mirror of
https://github.com/c64scene-ar/llvm-6502.git
synced 2024-08-21 03:29:40 +00:00
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@15334 91177308-0d34-0410-b5e6-96231b3b80d8
683 lines
29 KiB
C++
683 lines
29 KiB
C++
//===- PromoteMemoryToRegister.cpp - Convert allocas to registers ---------===//
|
|
//
|
|
// The LLVM Compiler Infrastructure
|
|
//
|
|
// This file was developed by the LLVM research group and is distributed under
|
|
// the University of Illinois Open Source License. See LICENSE.TXT for details.
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
//
|
|
// This file promote memory references to be register references. It promotes
|
|
// alloca instructions which only have loads and stores as uses (or that have
|
|
// PHI nodes which are only loaded from). An alloca is transformed by using
|
|
// dominator frontiers to place PHI nodes, then traversing the function in
|
|
// depth-first order to rewrite loads and stores as appropriate. This is just
|
|
// the standard SSA construction algorithm to construct "pruned" SSA form.
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
#include "llvm/Transforms/Utils/PromoteMemToReg.h"
|
|
#include "llvm/Analysis/Dominators.h"
|
|
#include "llvm/Instructions.h"
|
|
#include "llvm/Function.h"
|
|
#include "llvm/Constant.h"
|
|
#include "llvm/Support/CFG.h"
|
|
#include "llvm/Support/StableBasicBlockNumbering.h"
|
|
#include "Support/StringExtras.h"
|
|
using namespace llvm;
|
|
|
|
/// isAllocaPromotable - Return true if this alloca is legal for promotion.
|
|
/// This is true if there are only loads and stores to the alloca... of if there
|
|
/// is a PHI node using the address which can be trivially transformed.
|
|
///
|
|
bool llvm::isAllocaPromotable(const AllocaInst *AI, const TargetData &TD) {
|
|
// FIXME: If the memory unit is of pointer or integer type, we can permit
|
|
// assignments to subsections of the memory unit.
|
|
|
|
// Only allow direct loads and stores...
|
|
for (Value::use_const_iterator UI = AI->use_begin(), UE = AI->use_end();
|
|
UI != UE; ++UI) // Loop over all of the uses of the alloca
|
|
if (isa<LoadInst>(*UI)) {
|
|
// noop
|
|
} else if (const StoreInst *SI = dyn_cast<StoreInst>(*UI)) {
|
|
if (SI->getOperand(0) == AI)
|
|
return false; // Don't allow a store OF the AI, only INTO the AI.
|
|
} else if (const PHINode *PN = dyn_cast<PHINode>(*UI)) {
|
|
// We only support PHI nodes in a few simple cases. The PHI node is only
|
|
// allowed to have one use, which must be a load instruction, and can only
|
|
// use alloca instructions (no random pointers). Also, there cannot be
|
|
// any accesses to AI between the PHI node and the use of the PHI.
|
|
if (!PN->hasOneUse()) return false;
|
|
|
|
// Our transformation causes the unconditional loading of all pointer
|
|
// operands to the PHI node. Because this could cause a fault if there is
|
|
// a critical edge in the CFG and if one of the pointers is illegal, we
|
|
// refuse to promote PHI nodes unless they are obviously safe. For now,
|
|
// obviously safe means that all of the operands are allocas.
|
|
//
|
|
// If we wanted to extend this code to break critical edges, this
|
|
// restriction could be relaxed, and we could even handle uses of the PHI
|
|
// node that are volatile loads or stores.
|
|
//
|
|
for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
|
|
if (!isa<AllocaInst>(PN->getIncomingValue(i)))
|
|
return false;
|
|
|
|
// Now make sure the one user instruction is in the same basic block as
|
|
// the PHI, and that there are no loads or stores between the PHI node and
|
|
// the access.
|
|
BasicBlock::const_iterator UI = cast<Instruction>(PN->use_back());
|
|
if (!isa<LoadInst>(UI) || cast<LoadInst>(UI)->isVolatile()) return false;
|
|
|
|
// Scan looking for memory accesses.
|
|
// FIXME: this should REALLY use alias analysis.
|
|
for (--UI; !isa<PHINode>(UI); --UI)
|
|
if (isa<LoadInst>(UI) || isa<StoreInst>(UI) || isa<CallInst>(UI))
|
|
return false;
|
|
|
|
// If we got this far, we can promote the PHI use.
