[libc++] Refactor some code in monotonic_buffer_resource (llvm#117271)

love1angel · web-flow · commit 6285c46e164b · 2024-12-23T14:32:59.000+08:00
1. remove unused __default_buffer_alignment
2. two __try_allocate_from_chunk are same, put it together

This patch refactor some code in monotonic_buffer_resource.
diff --git a/libcxx/include/__memory_resource/monotonic_buffer_resource.h b/libcxx/include/__memory_resource/monotonic_buffer_resource.h
@@ -27,8 +27,7 @@ namespace pmr {
 // [mem.res.monotonic.buffer]
 
 class _LIBCPP_AVAILABILITY_PMR _LIBCPP_EXPORTED_FROM_ABI monotonic_buffer_resource : public memory_resource {
-  static const size_t __default_buffer_capacity  = 1024;
-  static const size_t __default_buffer_alignment = 16;
+  static constexpr size_t __default_buffer_capacity = 1024;
 
   struct __chunk_footer {
     __chunk_footer* __next_;
@@ -38,7 +37,6 @@ class _LIBCPP_AVAILABILITY_PMR _LIBCPP_EXPORTED_FROM_ABI monotonic_buffer_resour
     _LIBCPP_HIDE_FROM_ABI size_t __allocation_size() {
       return (reinterpret_cast<char*>(this) - __start_) + sizeof(*this);
     }
-    void* __try_allocate_from_chunk(size_t, size_t);
   };
 
   struct __initial_descriptor {
@@ -48,7 +46,6 @@ class _LIBCPP_AVAILABILITY_PMR _LIBCPP_EXPORTED_FROM_ABI monotonic_buffer_resour
       char* __end_;
       size_t __size_;
     };
-    void* __try_allocate_from_chunk(size_t, size_t);
   };
 
 public:
diff --git a/libcxx/lib/abi/CHANGELOG.TXT b/libcxx/lib/abi/CHANGELOG.TXT
@@ -16,6 +16,17 @@ New entries should be added directly below the "Version" header.
 Version 20.0
 ------------
 
+* [libc++][PMR] Remove duplicate implementation of __try_allocate_from_chunk
+
+  This patch removes member functions __try_allocate_from_chunk from __chunk_footer and __initial_descriptor.
+  The two implementations were almost identical and can be easily moved to be implementation details of the built library.
+  Since they were only used from within the built library, the removal of these symbols should not be an ABI break.
+
+  All platforms
+  -------------
+  Symbol removed: _ZNSt3__13pmr25monotonic_buffer_resource14__chunk_footer25__try_allocate_from_chunkEmm
+  Symbol removed: _ZNSt3__13pmr25monotonic_buffer_resource20__initial_descriptor25__try_allocate_from_chunkEmm
+
 * [libc++] Remove the pointer safety functions from the dylib
 
