/*

 * Copyright (c) 2002, 2016, 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 "code/vmreg.inline.hpp"

#include "compiler/oopMap.hpp"

#include "memory/resourceArea.hpp"

#include "opto/addnode.hpp"

#include "opto/callnode.hpp"

#include "opto/compile.hpp"

#include "opto/machnode.hpp"

#include "opto/matcher.hpp"

#include "opto/phase.hpp"

#include "opto/regalloc.hpp"

#include "opto/rootnode.hpp"

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

//

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

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

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

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

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

//

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

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

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

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

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

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

// a time.

//

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

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

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

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

//

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

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

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

// find and record the register holding the base.

//

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

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

// pick-next-block code).

//

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

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

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

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

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

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

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

// Structure to pass around

struct OopFlow : public ResourceObj {

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

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

                                // or NULL if dead/conflict

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

  // this block.

  Block *_b;                    // Block for this struct

  OopFlow *_next;               // Next free OopFlow

                                // or NULL if dead/conflict

  Compile* C;

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

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

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

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

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

  void merge( OopFlow *flow, int max_reg );

  // Copy a 'flow' over an existing flow

  void clone( OopFlow *flow, int max_size);

  // Make a new OopFlow from scratch

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

  // Build an oopmap from the current flow info

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

};

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

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

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

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

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

      JVMState *jvms = n->jvms();

      // no map needed for leaf calls

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

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

        assert( live, "must find live" );

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

      }

    }

    // Assign new reaching def's.

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

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

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

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

    _defs[first] = n;

    _defs[second] = n;

    // Pass callee-save info around copies

    int idx = n->is_Copy();

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

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

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

      int tmp_first = _callees[old_first];

      int tmp_second = _callees[old_second];

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

      _callees[old_second] = OptoReg::Bad;

      _callees[first] = tmp_first;

      _callees[second] = tmp_second;

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

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

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

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

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

    } else {

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

      _callees[second] = OptoReg::Bad;

      // Find base case for callee saves

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

        if( OptoReg::is_reg(first) &&

            regalloc->_matcher.is_save_on_entry(first) )

          _callees[first] = first;

        if( OptoReg::is_reg(second) &&

            regalloc->_matcher.is_save_on_entry(second) )

          _callees[second] = second;

      }

    }

  }

}

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

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

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

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

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

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

  // is OptoReg::Bad or NULL depending.

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

    // Merge the callee-save's

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

      _callees[i] = OptoReg::Bad;

    // Merge the reaching defs

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

      _defs[i] = NULL;

  }

}

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

  _b = flow->_b;

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

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

}

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

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

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

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

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

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

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

  return flow;

}

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

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

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

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

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

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

// Build an oopmap from the current flow info

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

  int framesize = regalloc->_framesize;

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

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

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

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

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

  JVMState* jvms = n->jvms();

  // For all registers do...

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

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

      continue;                 // Ignore if not live

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

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

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

    //

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

    // were.

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

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

      continue;

    }

    // See if dead (no reaching def).

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

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

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

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

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

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

#ifdef _LP64

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

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

      // put both into the oopmap.

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

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

        continue;               // Do not record high parts in oopmap

      }

#endif

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

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

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

        continue;

      }

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

        if( mcall ) {

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

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

          // this live-range is one of them.

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

          uint j;

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

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

              break;            // reaching def is an argument oop

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

            continue;           // Continue on to the next register

        }

        omap->set_oop(r);

      } else {                  // Else it's derived.

        // Find the base of the derived value.

        uint i;

        // Fast, common case, scan

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

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

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

          // Scan again, but this time peek through copies

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

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

            while( 1 ) {

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

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

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

                int idx = d->is_Copy();

                if( !idx ) break;

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

              }

              int idx = m->is_Copy();

              if( !idx ) break;

              m = m->in(idx);

            }

          }

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

        }

      found: ;

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

        int breg = regalloc->get_reg_first(base);

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

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

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

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

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

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

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

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

          set_live_bit(live,breg);

          // Already missed our turn?

          if( breg < reg ) {

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

              omap->set_oop( b);

            }

          }

        }

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

          omap->set_derived_oop( r, b);

        }

      }

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

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

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

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

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

        continue;

      }

      if( mcall ) {

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

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

          // this live-range is one of them.

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

        uint j;

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

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

            break;            // reaching def is an argument oop

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

          continue;           // Continue on to the next register

      }

      omap->set_narrowoop(r);

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

      // It's a callee-save value

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

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

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

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

        omap->set_callee_saved( r, callee);

      }

    } else {

      // Other - some reaching non-oop value

      omap->set_value( r);

#ifdef ASSERT

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

        def->dump();

        n->dump();

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

      }

#endif

    }

  }

#ifdef ASSERT

  /* Nice, Intel-only assert

  int cnt_callee_saves=0;

  int reg2 = 0;

  while (OptoReg::is_reg(reg2)) {

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

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

    reg2++;

  }

  */

#endif

#ifdef ASSERT

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

    OopMapValue omv1 = oms1.current();

    bool found = false;

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

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

        found = true;

        break;

      }

    }

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

  }

#endif

  return omap;

}

// Compute backwards liveness on registers

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

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

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

  Node* root = cfg->get_root_node();

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

  // used for spills

  Node *fp = NodeSentinel;

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

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

  }

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

  // Push preds onto worklist

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

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

    worklist->push(block);

  }

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

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

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

  // than once.

  while (1) {

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

      Block *b = worklist->rpop();

      // Copy first successor into my tmp_live space

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

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

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

        tmp_live[i] = t[i];

      // OR in the remaining live registers

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

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

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

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

          tmp_live[i] |= t[i];

      }

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

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

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

        // KILL def'd bits

        int first = regalloc->get_reg_first(n);

        int second = regalloc->get_reg_second(n);

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

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

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

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

        // synthesized by RegAlloc from a conventional instruction and a

        // spilled input)

        bool is_cisc_alternate = false;

        if (UseCISCSpill && m) {

          is_cisc_alternate = m->is_cisc_alternate();

        }

        // GEN use'd bits

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

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

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

          int first = regalloc->get_reg_first(def);

          int second = regalloc->get_reg_second(def);

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

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

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

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

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

          // live vector 4987749.

          if (is_cisc_alternate && def == fp) {

            const TypePtr *adr_type = NULL;

            intptr_t offset;

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

            if (base == NodeSentinel) {

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

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

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

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

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

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

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

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

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

              // so it is not a stack slot.

            } else {

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

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

              int stack_reg = regalloc->offset2reg(offset);

              if (OptoReg::is_stack(stack_reg)) {

                set_live_bit(tmp_live, stack_reg);

              } else {

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

              }

            }

          }

        }

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

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

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

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

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

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

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

            n_live[l] = tmp_live[l];

          safehash->Insert(n,n_live);

        }

      }

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

      // to prior blocks.

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

      int l;

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

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

          break;

      if( l<max_reg_ints ) {     // Change!

        // Copy in new value

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

          old_live[l] = tmp_live[l];

        // Push preds onto worklist