[libc][NFC] Remove template arguments from Block (#117386)

Author: mysterymath

libc/src/__support/block.h

@@ -68,13 +68,11 @@ using cpp::optional;
 /// The blocks store their offsets to the previous and next blocks. The latter
 /// is also the block's size.
 ///
-/// The `ALIGNMENT` constant provided by the derived block is typically the
-/// minimum value of `alignof(OffsetType)`. Blocks will always be aligned to a
-/// `ALIGNMENT` boundary. Block sizes will always be rounded up to a multiple of
-/// `ALIGNMENT`.
+/// Blocks will always be aligned to a `ALIGNMENT` boundary. Block sizes will
+/// always be rounded up to a multiple of `ALIGNMENT`.
 ///
-/// As an example, the diagram below represents two contiguous
-/// `Block<uint32_t, 8>`s. The indices indicate byte offsets:
+/// As an example, the diagram below represents two contiguous `Block`s. The
+/// indices indicate byte offsets:
 ///
 /// @code{.unparsed}
 /// Block 1:
@@ -117,30 +115,15 @@ using cpp::optional;
 ///
 /// The next offset of a block matches the previous offset of its next block.
 /// The first block in a list is denoted by having a previous offset of `0`.
-///
-/// @tparam   OffsetType  Unsigned integral type used to encode offsets. Larger
-///                       types can address more memory, but consume greater
-///                       overhead.
-/// @tparam   kAlign      Sets the overall alignment for blocks. Minimum is
-///                       `alignof(OffsetType)`, but the default is max_align_t,
-///                       since the usable space will then already be
-///                       aligned to max_align_t if the size of OffsetType is no
-///                       less than half of max_align_t. Larger values cause
-///                       greater overhead.
-template <typename OffsetType = uintptr_t, size_t kAlign = alignof(max_align_t)>
 class Block {
   // Masks for the contents of the next_ field.
   static constexpr size_t PREV_FREE_MASK = 1 << 0;
   static constexpr size_t LAST_MASK = 1 << 1;
   static constexpr size_t SIZE_MASK = ~(PREV_FREE_MASK | LAST_MASK);
 
 public:
-  using offset_type = OffsetType;
-  static_assert(cpp::is_unsigned_v<offset_type>,
-                "offset type must be unsigned");
-  static constexpr size_t ALIGNMENT =
-      cpp::max(cpp::max(kAlign, alignof(offset_type)), size_t{4});
-  static constexpr size_t BLOCK_OVERHEAD = align_up(sizeof(Block), ALIGNMENT);
+  static constexpr size_t ALIGNMENT = cpp::max(alignof(max_align_t), size_t{4});
+  static const size_t BLOCK_OVERHEAD;
 
   // No copy or move.
   Block(const Block &other) = delete;
@@ -157,61 +140,61 @@ class Block {
   ///
   /// @warning  This method does not do any checking; passing a random
   ///           pointer will return a non-null pointer.
-  static Block *from_usable_space(void *usable_space) {
+  LIBC_INLINE static Block *from_usable_space(void *usable_space) {
     auto *bytes = reinterpret_cast<cpp::byte *>(usable_space);
     return reinterpret_cast<Block *>(bytes - BLOCK_OVERHEAD);
   }
-  static const Block *from_usable_space(const void *usable_space) {
+  LIBC_INLINE static const Block *from_usable_space(const void *usable_space) {
     const auto *bytes = reinterpret_cast<const cpp::byte *>(usable_space);
     return reinterpret_cast<const Block *>(bytes - BLOCK_OVERHEAD);
   }
 
   /// @returns The total size of the block in bytes, including the header.
-  size_t outer_size() const { return next_ & SIZE_MASK; }
+  LIBC_INLINE size_t outer_size() const { return next_ & SIZE_MASK; }
 
-  static size_t outer_size(size_t inner_size) {
+  LIBC_INLINE static size_t outer_size(size_t inner_size) {
     // The usable region includes the prev_ field of the next block.
     return inner_size - sizeof(prev_) + BLOCK_OVERHEAD;
   }
 
   /// @returns The number of usable bytes inside the block were it to be
   /// allocated.
-  size_t inner_size() const {
+  LIBC_INLINE size_t inner_size() const {
     if (!next())
       return 0;
     return inner_size(outer_size());
   }
 