   The pointer safety functions were never implemented by anyone in a non-trivial
diff --git a/libcxx/lib/abi/arm64-apple-darwin.libcxxabi.v1.stable.exceptions.nonew.abilist b/libcxx/lib/abi/arm64-apple-darwin.libcxxabi.v1.stable.exceptions.nonew.abilist
@@ -1594,8 +1594,6 @@
 {'is_defined': True, 'name': '__ZNSt3__13pmr20null_memory_resourceEv', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__ZNSt3__13pmr20set_default_resourceEPNS0_15memory_resourceE', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__ZNSt3__13pmr25monotonic_buffer_resource11do_allocateEmm', 'type': 'FUNC'}
-{'is_defined': True, 'name': '__ZNSt3__13pmr25monotonic_buffer_resource14__chunk_footer25__try_allocate_from_chunkEmm', 'type': 'FUNC'}
-{'is_defined': True, 'name': '__ZNSt3__13pmr25monotonic_buffer_resource20__initial_descriptor25__try_allocate_from_chunkEmm', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__ZNSt3__13pmr28unsynchronized_pool_resource11do_allocateEmm', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__ZNSt3__13pmr28unsynchronized_pool_resource12__adhoc_pool13__do_allocateEPNS0_15memory_resourceEmm', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__ZNSt3__13pmr28unsynchronized_pool_resource12__adhoc_pool13__release_ptrEPNS0_15memory_resourceE', 'type': 'FUNC'}
diff --git a/libcxx/lib/abi/i686-linux-android21.libcxxabi.v1.stable.exceptions.nonew.abilist b/libcxx/lib/abi/i686-linux-android21.libcxxabi.v1.stable.exceptions.nonew.abilist
@@ -1230,8 +1230,6 @@
 {'is_defined': True, 'name': '_ZNSt6__ndk13pmr20null_memory_resourceEv', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt6__ndk13pmr20set_default_resourceEPNS0_15memory_resourceE', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt6__ndk13pmr25monotonic_buffer_resource11do_allocateEjj', 'type': 'FUNC'}
-{'is_defined': True, 'name': '_ZNSt6__ndk13pmr25monotonic_buffer_resource14__chunk_footer25__try_allocate_from_chunkEjj', 'type': 'FUNC'}
-{'is_defined': True, 'name': '_ZNSt6__ndk13pmr25monotonic_buffer_resource20__initial_descriptor25__try_allocate_from_chunkEjj', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt6__ndk13pmr28unsynchronized_pool_resource11do_allocateEjj', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt6__ndk13pmr28unsynchronized_pool_resource12__adhoc_pool13__do_allocateEPNS0_15memory_resourceEjj', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt6__ndk13pmr28unsynchronized_pool_resource12__adhoc_pool13__release_ptrEPNS0_15memory_resourceE', 'type': 'FUNC'}
diff --git a/libcxx/lib/abi/powerpc-ibm-aix.libcxxabi.v1.stable.exceptions.nonew.abilist b/libcxx/lib/abi/powerpc-ibm-aix.libcxxabi.v1.stable.exceptions.nonew.abilist
@@ -580,8 +580,6 @@
 {'import_export': 'EXP', 'is_defined': True, 'name': '_ZNSt3__13pmr20null_memory_resourceEv', 'storage_mapping_class': 'DS', 'type': 'FUNC'}
 {'import_export': 'EXP', 'is_defined': True, 'name': '_ZNSt3__13pmr20set_default_resourceEPNS0_15memory_resourceE', 'storage_mapping_class': 'DS', 'type': 'FUNC'}
 {'import_export': 'EXP', 'is_defined': True, 'name': '_ZNSt3__13pmr25monotonic_buffer_resource11do_allocateEmm', 'storage_mapping_class': 'DS', 'type': 'FUNC'}
-{'import_export': 'EXP', 'is_defined': True, 'name': '_ZNSt3__13pmr25monotonic_buffer_resource14__chunk_footer25__try_allocate_from_chunkEmm', 'storage_mapping_class': 'DS', 'type': 'FUNC'}
-{'import_export': 'EXP', 'is_defined': True, 'name': '_ZNSt3__13pmr25monotonic_buffer_resource20__initial_descriptor25__try_allocate_from_chunkEmm', 'storage_mapping_class': 'DS', 'type': 'FUNC'}
 {'import_export': 'EXP', 'is_defined': True, 'name': '_ZNSt3__13pmr28unsynchronized_pool_resource11do_allocateEmm', 'storage_mapping_class': 'DS', 'type': 'FUNC'}
 {'import_export': 'EXP', 'is_defined': True, 'name': '_ZNSt3__13pmr28unsynchronized_pool_resource12__adhoc_pool13__do_allocateEPNS0_15memory_resourceEmm', 'storage_mapping_class': 'DS', 'type': 'FUNC'}
