value.
 274         uint i;
 275         // Fast, common case, scan
 276         for( i = jvms->oopoff(); i < n->req(); i+=2 )
 277           if( n->in(i) == def ) break; // Common case
 278         if( i == n->req() ) {   // Missed, try a more generous scan
 279           // Scan again, but this time peek through copies
 280           for( i = jvms->oopoff(); i < n->req(); i+=2 ) {
 281             Node *m = n->in(i); // Get initial derived value
 282             while( 1 ) {
 283               Node *d = def;    // Get initial reaching def
 284               while( 1 ) {      // Follow copies of reaching def to end
 285                 if( m == d ) goto found; // breaks 3 loops
 286                 int idx = d->is_Copy();
 287                 if( !idx ) break;
 288                 d = d->in(idx);     // Link through copy
 289               }
 290               int idx = m->is_Copy();
 291               if( !idx ) break;
 292               m = m->in(idx);
 293             }
 294           }
 295           guarantee( 0, "must find derived/base pair" );
 296         }
 297       found: ;
 298         Node *base = n->in(i+1); // Base is other half of pair
 299         int breg = regalloc->get_reg_first(base);
 300         VMReg b = OptoReg::as_VMReg(OptoReg::Name(breg), framesize, max_inarg_slot);
 301 
 302         // I record liveness at safepoints BEFORE I make the inputs
 303         // live.  This is because argument oops are NOT live at a
 304         // safepoint (or at least they cannot appear in the oopmap).
 305         // Thus bases of base/derived pairs might not be in the
 306         // liveness data but they need to appear in the oopmap.
 307         if( get_live_bit(live,breg) == 0 ) {// Not live?
 308           // Flag it, so next derived pointer won't re-insert into oopmap
 309           set_live_bit(live,breg);
 310           // Already missed our turn?
 311           if( breg < reg ) {
 312             if (b->is_stack() || b->is_concrete() || true ) {
 313               omap->set_oop( b);
 314             }
 315           }
 316         }
 317         if (b->is_stack() || b->is_concrete() || true ) {
 318           omap->set_derived_oop( r, b);
 319         }
 320       }
 321 
 322     } else if( t->isa_narrowoop() ) {
 323       assert( !OptoReg::is_valid(_callees[reg]), "oop can't be callee save" );
 324       // Check for a legal reg name in the oopMap and bailout if it is not.
 325       if (!omap->legal_vm_reg_name(r)) {
 326         regalloc->C->record_method_not_compilable("illegal oopMap register name");
 327         continue;
 328       }
 329       if( mcall ) {
 330           // Outgoing argument GC mask responsibility belongs to the callee,
 331           // not the caller.  Inspect the inputs to the call, to see if
 332           // this live-range is one of them.
 333         uint cnt = mcall->tf()->domain()->cnt();
 334         uint j;
 335         for( j = TypeFunc::Parms; j < cnt; j++)
 336           if( mcall->in(j) == def )
 337             break;            // reaching def is an argument oop
 338         if( j < cnt )         // arg oops dont go in GC map
 339           continue;           // Continue on to the next register
 340       }
 341       omap->set_narrowoop(r);
 342     } else if( OptoReg::is_valid(_callees[reg])) { // callee-save?
 343       // It's a callee-save value
 344       assert( dup_check[_callees[reg]]==0, "trying to callee save same reg twice" );
 345       debug_only( dup_check[_callees[reg]]=1; )
 346       VMReg callee = OptoReg::as_VMReg(OptoReg::Name(_callees[reg]));
 347       if ( callee->is_concrete() || true ) {
 348         omap->set_callee_saved( r, callee);
 349       }
 350 
 351     } else {
 352       // Other - some reaching non-oop value
 353       omap->set_value( r);
 354 #ifdef ASSERT
 355       if( t->isa_rawptr() && C->cfg()->_raw_oops.member(def) ) {
 356         def->dump();
 357         n->dump();
 358         assert(false, "there should be a oop in OopMap instead of a live raw oop at safepoint");
 359       }
 360 #endif
 361     }
 362 
 363   }
 364 
 365 #ifdef ASSERT
 366   /* Nice, Intel-only assert
 367   int cnt_callee_saves=0;
 368   int reg2 = 0;
 369   while (OptoReg::is_reg(reg2)) {
 370     if( dup_check[reg2] != 0) cnt_callee_saves++;
 371     assert( cnt_callee_saves==3 || cnt_callee_saves==5, "missed some callee-save" );
 372     reg2++;
 373   }
 374   */
 375 #endif
 376 
 377 #ifdef ASSERT
