[CodeExtractor] Refactor extractCodeRegion, fix alloca emission.

llvm/include/llvm/Transforms/Utils/CodeExtractor.h

@@ -35,6 +35,7 @@ class Instruction;
 class Module;
 class Type;
 class Value;
+class StructType;
 
 /// A cache for the CodeExtractor analysis. The operation \ref
 /// CodeExtractor::extractCodeRegion is guaranteed not to invalidate this
@@ -101,12 +102,25 @@ class CodeExtractorAnalysisCache {
 
     // Bits of intermediate state computed at various phases of extraction.
     SetVector<BasicBlock *> Blocks;
-    unsigned NumExitBlocks = std::numeric_limits<unsigned>::max();
-    Type *RetTy;
 
-    // Mapping from the original exit blocks, to the new blocks inside
-    // the function.
-    SmallVector<BasicBlock *, 4> OldTargets;
+    /// Lists of blocks that are branched from the code region to be extracted,
+    /// also called the exit blocks. Each block is contained at most once. Its
+    /// order defines the return value of the extracted function.
+    ///
+    /// When there is just one (or no) exit block, the return value is
+    /// irrelevant.
+    ///
+    /// When there are exactly two exit blocks, the extracted function returns a
+    /// boolean. For SwitchCases[0], it returns 'true'. For SwitchCases[1] it
+    /// returns 'false'.
+    /// NOTE: Since a boolean is represented by i1, SwitchCases[0] returns 1 and
+    ///       SwitchCases[1] returns 0, which is inverted with the the regular
+    ///       switch case below.
+    ///
+    /// When there are 3 or more exit blocks, leaving the extracted function via
+    /// the first block it returns 0. When leaving via the second entry it
+    /// returns 1, etc.
+    SmallVector<BasicBlock *> SwitchCases;
 
     // Suffix to use when creating extracted function (appended to the original
     // function name + "."). If empty, the default is to use the entry block
@@ -238,26 +252,61 @@ class CodeExtractorAnalysisCache {
     getLifetimeMarkers(const CodeExtractorAnalysisCache &CEAC,
                        Instruction *Addr, BasicBlock *ExitBlock) const;
 
+    /// Updates the list of SwitchCases (corresponding to exit blocks) after
+    /// changes of the control flow or the Blocks list.
+    void recomputeSwitchCases();
+
+    /// Return the type used for the return code of the extracted function to
+    /// indicate which exit block to jump to.
+    Type *getSwitchType();
+
     void severSplitPHINodesOfEntry(BasicBlock *&Header);
-    void severSplitPHINodesOfExits(const SetVector<BasicBlock *> &Exits);
+    void severSplitPHINodesOfExits();
     void splitReturnBlocks();
 
-    Function *constructFunction(const ValueSet &inputs,
-                                const ValueSet &outputs,
-                                BasicBlock *header,
-                                BasicBlock *newRootNode, BasicBlock *newHeader,
-                                Function *oldFunction, Module *M);
-
     void moveCodeToFunction(Function *newFunction);
 
     void calculateNewCallTerminatorWeights(
         BasicBlock *CodeReplacer,
-        DenseMap<BasicBlock *, BlockFrequency> &ExitWeights,
+        const DenseMap<BasicBlock *, BlockFrequency> &ExitWeights,
         BranchProbabilityInfo *BPI);
 
-    CallInst *emitCallAndSwitchStatement(Function *newFunction,
-                                         BasicBlock *newHeader,
-                                         ValueSet &inputs, ValueSet &outputs);
+    /// Normalizes the control flow of the extracted regions, such as ensuring
+    /// that the extracted region does not contain a return instruction.
+    void normalizeCFGForExtraction(BasicBlock *&header);
+
+    /// Generates the function declaration for the function containing the
+    /// extracted code.
+    Function *constructFunctionDeclaration(const ValueSet &inputs,
+                                           const ValueSet &outputs,
+                                           BlockFrequency EntryFreq,
+                                           const Twine &Name,
+                                           ValueSet &StructValues,
+                                           StructType *&StructTy);
+
+    /// Generates the code for the extracted function. That is: a prolog, the
+    /// moved or copied code from the original function, and epilogs for each
+    /// exit.
+    void emitFunctionBody(const ValueSet &inputs, const ValueSet &outputs,
+                          const ValueSet &StructValues, Function *newFunction,
+                          StructType *StructArgTy, BasicBlock *header,
+                          const ValueSet &SinkingCands);
+
+    /// Generates a Basic Block that calls the extracted function.
+    CallInst *emitReplacerCall(const ValueSet &inputs, const ValueSet &outputs,
+                               const ValueSet &StructValues,
+                               Function *newFunction, StructType *StructArgTy,
+                               Function *oldFunction, BasicBlock *ReplIP,
+                               BlockFrequency EntryFreq,
+                               ArrayRef<Value *> LifetimesStart,
+                               std::vector<Value *> &Reloads);
+
+    /// Connects the basic block containing the call to the extracted function
+    /// into the original function's control flow.
+    void insertReplacerCall(
+        Function *oldFunction, BasicBlock *header, BasicBlock *codeReplacer,
+        const ValueSet &outputs, ArrayRef<Value *> Reloads,
+        const DenseMap<BasicBlock *, BlockFrequency> &ExitWeights);
   };
 
 } // end namespace llvm