8236073: G1: Use SoftMaxHeapSize to guide GC heuristics

*** 156,173 ****
    }
    if (cur == end_idx + 1) {
      return num_regions;
    }
    *res_idx = cur;
!   while (cur <= end_idx && !is_available(cur)) {
      cur++;
    }
    num_regions = cur - *res_idx;
  
  #ifdef ASSERT
    for (uint i = *res_idx; i < (*res_idx + num_regions); i++) {
!     assert(!is_available(i), "just checking");
    }
    assert(cur == end_idx + 1 || num_regions == 0 || is_available(cur),
      "The region at the current position %u must be available or at the end", cur);
  #endif
    return num_regions;
--- 156,173 ----
    }
    if (cur == end_idx + 1) {
      return num_regions;
    }
    *res_idx = cur;
!   while (cur <= end_idx && is_unavailable_for_allocation(cur)) {
      cur++;
    }
    num_regions = cur - *res_idx;
  
  #ifdef ASSERT
    for (uint i = *res_idx; i < (*res_idx + num_regions); i++) {
!     assert(is_unavailable_for_allocation(i), "just checking");
    }
    assert(cur == end_idx + 1 || num_regions == 0 || is_available(cur),
      "The region at the current position %u must be available or at the end", cur);
  #endif
    return num_regions;
*** 345,357 ****
    uint cur = (uint)start;
    uint length_unavailable = 0;
  
    while (length_found < num && cur <= end) {
      HeapRegion* hr = _regions.get_by_index(cur);
!     if ((!empty_only && !is_available(cur)) || (is_available(cur) && hr != NULL && hr->is_empty())) {
        // This region is a potential candidate for allocation into.
!       if (!is_available(cur)) {
          if(shrink_dram(1) == 1) {
            uint ret = expand_in_range(cur, cur, 1, NULL);
            assert(ret == 1, "We should be able to expand at this index");
          } else {
            length_unavailable++;
--- 345,357 ----
    uint cur = (uint)start;
    uint length_unavailable = 0;
  
    while (length_found < num && cur <= end) {
      HeapRegion* hr = _regions.get_by_index(cur);
!     if ((!empty_only && is_unavailable_for_allocation(cur)) || (is_available(cur) && hr != NULL && hr->is_empty())) {
        // This region is a potential candidate for allocation into.
!       if (is_unavailable_for_allocation(cur)) {
          if(shrink_dram(1) == 1) {
            uint ret = expand_in_range(cur, cur, 1, NULL);
            assert(ret == 1, "We should be able to expand at this index");
          } else {
            length_unavailable++;
*** 369,379 ****
  
    if (length_found == num) {
      for (uint i = found; i < (found + num); i++) {
        HeapRegion* hr = _regions.get_by_index(i);
        // sanity check
!       guarantee((!empty_only && !is_available(i)) || (is_available(i) && hr != NULL && hr->is_empty()),
                  "Found region sequence starting at " UINT32_FORMAT ", length " SIZE_FORMAT
                  " that is not empty at " UINT32_FORMAT ". Hr is " PTR_FORMAT, found, num, i, p2i(hr));
      }
      if (!empty_only && length_unavailable > (max_expandable_length() - total_regions_committed())) {
        // if 'length_unavailable' number of regions will be made available, we will exceed max regions.
--- 369,379 ----
  
    if (length_found == num) {
      for (uint i = found; i < (found + num); i++) {
        HeapRegion* hr = _regions.get_by_index(i);
        // sanity check
!       guarantee((!empty_only && is_unavailable_for_allocation(i)) || (is_available(i) && hr != NULL && hr->is_empty()),
                  "Found region sequence starting at " UINT32_FORMAT ", length " SIZE_FORMAT
                  " that is not empty at " UINT32_FORMAT ". Hr is " PTR_FORMAT, found, num, i, p2i(hr));
      }
      if (!empty_only && length_unavailable > (max_expandable_length() - total_regions_committed())) {
        // if 'length_unavailable' number of regions will be made available, we will exceed max regions.