//===- llvm/Analysis/LoopInfo.h - Natural Loop Calculator --------*- C++ -*--=//
//
// This file defines the LoopInfo class that is used to identify natural loops
-// and determine the loop depth of various nodes of the CFG. Note that the
-// loops identified may actually be several natural loops that share the same
-// header node... not just a single natural loop.
+// and determine the loop depth of various nodes of the CFG. Note that natural
+// loops may actually be several loops that share the same header node...
+//
+// This analysis calculates the nesting structure of loops in a function. For
+// each natural loop identified, this analysis identifies natural loops
+// contained entirely within the function, the basic blocks the make up the
+// loop, the nesting depth of the loop, and the successor blocks of the loop.
+//
+// It can calculate on the fly a variety of different bits of information, such
+// as whether there is a preheader for the loop, the number of back edges to the
+// header, and whether or not a particular block branches out of the loop.
//
//===----------------------------------------------------------------------===//
///
class Loop {
Loop *ParentLoop;
- std::vector<BasicBlock *> Blocks; // First entry is the header node
std::vector<Loop*> SubLoops; // Loops contained entirely within this one
+ std::vector<BasicBlock *> Blocks; // First entry is the header node
+ std::vector<BasicBlock *> ExitBlocks; // Reachable blocks outside the loop
unsigned LoopDepth; // Nesting depth of this loop
Loop(const Loop &); // DO NOT IMPLEMENT
/// getSubLoops - Return the loops contained entirely within this loop
///
- inline const std::vector<Loop*> &getSubLoops() const { return SubLoops; }
- inline const std::vector<BasicBlock*> &getBlocks() const { return Blocks; }
+ const std::vector<Loop*> &getSubLoops() const { return SubLoops; }
+
+ /// getBlocks - Get a list of the basic blocks which make up this loop.
+ ///
+ const std::vector<BasicBlock*> &getBlocks() const { return Blocks; }
+
+ /// getExitBlocks - Return all of the successor blocks of this loop. These
+ /// are the blocks _outside of the current loop_ which are branched to.
+ ///
+ const std::vector<BasicBlock*> &getExitBlocks() const { return ExitBlocks; }
/// isLoopExit - True if terminator in the block can branch to another block
- /// that is outside of the current loop.
+ /// that is outside of the current loop. The reached block should be in the
+ /// ExitBlocks list.
+ ///
bool isLoopExit(const BasicBlock *BB) const;
- /// Find number of back edges
+ /// getNumBackEdges - Calculate the number of back edges to the loop header
+ ///
unsigned getNumBackEdges() const;
/// getLoopPreheader - If there is a preheader for this loop, return it. A
///
BasicBlock *getLoopPreheader() const;
- /// addBasicBlockToLoop - This function is used by other analyses to update
- /// loop information. NewBB is set to be a new member of the current loop.
+ /// addBasicBlockToLoop - This method is used by other analyses to update loop
+ /// information. NewBB is set to be a new member of the current loop.
/// Because of this, it is added as a member of all parent loops, and is added
/// to the specified LoopInfo object as being in the current basic block. It
/// is not valid to replace the loop header with this method.
///
void addBasicBlockToLoop(BasicBlock *NewBB, LoopInfo &LI);
+ /// changeExitBlock - This method is used to update loop information. One
+ /// instance of the specified Old basic block is removed from the exit list
+ /// and replaced with New.
+ ///
+ void changeExitBlock(BasicBlock *Old, BasicBlock *New);
+
void print(std::ostream &O) const;
private:
friend class LoopInfo;
return L ? L->getLoopDepth() : 0;
}
-#if 0
// isLoopHeader - True if the block is a loop header node
bool isLoopHeader(BasicBlock *BB) const {
return getLoopFor(BB)->getHeader() == BB;
}
- // isLoopEnd - True if block jumps to loop entry
- bool isLoopEnd(BasicBlock *BB) const;
-#endif
/// runOnFunction - Calculate the natural loop information.
///