 {'import_export': 'EXP', 'is_defined': True, 'name': '_ZNSt3__13pmr28unsynchronized_pool_resource12__adhoc_pool13__release_ptrEPNS0_15memory_resourceE', 'storage_mapping_class': 'DS', 'type': 'FUNC'}
diff --git a/libcxx/lib/abi/powerpc64-ibm-aix.libcxxabi.v1.stable.exceptions.nonew.abilist b/libcxx/lib/abi/powerpc64-ibm-aix.libcxxabi.v1.stable.exceptions.nonew.abilist
@@ -580,8 +580,6 @@
 {'import_export': 'EXP', 'is_defined': True, 'name': '_ZNSt3__13pmr20null_memory_resourceEv', 'storage_mapping_class': 'DS', 'type': 'FUNC'}
 {'import_export': 'EXP', 'is_defined': True, 'name': '_ZNSt3__13pmr20set_default_resourceEPNS0_15memory_resourceE', 'storage_mapping_class': 'DS', 'type': 'FUNC'}
 {'import_export': 'EXP', 'is_defined': True, 'name': '_ZNSt3__13pmr25monotonic_buffer_resource11do_allocateEmm', 'storage_mapping_class': 'DS', 'type': 'FUNC'}
-{'import_export': 'EXP', 'is_defined': True, 'name': '_ZNSt3__13pmr25monotonic_buffer_resource14__chunk_footer25__try_allocate_from_chunkEmm', 'storage_mapping_class': 'DS', 'type': 'FUNC'}
-{'import_export': 'EXP', 'is_defined': True, 'name': '_ZNSt3__13pmr25monotonic_buffer_resource20__initial_descriptor25__try_allocate_from_chunkEmm', 'storage_mapping_class': 'DS', 'type': 'FUNC'}
 {'import_export': 'EXP', 'is_defined': True, 'name': '_ZNSt3__13pmr28unsynchronized_pool_resource11do_allocateEmm', 'storage_mapping_class': 'DS', 'type': 'FUNC'}
 {'import_export': 'EXP', 'is_defined': True, 'name': '_ZNSt3__13pmr28unsynchronized_pool_resource12__adhoc_pool13__do_allocateEPNS0_15memory_resourceEmm', 'storage_mapping_class': 'DS', 'type': 'FUNC'}
 {'import_export': 'EXP', 'is_defined': True, 'name': '_ZNSt3__13pmr28unsynchronized_pool_resource12__adhoc_pool13__release_ptrEPNS0_15memory_resourceE', 'storage_mapping_class': 'DS', 'type': 'FUNC'}
diff --git a/libcxx/lib/abi/x86_64-apple-darwin.libcxxabi.v1.stable.exceptions.nonew.abilist b/libcxx/lib/abi/x86_64-apple-darwin.libcxxabi.v1.stable.exceptions.nonew.abilist
@@ -1594,8 +1594,6 @@
 {'is_defined': True, 'name': '__ZNSt3__13pmr20null_memory_resourceEv', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__ZNSt3__13pmr20set_default_resourceEPNS0_15memory_resourceE', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__ZNSt3__13pmr25monotonic_buffer_resource11do_allocateEmm', 'type': 'FUNC'}
-{'is_defined': True, 'name': '__ZNSt3__13pmr25monotonic_buffer_resource14__chunk_footer25__try_allocate_from_chunkEmm', 'type': 'FUNC'}
-{'is_defined': True, 'name': '__ZNSt3__13pmr25monotonic_buffer_resource20__initial_descriptor25__try_allocate_from_chunkEmm', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__ZNSt3__13pmr28unsynchronized_pool_resource11do_allocateEmm', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__ZNSt3__13pmr28unsynchronized_pool_resource12__adhoc_pool13__do_allocateEPNS0_15memory_resourceEmm', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__ZNSt3__13pmr28unsynchronized_pool_resource12__adhoc_pool13__release_ptrEPNS0_15memory_resourceE', 'type': 'FUNC'}
diff --git a/libcxx/lib/abi/x86_64-linux-android21.libcxxabi.v1.stable.exceptions.nonew.abilist b/libcxx/lib/abi/x86_64-linux-android21.libcxxabi.v1.stable.exceptions.nonew.abilist
@@ -1230,8 +1230,6 @@
 {'is_defined': True, 'name': '_ZNSt6__ndk13pmr20null_memory_resourceEv', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt6__ndk13pmr20set_default_resourceEPNS0_15memory_resourceE', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt6__ndk13pmr25monotonic_buffer_resource11do_allocateEmm', 'type': 'FUNC'}
-{'is_defined': True, 'name': '_ZNSt6__ndk13pmr25monotonic_buffer_resource14__chunk_footer25__try_allocate_from_chunkEmm', 'type': 'FUNC'}
-{'is_defined': True, 'name': '_ZNSt6__ndk13pmr25monotonic_buffer_resource20__initial_descriptor25__try_allocate_from_chunkEmm', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt6__ndk13pmr28unsynchronized_pool_resource11do_allocateEmm', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt6__ndk13pmr28unsynchronized_pool_resource12__adhoc_pool13__do_allocateEPNS0_15memory_resourceEmm', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt6__ndk13pmr28unsynchronized_pool_resource12__adhoc_pool13__release_ptrEPNS0_15memory_resourceE', 'type': 'FUNC'}
