ART: Use C++17 extract/modify/insert pattern.

Test: m test-art-host-gtest
Test: testrunner.py --host --optimizing
Bug: 123750182
Change-Id: I2721948a566cc11d351324d173b4e1c8e5e54f53

2 files changed, 11 insertions, 27 deletions

diff --git a/compiler/utils/swap_space.cc b/compiler/utils/swap_space.cc
index dee83d1c71..841ff1c58d 100644
--- a/compiler/utils/swap_space.cc
+++ b/compiler/utils/swap_space.cc
@@ -115,12 +115,11 @@ void* SwapSpace::Alloc(size_t size) {
       ? free_by_size_.end()
       : free_by_size_.lower_bound(FreeBySizeEntry { size, free_by_start_.begin() });
   if (it != free_by_size_.end()) {
-    auto entry = it->free_by_start_entry;
-    SpaceChunk old_chunk = *entry;
+    SpaceChunk old_chunk = *it->free_by_start_entry;
     if (old_chunk.size == size) {
       RemoveChunk(it);
     } else {
-      // Try to avoid deallocating and allocating the std::set<> nodes.
+      // Avoid deallocating and allocating the std::set<> nodes.
       // This would be much simpler if we could use replace() from Boost.Bimap.
 
       // The free_by_start_ map contains disjoint intervals ordered by the `ptr`.
@@ -128,24 +127,9 @@ void* SwapSpace::Alloc(size_t size) {
       it->free_by_start_entry->ptr += size;
       it->free_by_start_entry->size -= size;
 
-      // The free_by_size_ map is ordered by the `size` and then `free_by_start_entry->ptr`.
-      // Adjusting the `ptr` above does not change that ordering but decreasing `size` can
-      // push the node before the previous node(s).
-      if (it == free_by_size_.begin()) {
-        it->size -= size;
-      } else {
-        auto prev = it;
-        --prev;
-        FreeBySizeEntry new_value(old_chunk.size - size, entry);
-        if (free_by_size_.key_comp()(*prev, new_value)) {
-          it->size -= size;
-        } else {
-          // Changing in place would break the std::set<> ordering, we need to remove and insert.
-          // TODO: When C++17 becomes available, use std::map<>::extract(), modify, insert.
-          free_by_size_.erase(it);
-          free_by_size_.insert(new_value);
-        }
-      }
+      auto node = free_by_size_.extract(it);
+      node.value().size -= size;
+      free_by_size_.insert(std::move(node));
     }
     return old_chunk.ptr;
   } else {
diff --git a/libartbase/base/mem_map.cc b/libartbase/base/mem_map.cc
index 28337507d8..ba2a7c6b93 100644
--- a/libartbase/base/mem_map.cc
+++ b/libartbase/base/mem_map.cc
@@ -796,13 +796,13 @@ void MemMap::ReleaseReservedMemory(size_t byte_count) {
     // Shrink the reservation MemMap and update its `gMaps` entry.
     std::lock_guard<std::mutex> mu(*mem_maps_lock_);
     auto it = GetGMapsEntry(*this);
-    // TODO: When C++17 becomes available, use std::map<>::extract(), modify, insert.
-    gMaps->erase(it);
+    auto node = gMaps->extract(it);
     begin_ += byte_count;
     size_ -= byte_count;
     base_begin_ = begin_;
     base_size_ = size_;
-    gMaps->emplace(base_begin_, this);
+    node.key() = base_begin_;
+    gMaps->insert(std::move(node));
   }
 }
 
@@ -1266,9 +1266,9 @@ void MemMap::AlignBy(size_t size) {
   std::lock_guard<std::mutex> mu(*mem_maps_lock_);
   if (base_begin < aligned_base_begin) {
     auto it = GetGMapsEntry(*this);
-    // TODO: When C++17 becomes available, use std::map<>::extract(), modify, insert.
-    gMaps->erase(it);
-    gMaps->insert(std::make_pair(aligned_base_begin, this));
+    auto node = gMaps->extract(it);
+    node.key() = aligned_base_begin;
+    gMaps->insert(std::move(node));
   }
   base_begin_ = aligned_base_begin;
   base_size_ = aligned_base_size;