[BOLT] Add function layout class

This patch adds a dedicated class to keep track of each function's
layout. It also lays the groundwork for splitting functions into
multiple fragments (as opposed to a strict hot/cold split).

Reviewed By: maksfb

Differential Revision: https://reviews.llvm.org/D129518

Author: Fabian Parzefall

bolt/include/bolt/Core/BinaryBasicBlock.h

@@ -15,6 +15,7 @@
 #ifndef BOLT_CORE_BINARY_BASIC_BLOCK_H
 #define BOLT_CORE_BINARY_BASIC_BLOCK_H
 
+#include "bolt/Core/FunctionLayout.h"
 #include "bolt/Core/MCPlus.h"
 #include "llvm/ADT/GraphTraits.h"
 #include "llvm/ADT/StringRef.h"
@@ -671,6 +672,10 @@ class BinaryBasicBlock {
 
   void markValid(const bool Valid) { IsValid = Valid; }
 
+  FragmentNum getFragmentNum() const {
+    return IsCold ? FragmentNum::cold() : FragmentNum::hot();
+  }
+
   bool isCold() const { return IsCold; }
 
   void setIsCold(const bool Flag) { IsCold = Flag; }

bolt/include/bolt/Core/BinaryFunction.h

@@ -30,6 +30,7 @@
 #include "bolt/Core/BinaryLoop.h"
 #include "bolt/Core/BinarySection.h"
 #include "bolt/Core/DebugData.h"
+#include "bolt/Core/FunctionLayout.h"
 #include "bolt/Core/JumpTable.h"
 #include "bolt/Core/MCPlus.h"
 #include "bolt/Utils/NameResolver.h"
@@ -552,10 +553,8 @@ class BinaryFunction {
   using BasicBlockListType = SmallVector<BinaryBasicBlock *, 0>;
   BasicBlockListType BasicBlocks;
   BasicBlockListType DeletedBasicBlocks;
-  BasicBlockOrderType BasicBlocksLayout;
-  /// Previous layout replaced by modifyLayout
-  BasicBlockOrderType BasicBlocksPreviousLayout;
-  bool ModifiedLayout{false};
+
+  FunctionLayout Layout;
 
   /// BasicBlockOffsets are used during CFG construction to map from code
   /// offsets to BinaryBasicBlocks.  Any modifications made to the CFG
@@ -754,12 +753,6 @@ class BinaryFunction {
   using const_reverse_iterator =
       pointee_iterator<BasicBlockListType::const_reverse_iterator>;
 
-  typedef BasicBlockOrderType::iterator order_iterator;
-  typedef BasicBlockOrderType::const_iterator const_order_iterator;
-  typedef BasicBlockOrderType::reverse_iterator reverse_order_iterator;
-  typedef BasicBlockOrderType::const_reverse_iterator
-      const_reverse_order_iterator;
-
   // CFG iterators.
   iterator                 begin()       { return BasicBlocks.begin(); }
   const_iterator           begin() const { return BasicBlocks.begin(); }
@@ -788,49 +781,6 @@ class BinaryFunction {
   BasicBlockListType::iterator pbegin()  { return BasicBlocks.begin(); }
   BasicBlockListType::iterator pend()    { return BasicBlocks.end(); }
 