   /// @returns The number of usable bytes inside a block with the given outer
   /// size were it to be allocated.
-  static size_t inner_size(size_t outer_size) {
+  LIBC_INLINE static size_t inner_size(size_t outer_size) {
     // The usable region includes the prev_ field of the next block.
     return inner_size_free(outer_size) + sizeof(prev_);
   }
 
   /// @returns The number of usable bytes inside the block if it remains free.
-  size_t inner_size_free() const {
+  LIBC_INLINE size_t inner_size_free() const {
     if (!next())
       return 0;
     return inner_size_free(outer_size());
   }
 
   /// @returns The number of usable bytes inside a block with the given outer
   /// size if it remains free.
-  static size_t inner_size_free(size_t outer_size) {
+  LIBC_INLINE static size_t inner_size_free(size_t outer_size) {
     return outer_size - BLOCK_OVERHEAD;
   }
 
   /// @returns A pointer to the usable space inside this block.
-  cpp::byte *usable_space() {
+  LIBC_INLINE cpp::byte *usable_space() {
     return reinterpret_cast<cpp::byte *>(this) + BLOCK_OVERHEAD;
   }
-  const cpp::byte *usable_space() const {
+  LIBC_INLINE const cpp::byte *usable_space() const {
     return reinterpret_cast<const cpp::byte *>(this) + BLOCK_OVERHEAD;
   }
 
   // @returns The region of memory the block manages, including the header.
-  ByteSpan region() {
+  LIBC_INLINE ByteSpan region() {
     return {reinterpret_cast<cpp::byte *>(this), outer_size()};
   }
 
@@ -229,42 +212,53 @@ class Block {
 
   /// @returns The block immediately after this one, or a null pointer if this
   /// is the last block.
-  Block *next() const;
+  LIBC_INLINE Block *next() const {
+    if (next_ & LAST_MASK)
+      return nullptr;
+    return reinterpret_cast<Block *>(reinterpret_cast<uintptr_t>(this) +
+                                     outer_size());
+  }
 
   /// @returns The free block immediately before this one, otherwise nullptr.
-  Block *prev_free() const;
+  LIBC_INLINE Block *prev_free() const {
+    if (!(next_ & PREV_FREE_MASK))
+      return nullptr;
+    return reinterpret_cast<Block *>(reinterpret_cast<uintptr_t>(this) - prev_);
+  }
 
   /// @returns Whether the block is unavailable for allocation.
-  bool used() const { return !next() || !next()->prev_free(); }
+  LIBC_INLINE bool used() const { return !next() || !next()->prev_free(); }
 
   /// Marks this block as in use.
-  void mark_used() {
+  LIBC_INLINE void mark_used() {
     LIBC_ASSERT(next() && "last block is always considered used");
     next()->next_ &= ~PREV_FREE_MASK;
   }
 
   /// Marks this block as free.
-  void mark_free() {
+  LIBC_INLINE void mark_free() {
     LIBC_ASSERT(next() && "last block is always considered used");
     next()->next_ |= PREV_FREE_MASK;
     // The next block's prev_ field becomes alive, as it is no longer part of
     // this block's used space.
-    *new (&next()->prev_) offset_type = outer_size();
+    *new (&next()->prev_) size_t = outer_size();
   }
 
   /// Marks this block as the last one in the chain. Makes next() return
   /// nullptr.
-  void mark_last() { next_ |= LAST_MASK; }
+  LIBC_INLINE void mark_last() { next_ |= LAST_MASK; }
 
-  constexpr Block(size_t outer_size);
+  LIBC_INLINE constexpr Block(size_t outer_size) : next_(outer_size) {
+    LIBC_ASSERT(outer_size % ALIGNMENT == 0 && "block sizes must be aligned");
+  }
 
-  bool is_usable_space_aligned(size_t alignment) const {
+  LIBC_INLINE bool is_usable_space_aligned(size_t alignment) const {
     return reinterpret_cast<uintptr_t>(usable_space()) % alignment == 0;
   }
 
   /// @returns The new inner size of this block that would give the usable
   /// space of the next block the given alignment.
-  size_t padding_for_alignment(size_t alignment) const {
+  LIBC_INLINE size_t padding_for_alignment(size_t alignment) const {
     if (is_usable_space_aligned(alignment))
       return 0;
 
