src/share/vm/opto/gcm.cpp

*** 27,36 ****
--- 27,39 ----
  // Optimization - Graph Style
  
  #include "incls/_precompiled.incl"
  #include "incls/_gcm.cpp.incl"
  
+ // To avoid float value underflow
+ #define MIN_BLOCK_FREQUENCY 1.e-35f
+ 
  //----------------------------schedule_node_into_block-------------------------
  // Insert node n into block b. Look for projections of n and make sure they
  // are in b also.
  void PhaseCFG::schedule_node_into_block( Node *n, Block *b ) {
    // Set basic block of n, Add n to b,
*** 1378,1387 ****
--- 1381,1397 ----
          }
        }
      }
    }
  
+ #ifdef ASSERT
+   for (uint i = 0; i < _num_blocks; i++ ) {
+     Block *b = _blocks[i];
+     assert(b->_freq >= MIN_BLOCK_FREQUENCY, "Register Allocator requiers meaningful block frequency");
+   }
+ #endif
+ 
  #ifndef PRODUCT
    if (PrintCFGBlockFreq) {
      tty->print_cr("CFG Block Frequencies");
      _root_loop->dump_tree();
      if (Verbose) {
*** 1875,1885 ****
  // Do a top down traversal of loop tree (visit outer loops first.)
  void CFGLoop::scale_freq() {
    float loop_freq = _freq * trip_count();
    for (int i = 0; i < _members.length(); i++) {
      CFGElement* s = _members.at(i);
!     s->_freq *= loop_freq;
    }
    CFGLoop* ch = _child;
    while (ch != NULL) {
      ch->scale_freq();
      ch = ch->_sibling;
--- 1885,1897 ----
  // Do a top down traversal of loop tree (visit outer loops first.)
  void CFGLoop::scale_freq() {
    float loop_freq = _freq * trip_count();
    for (int i = 0; i < _members.length(); i++) {
      CFGElement* s = _members.at(i);
!     float block_freq = s->_freq * loop_freq;
!     if (block_freq < MIN_BLOCK_FREQUENCY) block_freq = MIN_BLOCK_FREQUENCY;
!     s->_freq = block_freq;
    }
    CFGLoop* ch = _child;
    while (ch != NULL) {
      ch->scale_freq();
      ch = ch->_sibling;