-  order_iterator       layout_begin()    { return BasicBlocksLayout.begin(); }
-  const_order_iterator layout_begin()    const
-                                         { return BasicBlocksLayout.begin(); }
-  order_iterator       layout_end()      { return BasicBlocksLayout.end(); }
-  const_order_iterator layout_end()      const
-                                         { return BasicBlocksLayout.end(); }
-  reverse_order_iterator       layout_rbegin()
-                                         { return BasicBlocksLayout.rbegin(); }
-  const_reverse_order_iterator layout_rbegin() const
-                                         { return BasicBlocksLayout.rbegin(); }
-  reverse_order_iterator       layout_rend()
-                                         { return BasicBlocksLayout.rend(); }
-  const_reverse_order_iterator layout_rend()   const
-                                         { return BasicBlocksLayout.rend(); }
-  size_t   layout_size()  const { return BasicBlocksLayout.size(); }
-  bool     layout_empty() const { return BasicBlocksLayout.empty(); }
-  const BinaryBasicBlock *layout_front() const
-                                         { return BasicBlocksLayout.front(); }
-        BinaryBasicBlock *layout_front() { return BasicBlocksLayout.front(); }
-  const BinaryBasicBlock *layout_back()  const
-                                         { return BasicBlocksLayout.back(); }
-        BinaryBasicBlock *layout_back()  { return BasicBlocksLayout.back(); }
-
-  inline iterator_range<order_iterator> layout() {
-    return iterator_range<order_iterator>(BasicBlocksLayout.begin(),
-                                          BasicBlocksLayout.end());
-  }
-
-  inline iterator_range<const_order_iterator> layout() const {
-    return iterator_range<const_order_iterator>(BasicBlocksLayout.begin(),
-                                                BasicBlocksLayout.end());
-  }
-
-  inline iterator_range<reverse_order_iterator> rlayout() {
-    return iterator_range<reverse_order_iterator>(BasicBlocksLayout.rbegin(),
-                                                  BasicBlocksLayout.rend());
-  }
-
-  inline iterator_range<const_reverse_order_iterator> rlayout() const {
-    return iterator_range<const_reverse_order_iterator>(
-        BasicBlocksLayout.rbegin(), BasicBlocksLayout.rend());
-  }
-
   cfi_iterator        cie_begin()       { return CIEFrameInstructions.begin(); }
   const_cfi_iterator  cie_begin() const { return CIEFrameInstructions.begin(); }
   cfi_iterator        cie_end()         { return CIEFrameInstructions.end(); }
@@ -881,27 +831,16 @@ class BinaryFunction {
     return *this;
   }
 
-  /// Update layout of basic blocks used for output.
-  void updateBasicBlockLayout(BasicBlockOrderType &NewLayout) {
-    assert(NewLayout.size() == BasicBlocks.size() && "Layout size mismatch.");
+  FunctionLayout &getLayout() { return Layout; }
 
-    BasicBlocksPreviousLayout = BasicBlocksLayout;
-    if (NewLayout != BasicBlocksLayout) {
-      ModifiedLayout = true;
-      BasicBlocksLayout.clear();
-      BasicBlocksLayout.swap(NewLayout);
-    }
-  }
+  const FunctionLayout &getLayout() const { return Layout; }
 
   /// Recompute landing pad information for the function and all its blocks.
   void recomputeLandingPads();
 
-  /// Return current basic block layout.
-  const BasicBlockOrderType &getLayout() const { return BasicBlocksLayout; }
-
   /// Return a list of basic blocks sorted using DFS and update layout indices
   /// using the same order. Does not modify the current layout.
-  BasicBlockOrderType dfs() const;
+  BasicBlockListType dfs() const;
 
   /// Find the loops in the CFG of the function and store information about
   /// them.
@@ -958,26 +897,6 @@ class BinaryFunction {
     return I == LabelToBB.end() ? nullptr : I->second;
   }
 
-  /// Returns the basic block after the given basic block in the layout or
-  /// nullptr the last basic block is given.
-  const BinaryBasicBlock *getBasicBlockAfter(const BinaryBasicBlock *BB,
-                                             bool IgnoreSplits = true) const {
-    return const_cast<BinaryFunction *>(this)->getBasicBlockAfter(BB,
-                                                                  IgnoreSplits);
-  }
-
-  BinaryBasicBlock *getBasicBlockAfter(const BinaryBasicBlock *BB,
-                                       bool IgnoreSplits = true) {
-    for (auto I = layout_begin(), E = layout_end(); I != E; ++I) {
-      auto Next = std::next(I);
-      if (*I == BB && Next != E) {
-        return (IgnoreSplits || (*I)->isCold() == (*Next)->isCold()) ? *Next
-                                                                     : nullptr;
-      }
-    }
-    return nullptr;
-  }
-
   /// Retrieve the landing pad BB associated with invoke instruction \p Invoke
   /// that is in \p BB. Return nullptr if none exists
   BinaryBasicBlock *getLandingPadBBFor(const BinaryBasicBlock &BB,
@@ -1455,10 +1374,7 @@ class BinaryFunction {
   bool hasUnknownControlFlow() const { return HasUnknownControlFlow; }
 