diff --git a/libcxx/lib/abi/x86_64-unknown-freebsd.libcxxabi.v1.stable.exceptions.nonew.abilist b/libcxx/lib/abi/x86_64-unknown-freebsd.libcxxabi.v1.stable.exceptions.nonew.abilist
@@ -1245,8 +1245,6 @@
 {'is_defined': True, 'name': '_ZNSt3__13pmr20null_memory_resourceEv', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt3__13pmr20set_default_resourceEPNS0_15memory_resourceE', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt3__13pmr25monotonic_buffer_resource11do_allocateEmm', 'type': 'FUNC'}
-{'is_defined': True, 'name': '_ZNSt3__13pmr25monotonic_buffer_resource14__chunk_footer25__try_allocate_from_chunkEmm', 'type': 'FUNC'}
-{'is_defined': True, 'name': '_ZNSt3__13pmr25monotonic_buffer_resource20__initial_descriptor25__try_allocate_from_chunkEmm', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt3__13pmr28unsynchronized_pool_resource11do_allocateEmm', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt3__13pmr28unsynchronized_pool_resource12__adhoc_pool13__do_allocateEPNS0_15memory_resourceEmm', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt3__13pmr28unsynchronized_pool_resource12__adhoc_pool13__release_ptrEPNS0_15memory_resourceE', 'type': 'FUNC'}
diff --git a/libcxx/lib/abi/x86_64-unknown-linux-gnu.libcxxabi.v1.stable.exceptions.nonew.abilist b/libcxx/lib/abi/x86_64-unknown-linux-gnu.libcxxabi.v1.stable.exceptions.nonew.abilist
@@ -1243,8 +1243,6 @@
 {'is_defined': True, 'name': '_ZNSt3__13pmr20null_memory_resourceEv', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt3__13pmr20set_default_resourceEPNS0_15memory_resourceE', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt3__13pmr25monotonic_buffer_resource11do_allocateEmm', 'type': 'FUNC'}
-{'is_defined': True, 'name': '_ZNSt3__13pmr25monotonic_buffer_resource14__chunk_footer25__try_allocate_from_chunkEmm', 'type': 'FUNC'}
-{'is_defined': True, 'name': '_ZNSt3__13pmr25monotonic_buffer_resource20__initial_descriptor25__try_allocate_from_chunkEmm', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt3__13pmr28unsynchronized_pool_resource11do_allocateEmm', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt3__13pmr28unsynchronized_pool_resource12__adhoc_pool13__do_allocateEPNS0_15memory_resourceEmm', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt3__13pmr28unsynchronized_pool_resource12__adhoc_pool13__release_ptrEPNS0_15memory_resourceE', 'type': 'FUNC'}
diff --git a/libcxx/lib/abi/x86_64-unknown-linux-gnu.libcxxabi.v1.stable.noexceptions.nonew.abilist b/libcxx/lib/abi/x86_64-unknown-linux-gnu.libcxxabi.v1.stable.noexceptions.nonew.abilist
@@ -1214,8 +1214,6 @@
 {'is_defined': True, 'name': '_ZNSt3__13pmr20null_memory_resourceEv', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt3__13pmr20set_default_resourceEPNS0_15memory_resourceE', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt3__13pmr25monotonic_buffer_resource11do_allocateEmm', 'type': 'FUNC'}
-{'is_defined': True, 'name': '_ZNSt3__13pmr25monotonic_buffer_resource14__chunk_footer25__try_allocate_from_chunkEmm', 'type': 'FUNC'}
-{'is_defined': True, 'name': '_ZNSt3__13pmr25monotonic_buffer_resource20__initial_descriptor25__try_allocate_from_chunkEmm', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt3__13pmr28unsynchronized_pool_resource11do_allocateEmm', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt3__13pmr28unsynchronized_pool_resource12__adhoc_pool13__do_allocateEPNS0_15memory_resourceEmm', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt3__13pmr28unsynchronized_pool_resource12__adhoc_pool13__release_ptrEPNS0_15memory_resourceE', 'type': 'FUNC'}
diff --git a/libcxx/src/memory_resource.cpp b/libcxx/src/memory_resource.cpp
@@ -413,6 +413,8 @@ bool synchronized_pool_resource::do_is_equal(const memory_resource& other) const
 
