+/// RewriteForPHI - Helper for Rewrite. PHI nodes are special because the use
+/// of their operands effectively happens in their predecessor blocks, so the
+/// expression may need to be expanded in multiple places.
+void LSRInstance::RewriteForPHI(PHINode *PN,
+ const LSRFixup &LF,
+ const Formula &F,
+ SCEVExpander &Rewriter,
+ SmallVectorImpl<WeakVH> &DeadInsts,
+ Pass *P) const {
+ DenseMap<BasicBlock *, Value *> Inserted;
+ for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
+ if (PN->getIncomingValue(i) == LF.OperandValToReplace) {
+ BasicBlock *BB = PN->getIncomingBlock(i);
+
+ // If this is a critical edge, split the edge so that we do not insert
+ // the code on all predecessor/successor paths. We do this unless this
+ // is the canonical backedge for this loop, which complicates post-inc
+ // users.
+ if (e != 1 && BB->getTerminator()->getNumSuccessors() > 1 &&
+ !isa<IndirectBrInst>(BB->getTerminator()) &&
+ (PN->getParent() != L->getHeader() || !L->contains(BB))) {
+ // Split the critical edge.
+ BasicBlock *NewBB = SplitCriticalEdge(BB, PN->getParent(), P);
+
+ // If PN is outside of the loop and BB is in the loop, we want to
+ // move the block to be immediately before the PHI block, not
+ // immediately after BB.
+ if (L->contains(BB) && !L->contains(PN))
+ NewBB->moveBefore(PN->getParent());
+
+ // Splitting the edge can reduce the number of PHI entries we have.
+ e = PN->getNumIncomingValues();
+ BB = NewBB;
+ i = PN->getBasicBlockIndex(BB);
+ }
+
+ std::pair<DenseMap<BasicBlock *, Value *>::iterator, bool> Pair =
+ Inserted.insert(std::make_pair(BB, static_cast<Value *>(0)));
+ if (!Pair.second)
+ PN->setIncomingValue(i, Pair.first->second);
+ else {
+ Value *FullV = Expand(LF, F, BB->getTerminator(), Rewriter, DeadInsts);
+
+ // If this is reuse-by-noop-cast, insert the noop cast.
+ const Type *OpTy = LF.OperandValToReplace->getType();
+ if (FullV->getType() != OpTy)
+ FullV =
+ CastInst::Create(CastInst::getCastOpcode(FullV, false,
+ OpTy, false),
+ FullV, LF.OperandValToReplace->getType(),
+ "tmp", BB->getTerminator());
+
+ PN->setIncomingValue(i, FullV);
+ Pair.first->second = FullV;
+ }
+ }
+}
+