@@ -322,7 +316,9 @@ class Block {
 private:
   /// Construct a block to represent a span of bytes. Overwrites only enough
   /// memory for the block header; the rest of the span is left alone.
-  static Block *as_block(ByteSpan bytes);
+  LIBC_INLINE static Block *as_block(ByteSpan bytes) {
+    return ::new (bytes.data()) Block(bytes.size());
+  }
 
   /// Like `split`, but assumes the caller has already checked to parameters to
   /// ensure the split will succeed.
@@ -332,11 +328,11 @@ class Block {
   /// block. This field is only alive when the previous block is free;
   /// otherwise, its memory is reused as part of the previous block's usable
   /// space.
-  offset_type prev_ = 0;
+  size_t prev_ = 0;
 
   /// Offset from this block to the next block. Valid even if this is the last
   /// block, since it equals the size of the block.
-  offset_type next_ = 0;
+  size_t next_ = 0;
 
   /// Information about the current state of the block is stored in the two low
   /// order bits of the next_ value. These are guaranteed free by a minimum
@@ -347,9 +343,10 @@ class Block {
   ///   previous block is free.
   /// * If the `last` flag is set, the block is the sentinel last block. It is
   ///   summarily considered used and has no next block.
-} __attribute__((packed, aligned(cpp::max(kAlign, size_t{4}))));
+} __attribute__((packed, aligned(cpp::max(alignof(max_align_t), size_t{4}))));
 
-// Public template method implementations.
+inline constexpr size_t Block::BLOCK_OVERHEAD =
+    align_up(sizeof(Block), ALIGNMENT);
 
 LIBC_INLINE ByteSpan get_aligned_subspan(ByteSpan bytes, size_t alignment) {
   if (bytes.data() == nullptr)
@@ -367,9 +364,8 @@ LIBC_INLINE ByteSpan get_aligned_subspan(ByteSpan bytes, size_t alignment) {
                        aligned_end - aligned_start);
 }
 
-template <typename OffsetType, size_t kAlign>
-optional<Block<OffsetType, kAlign> *>
-Block<OffsetType, kAlign>::init(ByteSpan region) {
+LIBC_INLINE
+optional<Block *> Block::init(ByteSpan region) {
   optional<ByteSpan> result = get_aligned_subspan(region, ALIGNMENT);
   if (!result)
     return {};
@@ -379,7 +375,7 @@ Block<OffsetType, kAlign>::init(ByteSpan region) {
   if (region.size() < 2 * BLOCK_OVERHEAD)
     return {};
 
-  if (cpp::numeric_limits<OffsetType>::max() < region.size())
+  if (cpp::numeric_limits<size_t>::max() < region.size())
     return {};
 
   Block *block = as_block(region.first(region.size() - BLOCK_OVERHEAD));
@@ -389,9 +385,8 @@ Block<OffsetType, kAlign>::init(ByteSpan region) {
   return block;
 }
 
-template <typename OffsetType, size_t kAlign>
-bool Block<OffsetType, kAlign>::can_allocate(size_t alignment,
-                                             size_t size) const {
+LIBC_INLINE
+bool Block::can_allocate(size_t alignment, size_t size) const {
   if (inner_size() < size)
     return false;
   if (is_usable_space_aligned(alignment))
@@ -406,10 +401,8 @@ bool Block<OffsetType, kAlign>::can_allocate(size_t alignment,
   return size <= aligned_inner_size;
 }
 
-template <typename OffsetType, size_t kAlign>
-typename Block<OffsetType, kAlign>::BlockInfo
-Block<OffsetType, kAlign>::allocate(Block *block, size_t alignment,
-                                    size_t size) {
+LIBC_INLINE
+Block::BlockInfo Block::allocate(Block *block, size_t alignment, size_t size) {
   LIBC_ASSERT(
       block->can_allocate(alignment, size) &&
       "Calls to this function for a given alignment and size should only be "
@@ -447,9 +440,8 @@ Block<OffsetType, kAlign>::allocate(Block *block, size_t alignment,
   return info;
 }
 
-template <typename OffsetType, size_t kAlign>
-optional<Block<OffsetType, kAlign> *>
-Block<OffsetType, kAlign>::split(size_t new_inner_size) {
+LIBC_INLINE
+optional<Block *> Block::split(size_t new_inner_size) {
   if (used())
     return {};
   // The prev_ field of the next block is always available, so there is a
@@ -469,9 +461,8 @@ Block<OffsetType, kAlign>::split(size_t new_inner_size) {
   return split_impl(new_inner_size);
 }
 