   /// Return true if the function body is non-contiguous.
-  bool isSplit() const {
-    return isSimple() && layout_size() &&
-           layout_front()->isCold() != layout_back()->isCold();
-  }
+  bool isSplit() const { return isSimple() && getLayout().isSplit(); }
 
   bool shouldPreserveNops() const { return PreserveNops; }
 
@@ -1578,8 +1494,7 @@ class BinaryFunction {
     BinaryBasicBlock *BB = BasicBlocks.back();
 
     BB->setIndex(BasicBlocks.size() - 1);
-    BB->setLayoutIndex(layout_size());
-    BasicBlocksLayout.emplace_back(BB);
+    Layout.addBasicBlock(BB);
 
     return BB;
   }
@@ -1626,13 +1541,6 @@ class BinaryFunction {
   /// layout after the BB indicated by Start.
   void updateLayout(BinaryBasicBlock *Start, const unsigned NumNewBlocks);
 
-  /// Make sure basic blocks' indices match the current layout.
-  void updateLayoutIndices() const {
-    unsigned Index = 0;
-    for (BinaryBasicBlock *BB : layout())
-      BB->setLayoutIndex(Index++);
-  }
-
   /// Recompute the CFI state for NumNewBlocks following Start after inserting
   /// new blocks into the CFG.  This must be called after updateLayout.
   void updateCFIState(BinaryBasicBlock *Start, const unsigned NumNewBlocks);
@@ -2213,14 +2121,6 @@ class BinaryFunction {
   /// and size.
   uint64_t getFunctionScore() const;
 
-  /// Return true if the layout has been changed by basic block reordering,
-  /// false otherwise.
-  bool hasLayoutChanged() const;
-
-  /// Get the edit distance of the new layout with respect to the previous
-  /// layout after basic block reordering.
-  uint64_t getEditDistance() const;
-
   /// Get the number of instructions within this function.
   uint64_t getInstructionCount() const;
 
@@ -2429,7 +2329,7 @@ template <>
 struct GraphTraits<bolt::BinaryFunction *>
     : public GraphTraits<bolt::BinaryBasicBlock *> {
   static NodeRef getEntryNode(bolt::BinaryFunction *F) {
-    return *F->layout_begin();
+    return F->getLayout().block_front();
   }
 
   using nodes_iterator = pointer_iterator<bolt::BinaryFunction::iterator>;
@@ -2449,7 +2349,7 @@ template <>
 struct GraphTraits<const bolt::BinaryFunction *>
     : public GraphTraits<const bolt::BinaryBasicBlock *> {
   static NodeRef getEntryNode(const bolt::BinaryFunction *F) {
-    return *F->layout_begin();
+    return F->getLayout().block_front();
   }
 
   using nodes_iterator = pointer_iterator<bolt::BinaryFunction::const_iterator>;
@@ -2469,15 +2369,15 @@ template <>
 struct GraphTraits<Inverse<bolt::BinaryFunction *>>
     : public GraphTraits<Inverse<bolt::BinaryBasicBlock *>> {
   static NodeRef getEntryNode(Inverse<bolt::BinaryFunction *> G) {
-    return *G.Graph->layout_begin();
+    return G.Graph->getLayout().block_front();
   }
 };
 
 template <>
 struct GraphTraits<Inverse<const bolt::BinaryFunction *>>
     : public GraphTraits<Inverse<const bolt::BinaryBasicBlock *>> {
   static NodeRef getEntryNode(Inverse<const bolt::BinaryFunction *> G) {
-    return *G.Graph->layout_begin();
+    return G.Graph->getLayout().block_front();
   }
 };