|
|
} else if (const SelectInst *SI = dyn_cast<SelectInst>(*UI)) {
|
|
// We only support selects in a few simple cases. The select is only
|
|
// allowed to have one use, which must be a load instruction, and can only
|
|
// use alloca instructions (no random pointers). Also, there cannot be
|
|
// any accesses to AI between the PHI node and the use of the PHI.
|
|
if (!SI->hasOneUse()) return false;
|
|
|
|
// Our transformation causes the unconditional loading of all pointer
|
|
// operands of the select. Because this could cause a fault if there is a
|
|
// critical edge in the CFG and if one of the pointers is illegal, we
|
|
// refuse to promote the select unless it is obviously safe. For now,
|
|
// obviously safe means that all of the operands are allocas.
|
|
//
|
|
if (!isa<AllocaInst>(SI->getOperand(1)) ||
|
|
!isa<AllocaInst>(SI->getOperand(2)))
|
|
return false;
|
|
|
|
// Now make sure the one user instruction is in the same basic block as
|
|
// the PHI, and that there are no loads or stores between the PHI node and
|
|
// the access.
|
|
BasicBlock::const_iterator UI = cast<Instruction>(SI->use_back());
|
|
if (!isa<LoadInst>(UI) || cast<LoadInst>(UI)->isVolatile()) return false;
|
|
|
|
// Scan looking for memory accesses.
|
|
// FIXME: this should REALLY use alias analysis.
|
|
for (--UI; &*UI != SI; --UI)
|
|
if (isa<LoadInst>(UI) || isa<StoreInst>(UI) || isa<CallInst>(UI))
|
|
return false;
|
|
|
|
// If we got this far, we can promote the select use.
|
|
} else {
|
|
return false; // Not a load, store, or promotable PHI?
|
|
}
|
|
|
|
return true;
|
|
}
|
|
|
|
namespace {
|
|
struct PromoteMem2Reg {
|
|
// Allocas - The alloca instructions being promoted
|
|
std::vector<AllocaInst*> Allocas;
|
|
DominatorTree &DT;
|
|
DominanceFrontier &DF;
|
|
const TargetData &TD;
|
|
|
|
// AllocaLookup - Reverse mapping of Allocas
|
|
std::map<AllocaInst*, unsigned> AllocaLookup;
|
|
|
|
// NewPhiNodes - The PhiNodes we're adding.
|
|
std::map<BasicBlock*, std::vector<PHINode*> > NewPhiNodes;
|
|
|
|
// Visited - The set of basic blocks the renamer has already visited.
|
|
std::set<BasicBlock*> Visited;
|
|
|
|
// BBNumbers - Contains a stable numbering of basic blocks to avoid
|
|
// non-determinstic behavior.
|
|
StableBasicBlockNumbering BBNumbers;
|
|
|
|
public:
|
|
PromoteMem2Reg(const std::vector<AllocaInst*> &A, DominatorTree &dt,
|
|
DominanceFrontier &df, const TargetData &td)
|
|
: Allocas(A), DT(dt), DF(df), TD(td) {}
|
|
|
|
void run();
|
|
|
|
private:
|
|
void MarkDominatingPHILive(BasicBlock *BB, unsigned AllocaNum,
|
|
std::set<PHINode*> &DeadPHINodes);
|
|
void PromoteLocallyUsedAlloca(BasicBlock *BB, AllocaInst *AI);
|
|
void PromoteLocallyUsedAllocas(BasicBlock *BB,
|
|
const std::vector<AllocaInst*> &AIs);
|
|
|
|
void RenamePass(BasicBlock *BB, BasicBlock *Pred,
|
|
std::vector<Value*> &IncVals);
|
|
bool QueuePhiNode(BasicBlock *BB, unsigned AllocaIdx, unsigned &Version,
|
|
std::set<PHINode*> &InsertedPHINodes);
|
|
};
|
|
} // end of anonymous namespace
|
|
|
|
void PromoteMem2Reg::run() {
|
|
Function &F = *DF.getRoot()->getParent();
|
|
|
|
// LocallyUsedAllocas - Keep track of all of the alloca instructions which are
|
|
// only used in a single basic block. These instructions can be efficiently
|
|
// promoted by performing a single linear scan over that one block. Since
|
|
// individual basic blocks are sometimes large, we group together all allocas
|
|
// that are live in a single basic block by the basic block they are live in.