-template <typename OffsetType, size_t kAlign>
-Block<OffsetType, kAlign> *
-Block<OffsetType, kAlign>::split_impl(size_t new_inner_size) {
+LIBC_INLINE
+Block *Block::split_impl(size_t new_inner_size) {
   size_t outer_size1 = outer_size(new_inner_size);
   LIBC_ASSERT(outer_size1 % ALIGNMENT == 0 && "new size must be aligned");
   ByteSpan new_region = region().subspan(outer_size1);
@@ -484,8 +475,8 @@ Block<OffsetType, kAlign>::split_impl(size_t new_inner_size) {
   return new_block;
 }
 
-template <typename OffsetType, size_t kAlign>
-bool Block<OffsetType, kAlign>::merge_next() {
+LIBC_INLINE
+bool Block::merge_next() {
   if (used() || next()->used())
     return false;
   size_t new_size = outer_size() + next()->outer_size();
@@ -495,34 +486,6 @@ bool Block<OffsetType, kAlign>::merge_next() {
   return true;
 }
 
-template <typename OffsetType, size_t kAlign>
-Block<OffsetType, kAlign> *Block<OffsetType, kAlign>::next() const {
-  if (next_ & LAST_MASK)
-    return nullptr;
-  return reinterpret_cast<Block *>(reinterpret_cast<uintptr_t>(this) +
-                                   outer_size());
-}
-
-template <typename OffsetType, size_t kAlign>
-Block<OffsetType, kAlign> *Block<OffsetType, kAlign>::prev_free() const {
-  if (!(next_ & PREV_FREE_MASK))
-    return nullptr;
-  return reinterpret_cast<Block *>(reinterpret_cast<uintptr_t>(this) - prev_);
-}
-
-// Private template method implementations.
-
-template <typename OffsetType, size_t kAlign>
-constexpr Block<OffsetType, kAlign>::Block(size_t outer_size)
-    : next_(outer_size) {
-  LIBC_ASSERT(outer_size % ALIGNMENT == 0 && "block sizes must be aligned");
-}
-
-template <typename OffsetType, size_t kAlign>
-Block<OffsetType, kAlign> *Block<OffsetType, kAlign>::as_block(ByteSpan bytes) {
-  return ::new (bytes.data()) Block(bytes.size());
-}
-
 } // namespace LIBC_NAMESPACE_DECL
 
 #endif // LLVM_LIBC_SRC___SUPPORT_BLOCK_H

libc/src/__support/freelist.cpp

@@ -12,7 +12,7 @@ namespace LIBC_NAMESPACE_DECL {
 
 void FreeList::push(Node *node) {
   if (begin_) {
-    LIBC_ASSERT(Block<>::from_usable_space(node)->outer_size() ==
+    LIBC_ASSERT(Block::from_usable_space(node)->outer_size() ==
                     begin_->block()->outer_size() &&
                 "freelist entries must have the same size");
     // Since the list is circular, insert the node immediately before begin_.

libc/src/__support/freelist.h

@@ -26,12 +26,12 @@ class FreeList {
   class Node {
   public:
     /// @returns The block containing this node.
-    LIBC_INLINE const Block<> *block() const {
-      return Block<>::from_usable_space(this);
+    LIBC_INLINE const Block *block() const {
+      return Block::from_usable_space(this);
     }
 
     /// @returns The block containing this node.
-    LIBC_INLINE Block<> *block() { return Block<>::from_usable_space(this); }
+    LIBC_INLINE Block *block() { return Block::from_usable_space(this); }
 
     /// @returns The inner size of blocks in the list containing this node.
     LIBC_INLINE size_t size() const { return block()->inner_size(); }
@@ -58,11 +58,11 @@ class FreeList {
   LIBC_INLINE Node *begin() { return begin_; }
 
   /// @returns The first block in the list.
-  LIBC_INLINE Block<> *front() { return begin_->block(); }
+  LIBC_INLINE Block *front() { return begin_->block(); }
 
   /// Push a block to the back of the list.
   /// The block must be large enough to contain a node.
-  LIBC_INLINE void push(Block<> *block) {
+  LIBC_INLINE void push(Block *block) {
     LIBC_ASSERT(!block->used() &&
                 "only free blocks can be placed on free lists");
     LIBC_ASSERT(block->inner_size_free() >= sizeof(FreeList) &&