 378   for( OopMapStream oms1(omap, OopMapValue::derived_oop_value); !oms1.is_done(); oms1.next()) {
 379     OopMapValue omv1 = oms1.current();
 380     bool found = false;
 381     for( OopMapStream oms2(omap,OopMapValue::oop_value); !oms2.is_done(); oms2.next()) {
 382       if( omv1.content_reg() == oms2.current().reg() ) {
 383         found = true;
 384         break;
 385       }
 386     }
 387     assert( found, "derived with no base in oopmap" );
 388   }
 389 #endif
 390 
 391   return omap;
 392 }
 393 
 394 // Compute backwards liveness on registers
 395 static void do_liveness(PhaseRegAlloc* regalloc, PhaseCFG* cfg, Block_List* worklist, int max_reg_ints, Arena* A, Dict* safehash) {
 396   int* live = NEW_ARENA_ARRAY(A, int, (cfg->number_of_blocks() + 1) * max_reg_ints);
 397   int* tmp_live = &live[cfg->number_of_blocks() * max_reg_ints];
 398   Node* root = cfg->get_root_node();
 399   // On CISC platforms, get the node representing the stack pointer  that regalloc
 400   // used for spills
 401   Node *fp = NodeSentinel;
 402   if (UseCISCSpill && root->req() > 1) {
 403     fp = root->in(1)->in(TypeFunc::FramePtr);
 404   }
 405   memset(live, 0, cfg->number_of_blocks() * (max_reg_ints << LogBytesPerInt));
 406   // Push preds onto worklist
 407   for (uint i = 1; i < root->req(); i++) {
 408     Block* block = cfg->get_block_for_node(root->in(i));
 409     worklist->push(block);
 410   }
 411 
 412   // ZKM.jar includes tiny infinite loops which are unreached from below.
 413   // If we missed any blocks, we'll retry here after pushing all missed
 414   // blocks on the worklist.  Normally this outer loop never trips more
 415   // than once.
 416   while (1) {
 417 
 418     while( worklist->size() ) { // Standard worklist algorithm
 419       Block *b = worklist->rpop();
 420 
 421       // Copy first successor into my tmp_live space
 422       int s0num = b->_succs[0]->_pre_order;
 423       int *t = &live[s0num*max_reg_ints];
 424       for( int i=0; i<max_reg_ints; i++ )
 425         tmp_live[i] = t[i];
 426 
 427       // OR in the remaining live registers
 428       for( uint j=1; j<b->_num_succs; j++ ) {
 429         uint sjnum = b->_succs[j]->_pre_order;
 430         int *t = &live[sjnum*max_reg_ints];
 431         for( int i=0; i<max_reg_ints; i++ )
 432           tmp_live[i] |= t[i];
 433       }
 434 
 435       // Now walk tmp_live up the block backwards, computing live
 436       for( int k=b->number_of_nodes()-1; k>=0; k-- ) {
 437         Node *n = b->get_node(k);
 438         // KILL def'd bits
 439         int first = regalloc->get_reg_first(n);
 440         int second = regalloc->get_reg_second(n);
 441         if( OptoReg::is_valid(first) ) clr_live_bit(tmp_live,first);
 442         if( OptoReg::is_valid(second) ) clr_live_bit(tmp_live,second);
 443 
 444         MachNode *m = n->is_Mach() ? n->as_Mach() : NULL;
 445 
 446         // Check if m is potentially a CISC alternate instruction (i.e, possibly
 447         // synthesized by RegAlloc from a conventional instruction and a
 448         // spilled input)
 449         bool is_cisc_alternate = false;
 450         if (UseCISCSpill && m) {
 451           is_cisc_alternate = m->is_cisc_alternate();
 452         }
 453 
 454         // GEN use'd bits
 455         for( uint l=1; l<n->req(); l++ ) {
 456           Node *def = n->in(l);
 457           assert(def != 0, "input edge required");
 458           int first = regalloc->get_reg_first(def);
 459           int second = regalloc->get_reg_second(def);
 460           if( OptoReg::is_valid(first) ) set_live_bit(tmp_live,first);
 461           if( OptoReg::is_valid(second) ) set_live_bit(tmp_live,second);
 462           // If we use the stack pointer in a cisc-alternative instruction,
 463           // check for use as a memory operand.  Then reconstruct the RegName
 464           // for this stack location, and set the appropriate bit in the
 465           // live vector 4987749.
 466           if (is_cisc_alternate && def == fp) {
 467             const TypePtr *adr_type = NULL;
 468             intptr_t offset;
 469             const Node* base = m->get_base_and_disp(offset, adr_type);
 470             if (base == NodeSentinel) {
 471               // Machnode has multiple memory inputs. We are unable to reason
 472               // with these, but are presuming (with trepidation) that not any of
 473               // them are oops. This can be fixed by making get_base_and_disp()
 474               // look at a specific input instead of all inputs.