|
|
std::map<BasicBlock*, std::vector<AllocaInst*> > LocallyUsedAllocas;
|
|
|
|
|
|
for (unsigned AllocaNum = 0; AllocaNum != Allocas.size(); ++AllocaNum) {
|
|
AllocaInst *AI = Allocas[AllocaNum];
|
|
|
|
assert(isAllocaPromotable(AI, TD) &&
|
|
"Cannot promote non-promotable alloca!");
|
|
assert(AI->getParent()->getParent() == &F &&
|
|
"All allocas should be in the same function, which is same as DF!");
|
|
|
|
if (AI->use_empty()) {
|
|
// If there are no uses of the alloca, just delete it now.
|
|
AI->getParent()->getInstList().erase(AI);
|
|
|
|
// Remove the alloca from the Allocas list, since it has been processed
|
|
Allocas[AllocaNum] = Allocas.back();
|
|
Allocas.pop_back();
|
|
--AllocaNum;
|
|
continue;
|
|
}
|
|
|
|
// Calculate the set of read and write-locations for each alloca. This is
|
|
// analogous to finding the 'uses' and 'definitions' of each variable.
|
|
std::vector<BasicBlock*> DefiningBlocks;
|
|
std::vector<BasicBlock*> UsingBlocks;
|
|
|
|
BasicBlock *OnlyBlock = 0;
|
|
bool OnlyUsedInOneBlock = true;
|
|
|
|
// As we scan the uses of the alloca instruction, keep track of stores, and
|
|
// decide whether all of the loads and stores to the alloca are within the
|
|
// same basic block.
|
|
RestartUseScan:
|
|
for (Value::use_iterator U =AI->use_begin(), E = AI->use_end(); U != E;++U){
|
|
Instruction *User = cast<Instruction>(*U);
|
|
if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
|
|
// Remember the basic blocks which define new values for the alloca
|
|
DefiningBlocks.push_back(SI->getParent());
|
|
} else if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
|
|
// Otherwise it must be a load instruction, keep track of variable reads
|
|
UsingBlocks.push_back(LI->getParent());
|
|
} else if (SelectInst *SI = dyn_cast<SelectInst>(User)) {
|
|
// Because of the restrictions we placed on Select instruction uses
|
|
// above things are very simple. Transform the PHI of addresses into a
|
|
// select of loaded values.
|
|
LoadInst *Load = cast<LoadInst>(SI->use_back());
|
|
std::string LoadName = Load->getName(); Load->setName("");
|
|
|
|
Value *TrueVal = new LoadInst(SI->getOperand(1),
|
|
SI->getOperand(1)->getName()+".val", SI);
|
|
Value *FalseVal = new LoadInst(SI->getOperand(2),
|
|
SI->getOperand(2)->getName()+".val", SI);
|
|
|
|
Value *NewSI = new SelectInst(SI->getOperand(0), TrueVal,
|
|
FalseVal, Load->getName(), SI);
|
|
Load->replaceAllUsesWith(NewSI);
|
|
Load->getParent()->getInstList().erase(Load);
|
|
SI->getParent()->getInstList().erase(SI);
|
|
|
|
// Restart our scan of uses...
|
|
DefiningBlocks.clear();
|
|
UsingBlocks.clear();
|
|
goto RestartUseScan;
|
|
} else {
|
|
// Because of the restrictions we placed on PHI node uses above, the PHI
|
|
// node reads the block in any using predecessors. Transform the PHI of
|
|
// addresses into a PHI of loaded values.
|
|
PHINode *PN = cast<PHINode>(User);
|
|
assert(PN->hasOneUse() && "Cannot handle PHI Node with != 1 use!");
|
|
LoadInst *PNUser = cast<LoadInst>(PN->use_back());
|
|
std::string PNUserName = PNUser->getName(); PNUser->setName("");
|
|
|
|
// Create the new PHI node and insert load instructions as appropriate.
|
|
PHINode *NewPN = new PHINode(AI->getAllocatedType(), PNUserName, PN);
|
|
std::map<BasicBlock*, LoadInst*> NewLoads;
|
|
for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
|
|
BasicBlock *Pred = PN->getIncomingBlock(i);
|
|
LoadInst *&NewLoad = NewLoads[Pred];
|
|
if (NewLoad == 0) // Insert the new load in the predecessor
|
|
NewLoad = new LoadInst(PN->getIncomingValue(i),
|
|
PN->getIncomingValue(i)->getName()+".val",
|
|
Pred->getTerminator());
|
|
NewPN->addIncoming(NewLoad, Pred);
|
|
}
|
|
|
|
// Remove the old load.