 // 23.12.6, mem.res.monotonic.buffer
 
+constexpr size_t __default_growth_factor = 2;
+
 static void* align_down(size_t align, size_t size, void*& ptr, size_t& space) {
   if (size > space)
     return nullptr;
@@ -429,23 +431,20 @@ static void* align_down(size_t align, size_t size, void*& ptr, size_t& space) {
   return ptr;
 }
 
-void* monotonic_buffer_resource::__initial_descriptor::__try_allocate_from_chunk(size_t bytes, size_t align) {
-  if (!__cur_)
-    return nullptr;
-  void* new_ptr       = static_cast<void*>(__cur_);
-  size_t new_capacity = (__cur_ - __start_);
-  void* aligned_ptr   = align_down(align, bytes, new_ptr, new_capacity);
-  if (aligned_ptr != nullptr)
-    __cur_ = static_cast<char*>(new_ptr);
-  return aligned_ptr;
-}
-
-void* monotonic_buffer_resource::__chunk_footer::__try_allocate_from_chunk(size_t bytes, size_t align) {
-  void* new_ptr       = static_cast<void*>(__cur_);
-  size_t new_capacity = (__cur_ - __start_);
+template <bool is_initial, typename Chunk>
+void* __try_allocate_from_chunk(Chunk& self, size_t bytes, size_t align) {
+  if constexpr (is_initial) {
+    // only for __initial_descriptor.
+    // if __initial_descriptor.__cur_ equals nullptr, means no available buffer given when ctor.
+    // here we just return nullptr, let the caller do the next handling.
+    if (!self.__cur_)
+      return nullptr;
+  }
+  void* new_ptr       = static_cast<void*>(self.__cur_);
+  size_t new_capacity = (self.__cur_ - self.__start_);
   void* aligned_ptr   = align_down(align, bytes, new_ptr, new_capacity);
   if (aligned_ptr != nullptr)
-    __cur_ = static_cast<char*>(new_ptr);
+    self.__cur_ = static_cast<char*>(new_ptr);
   return aligned_ptr;
 }
 
@@ -462,10 +461,10 @@ void* monotonic_buffer_resource::do_allocate(size_t bytes, size_t align) {
     return roundup(newsize, footer_align) + footer_size;
   };
 
-  if (void* result = __initial_.__try_allocate_from_chunk(bytes, align))
+  if (void* result = __try_allocate_from_chunk<true, __initial_descriptor>(__initial_, bytes, align))
     return result;
   if (__chunks_ != nullptr) {
-    if (void* result = __chunks_->__try_allocate_from_chunk(bytes, align))
+    if (void* result = __try_allocate_from_chunk<false, __chunk_footer>(*__chunks_, bytes, align))
       return result;
   }
 
@@ -478,7 +477,7 @@ void* monotonic_buffer_resource::do_allocate(size_t bytes, size_t align) {
   size_t previous_capacity = previous_allocation_size();
 
   if (aligned_capacity <= previous_capacity) {
-    size_t newsize   = 2 * (previous_capacity - footer_size);
+    size_t newsize   = __default_growth_factor * (previous_capacity - footer_size);
     aligned_capacity = roundup(newsize, footer_align) + footer_size;
   }
 
@@ -491,7 +490,7 @@ void* monotonic_buffer_resource::do_allocate(size_t bytes, size_t align) {
   footer->__align_       = align;
   __chunks_              = footer;
 
-  return __chunks_->__try_allocate_from_chunk(bytes, align);
+  return __try_allocate_from_chunk<false, __chunk_footer>(*__chunks_, bytes, align);
 }
 
 } // namespace pmr