 475               assert(!def->bottom_type()->isa_oop_ptr(), "expecting non-oop mem input");
 476             } else if (base != fp || offset == Type::OffsetBot) {
 477               // Do nothing: the fp operand is either not from a memory use
 478               // (base == NULL) OR the fp is used in a non-memory context
 479               // (base is some other register) OR the offset is not constant,
 480               // so it is not a stack slot.
 481             } else {
 482               assert(offset >= 0, "unexpected negative offset");
 483               offset -= (offset % jintSize);  // count the whole word
 484               int stack_reg = regalloc->offset2reg(offset);
 485               if (OptoReg::is_stack(stack_reg)) {
 486                 set_live_bit(tmp_live, stack_reg);
 487               } else {
 488                 assert(false, "stack_reg not on stack?");
 489               }
 490             }
 491           }
 492         }
 493 
 494         if( n->jvms() ) {       // Record liveness at safepoint
 495 
 496           // This placement of this stanza means inputs to calls are
 497           // considered live at the callsite's OopMap.  Argument oops are
 498           // hence live, but NOT included in the oopmap.  See cutout in
 499           // build_oop_map.  Debug oops are live (and in OopMap).
 500           int *n_live = NEW_ARENA_ARRAY(A, int, max_reg_ints);
 501           for( int l=0; l<max_reg_ints; l++ )
 502             n_live[l] = tmp_live[l];
 503           safehash->Insert(n,n_live);
 504         }
 505 
 506       }
 507 
 508       // Now at block top, see if we have any changes.  If so, propagate
 509       // to prior blocks.
 510       int *old_live = &live[b->_pre_order*max_reg_ints];
 511       int l;
 512       for( l=0; l<max_reg_ints; l++ )
 513         if( tmp_live[l] != old_live[l] )
 514           break;
 515       if( l<max_reg_ints ) {     // Change!
 516         // Copy in new value
 517         for( l=0; l<max_reg_ints; l++ )
 518           old_live[l] = tmp_live[l];
 519         // Push preds onto worklist
 520         for (l = 1; l < (int)b->num_preds(); l++) {
 521           Block* block = cfg->get_block_for_node(b->pred(l));
 522           worklist->push(block);
 523         }
 524       }
 525     }
 526 
 527     // Scan for any missing safepoints.  Happens to infinite loops
 528     // ala ZKM.jar
 529     uint i;
 530     for (i = 1; i < cfg->number_of_blocks(); i++) {
 531       Block* block = cfg->get_block(i);
 532       uint j;
 533       for (j = 1; j < block->number_of_nodes(); j++) {
 534         if (block->get_node(j)->jvms() && (*safehash)[block->get_node(j)] == NULL) {
 535            break;
 536         }
 537       }
 538       if (j < block->number_of_nodes()) {
 539         break;
 540       }
 541     }
 542     if (i == cfg->number_of_blocks()) {
 543       break;                    // Got 'em all
 544     }
 545 
 546     if (PrintOpto && Verbose) {
 547       tty->print_cr("retripping live calc");
 548     }
 549 
 550     // Force the issue (expensively): recheck everybody
 551     for (i = 1; i < cfg->number_of_blocks(); i++) {
 552       worklist->push(cfg->get_block(i));
 553     }
 554   }
 555 }
 556 
 557 // Collect GC mask info - where are all the OOPs?
 558 void Compile::BuildOopMaps() {
 559   TracePhase tp("bldOopMaps", &timers[_t_buildOopMaps]);
 560   // Can't resource-mark because I need to leave all those OopMaps around,
 561   // or else I need to resource-mark some arena other than the default.
