diff options
| -rw-r--r-- | llvm/lib/Transforms/Utils/DemoteRegToStack.cpp | 38 |
1 files changed, 17 insertions, 21 deletions
diff --git a/llvm/lib/Transforms/Utils/DemoteRegToStack.cpp b/llvm/lib/Transforms/Utils/DemoteRegToStack.cpp index 3ef6b018bf8..c2483ab43c9 100644 --- a/llvm/lib/Transforms/Utils/DemoteRegToStack.cpp +++ b/llvm/lib/Transforms/Utils/DemoteRegToStack.cpp @@ -28,7 +28,6 @@ using namespace llvm; /// alloca. This allows the CFG to be changed around without fear of /// invalidating the SSA information for the value. It returns the pointer to /// the alloca inserted to create a stack slot for I. -/// AllocaInst* llvm::DemoteRegToStack(Instruction &I, bool VolatileLoads, Instruction *AllocaPoint) { if (I.use_empty()) { @@ -47,20 +46,19 @@ AllocaInst* llvm::DemoteRegToStack(Instruction &I, bool VolatileLoads, F->getEntryBlock().begin()); } - // Change all of the users of the instruction to read from the stack slot - // instead. + // Change all of the users of the instruction to read from the stack slot. while (!I.use_empty()) { Instruction *U = cast<Instruction>(I.use_back()); if (PHINode *PN = dyn_cast<PHINode>(U)) { // If this is a PHI node, we can't insert a load of the value before the - // use. Instead, insert the load in the predecessor block corresponding + // use. Instead insert the load in the predecessor block corresponding // to the incoming value. // // Note that if there are multiple edges from a basic block to this PHI - // node that we cannot multiple loads. The problem is that the resultant - // PHI node will have multiple values (from each load) coming in from the - // same block, which is illegal SSA form. For this reason, we keep track - // and reuse loads we insert. + // node that we cannot have multiple loads. The problem is that the + // resulting PHI node will have multiple values (from each load) coming in + // from the same block, which is illegal SSA form. For this reason, we + // keep track of and reuse loads we insert. std::map<BasicBlock*, Value*> Loads; for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) if (PN->getIncomingValue(i) == &I) { @@ -81,9 +79,9 @@ AllocaInst* llvm::DemoteRegToStack(Instruction &I, bool VolatileLoads, } - // Insert stores of the computed value into the stack slot. We have to be - // careful is I is an invoke instruction though, because we can't insert the - // store AFTER the terminator instruction. + // Insert stores of the computed value into the stack slot. We have to be + // careful if I is an invoke instruction, because we can't insert the store + // AFTER the terminator instruction. BasicBlock::iterator InsertPt; if (!isa<TerminatorInst>(I)) { InsertPt = &I; @@ -98,16 +96,15 @@ AllocaInst* llvm::DemoteRegToStack(Instruction &I, bool VolatileLoads, } for (; isa<PHINode>(InsertPt) || isa<LandingPadInst>(InsertPt); ++InsertPt) - /* empty */; // Don't insert before any PHI nodes or landingpad instrs. - new StoreInst(&I, Slot, InsertPt); + /* empty */; // Don't insert before PHI nodes or landingpad instrs. + new StoreInst(&I, Slot, InsertPt); return Slot; } - -/// DemotePHIToStack - This function takes a virtual register computed by a phi -/// node and replaces it with a slot in the stack frame, allocated via alloca. -/// The phi node is deleted and it returns the pointer to the alloca inserted. +/// DemotePHIToStack - This function takes a virtual register computed by a PHI +/// node and replaces it with a slot in the stack frame allocated via alloca. +/// The PHI node is deleted. It returns the pointer to the alloca inserted. AllocaInst* llvm::DemotePHIToStack(PHINode *P, Instruction *AllocaPoint) { if (P->use_empty()) { P->eraseFromParent(); @@ -125,7 +122,7 @@ AllocaInst* llvm::DemotePHIToStack(PHINode *P, Instruction *AllocaPoint) { F->getEntryBlock().begin()); } - // Iterate over each operand, insert store in each predecessor. + // Iterate over each operand inserting a store in each predecessor. for (unsigned i = 0, e = P->getNumIncomingValues(); i < e; ++i) { if (InvokeInst *II = dyn_cast<InvokeInst>(P->getIncomingValue(i))) { assert(II->getParent() != P->getIncomingBlock(i) && @@ -135,12 +132,11 @@ AllocaInst* llvm::DemotePHIToStack(PHINode *P, Instruction *AllocaPoint) { P->getIncomingBlock(i)->getTerminator()); } - // Insert load in place of the phi and replace all uses. + // Insert a load in place of the PHI and replace all uses. Value *V = new LoadInst(Slot, P->getName()+".reload", P); P->replaceAllUsesWith(V); - // Delete phi. + // Delete PHI. P->eraseFromParent(); - return Slot; } |
