+++ /dev/null
-//===-- CriticalEdge.cpp - Functions to detect and split critical edges ---===//
-//
-// These functions are here to detect and split critical edges in the CFG.
-//
-//===----------------------------------------------------------------------===//
-
-#include "llvm/Transforms/Utils/Local.h"
-#include "llvm/iTerminators.h"
-#include "llvm/iPHINode.h"
-#include "llvm/Analysis/Dominators.h"
-#include "llvm/Support/CFG.h"
-
-// isCriticalEdge - Return true if the specified edge is a critical edge.
-// Critical edges are edges from a block with multiple successors to a block
-// with multiple predecessors.
-//
-bool isCriticalEdge(const TerminatorInst *TI, unsigned SuccNum) {
- assert(SuccNum < TI->getNumSuccessors() && "Illegal edge specification!");
- if (TI->getNumSuccessors() <= 1) return false;
-
- const BasicBlock *Dest = TI->getSuccessor(SuccNum);
- pred_const_iterator I = pred_begin(Dest), E = pred_end(Dest);
-
- // If there is more than one predecessor, this is a critical edge...
- assert(I != E && "No preds, but we have an edge to the block?");
- ++I; // Skip one edge due to the incoming arc from TI.
- return I != E;
-}
-
-// SplitCriticalEdge - Insert a new node node to split the critical edge. This
-// will update DominatorSet, ImmediateDominator and DominatorTree information if
-// it is available, thus calling this pass will not invalidate either of them.
-//
-void SplitCriticalEdge(TerminatorInst *TI, unsigned SuccNum, Pass *P) {
- assert(isCriticalEdge(TI, SuccNum) &&
- "Cannot break a critical edge, if it isn't a critical edge");
- BasicBlock *TIBB = TI->getParent();
-
- // Create a new basic block, linking it into the CFG.
- BasicBlock *NewBB = new BasicBlock(TIBB->getName()+"_crit_edge");
- BasicBlock *DestBB = TI->getSuccessor(SuccNum);
- // Create our unconditional branch...
- BranchInst *BI = new BranchInst(DestBB);
- NewBB->getInstList().push_back(BI);
-
- // Branch to the new block, breaking the edge...
- TI->setSuccessor(SuccNum, NewBB);
-
- // Insert the block into the function... right after the block TI lives in.
- Function &F = *TIBB->getParent();
- F.getBasicBlockList().insert(TIBB->getNext(), NewBB);
-
- // If there are any PHI nodes in DestBB, we need to update them so that they
- // merge incoming values from NewBB instead of from TIBB.
- //
- for (BasicBlock::iterator I = DestBB->begin();
- PHINode *PN = dyn_cast<PHINode>(&*I); ++I) {
- // We no longer enter through TIBB, now we come in through NewBB.
- PN->replaceUsesOfWith(TIBB, NewBB);
- }
-
- // Now if we have a pass object, update analysis information. Currently we
- // update DominatorSet and DominatorTree information if it's available.
- //
- if (P) {
- // Should we update DominatorSet information?
- if (DominatorSet *DS = P->getAnalysisToUpdate<DominatorSet>()) {
- // The blocks that dominate the new one are the blocks that dominate TIBB
- // plus the new block itself.
- DominatorSet::DomSetType DomSet = DS->getDominators(TIBB);
- DomSet.insert(NewBB); // A block always dominates itself.
- DS->addBasicBlock(NewBB, DomSet);
- }
-
- // Should we update ImmdediateDominator information?
- if (ImmediateDominators *ID =
- P->getAnalysisToUpdate<ImmediateDominators>()) {
- // TIBB is the new immediate dominator for NewBB. NewBB doesn't dominate
- // anything.
- ID->addNewBlock(NewBB, TIBB);
- }
-
- // Should we update DominatorTree information?
- if (DominatorTree *DT = P->getAnalysisToUpdate<DominatorTree>()) {
- DominatorTree::Node *TINode = DT->getNode(TIBB);
-
- // The new block is not the immediate dominator for any other nodes, but
- // TINode is the immediate dominator for the new node.
- //
- DT->createNewNode(NewBB, TINode);
- }
- }
-}