 562   // ResourceMark rm;              // Reclaim all OopFlows when done
 563   int max_reg = _regalloc->_max_reg; // Current array extent
 564 
 565   Arena *A = Thread::current()->resource_area();
 566   Block_List worklist;          // Worklist of pending blocks
 567 
 568   int max_reg_ints = round_to(max_reg, BitsPerInt)>>LogBitsPerInt;
 569   Dict *safehash = NULL;        // Used for assert only
 570   // Compute a backwards liveness per register.  Needs a bitarray of
 571   // #blocks x (#registers, rounded up to ints)
 572   safehash = new Dict(cmpkey,hashkey,A);
 573   do_liveness( _regalloc, _cfg, &worklist, max_reg_ints, A, safehash );
 574   OopFlow *free_list = NULL;    // Free, unused
 575 
 576   // Array mapping blocks to completed oopflows
 577   OopFlow **flows = NEW_ARENA_ARRAY(A, OopFlow*, _cfg->number_of_blocks());
 578   memset( flows, 0, _cfg->number_of_blocks() * sizeof(OopFlow*) );
 579 
 580 
 581   // Do the first block 'by hand' to prime the worklist
 582   Block *entry = _cfg->get_block(1);
 583   OopFlow *rootflow = OopFlow::make(A,max_reg,this);
 584   // Initialize to 'bottom' (not 'top')
 585   memset( rootflow->_callees, OptoReg::Bad, max_reg*sizeof(short) );
 586   memset( rootflow->_defs   ,            0, max_reg*sizeof(Node*) );
 587   flows[entry->_pre_order] = rootflow;
 588 
 589   // Do the first block 'by hand' to prime the worklist
 590   rootflow->_b = entry;
 591   rootflow->compute_reach( _regalloc, max_reg, safehash );
 592   for( uint i=0; i<entry->_num_succs; i++ )
 593     worklist.push(entry->_succs[i]);
 594 
 595   // Now worklist contains blocks which have some, but perhaps not all,
 596   // predecessors visited.
 597   while( worklist.size() ) {
 598     // Scan for a block with all predecessors visited, or any randoms slob
 599     // otherwise.  All-preds-visited order allows me to recycle OopFlow
 600     // structures rapidly and cut down on the memory footprint.
 601     // Note: not all predecessors might be visited yet (must happen for
 602     // irreducible loops).  This is OK, since every live value must have the
 603     // SAME reaching def for the block, so any reaching def is OK.
 604     uint i;
 605 
 606     Block *b = worklist.pop();
 607     // Ignore root block
 608     if (b == _cfg->get_root_block()) {
 609       continue;
 610     }
 611     // Block is already done?  Happens if block has several predecessors,
 612     // he can get on the worklist more than once.
 613     if( flows[b->_pre_order] ) continue;
 614 
 615     // If this block has a visited predecessor AND that predecessor has this
 616     // last block as his only undone child, we can move the OopFlow from the
 617     // pred to this block.  Otherwise we have to grab a new OopFlow.
 618     OopFlow *flow = NULL;       // Flag for finding optimized flow
 619     Block *pred = (Block*)0xdeadbeef;
 620     // Scan this block's preds to find a done predecessor
 621     for (uint j = 1; j < b->num_preds(); j++) {
 622       Block* p = _cfg->get_block_for_node(b->pred(j));
 623       OopFlow *p_flow = flows[p->_pre_order];
 624       if( p_flow ) {            // Predecessor is done
 625         assert( p_flow->_b == p, "cross check" );
 626         pred = p;               // Record some predecessor
 627         // If all successors of p are done except for 'b', then we can carry
 628         // p_flow forward to 'b' without copying, otherwise we have to draw
 629         // from the free_list and clone data.
 630         uint k;
 631         for( k=0; k<p->_num_succs; k++ )
 632           if( !flows[p->_succs[k]->_pre_order] &&
 633               p->_succs[k] != b )
 634             break;
 635 
 636         // Either carry-forward the now-unused OopFlow for b's use
 637         // or draw a new one from the free list
 638         if( k==p->_num_succs ) {
 639           flow = p_flow;
 640           break;                // Found an ideal pred, use him
 641         }
 642       }
 643     }
 644 
 645     if( flow ) {
 646       // We have an OopFlow that's the last-use of a predecessor.
 647       // Carry it forward.
 648     } else {                    // Draw a new OopFlow from the freelist
 649       if( !free_list )
 650         free_list = OopFlow::make(A,max_reg,C);
 651       flow = free_list;
 652       assert( flow->_b == NULL, "oopFlow is not free" );
 653       free_list = flow->_next;
 654       flow->_next = NULL;
 655 
 656       // Copy/clone over the data
 657       flow->clone(flows[pred->_pre_order], max_reg);
 658     }
 659 
 660     // Mark flow for block.  Blocks can only be flowed over once,
 661     // because after the first time they are guarded from entering
 662     // this code again.
 663     assert( flow->_b == pred, "have some prior flow" );
 664     flow->_b = NULL;
 665 
 666     // Now push flow forward
 667     flows[b->_pre_order] = flow;// Mark flow for this block
 668     flow->_b = b;
 669     flow->compute_reach( _regalloc, max_reg, safehash );
 670 
 671     // Now push children onto worklist
 672     for( i=0; i<b->_num_succs; i++ )
 673       worklist.push(b->_succs[i]);
 674 
 675   }
 676 }
--- EOF ---