|
|
PNUser->replaceAllUsesWith(NewPN);
|
|
PNUser->getParent()->getInstList().erase(PNUser);
|
|
|
|
// Remove the old PHI node.
|
|
PN->getParent()->getInstList().erase(PN);
|
|
|
|
// Restart our scan of uses...
|
|
DefiningBlocks.clear();
|
|
UsingBlocks.clear();
|
|
goto RestartUseScan;
|
|
}
|
|
|
|
if (OnlyUsedInOneBlock) {
|
|
if (OnlyBlock == 0)
|
|
OnlyBlock = User->getParent();
|
|
else if (OnlyBlock != User->getParent())
|
|
OnlyUsedInOneBlock = false;
|
|
}
|
|
}
|
|
|
|
// If the alloca is only read and written in one basic block, just perform a
|
|
// linear sweep over the block to eliminate it.
|
|
if (OnlyUsedInOneBlock) {
|
|
LocallyUsedAllocas[OnlyBlock].push_back(AI);
|
|
|
|
// Remove the alloca from the Allocas list, since it will be processed.
|
|
Allocas[AllocaNum] = Allocas.back();
|
|
Allocas.pop_back();
|
|
--AllocaNum;
|
|
continue;
|
|
}
|
|
|
|
// If we haven't computed a numbering for the BB's in the function, do so
|
|
// now.
|
|
BBNumbers.compute(F);
|
|
|
|
// Compute the locations where PhiNodes need to be inserted. Look at the
|
|
// dominance frontier of EACH basic-block we have a write in.
|
|
//
|
|
unsigned CurrentVersion = 0;
|
|
std::set<PHINode*> InsertedPHINodes;
|
|
std::vector<unsigned> DFBlocks;
|
|
while (!DefiningBlocks.empty()) {
|
|
BasicBlock *BB = DefiningBlocks.back();
|
|
DefiningBlocks.pop_back();
|
|
|
|
// Look up the DF for this write, add it to PhiNodes
|
|
DominanceFrontier::const_iterator it = DF.find(BB);
|
|
if (it != DF.end()) {
|
|
const DominanceFrontier::DomSetType &S = it->second;
|
|
|
|
// In theory we don't need the indirection through the DFBlocks vector.
|
|
// In practice, the order of calling QueuePhiNode would depend on the
|
|
// (unspecified) ordering of basic blocks in the dominance frontier,
|
|
// which would give PHI nodes non-determinstic subscripts. Fix this by
|
|
// processing blocks in order of the occurance in the function.
|
|
for (DominanceFrontier::DomSetType::iterator P = S.begin(),PE = S.end();
|
|
P != PE; ++P)
|
|
DFBlocks.push_back(BBNumbers.getNumber(*P));
|
|
|
|
// Sort by which the block ordering in the function.
|
|
std::sort(DFBlocks.begin(), DFBlocks.end());
|
|
|
|
for (unsigned i = 0, e = DFBlocks.size(); i != e; ++i) {
|
|
BasicBlock *BB = BBNumbers.getBlock(DFBlocks[i]);
|
|
if (QueuePhiNode(BB, AllocaNum, CurrentVersion, InsertedPHINodes))
|
|
DefiningBlocks.push_back(BB);
|
|
}
|
|
DFBlocks.clear();
|
|
}
|
|
}
|
|
|
|
// Now that we have inserted PHI nodes along the Iterated Dominance Frontier
|
|
// of the writes to the variable, scan through the reads of the variable,
|
|
// marking PHI nodes which are actually necessary as alive (by removing them
|
|
// from the InsertedPHINodes set). This is not perfect: there may PHI
|
|
// marked alive because of loads which are dominated by stores, but there
|
|
// will be no unmarked PHI nodes which are actually used.
|
|
//
|
|
for (unsigned i = 0, e = UsingBlocks.size(); i != e; ++i)
|
|
MarkDominatingPHILive(UsingBlocks[i], AllocaNum, InsertedPHINodes);
|
|
UsingBlocks.clear();
|
|
|
|
// If there are any PHI nodes which are now known to be dead, remove them!
|
|
for (std::set<PHINode*>::iterator I = InsertedPHINodes.begin(),
|
|
E = InsertedPHINodes.end(); I != E; ++I) {
|
|
PHINode *PN = *I;
|
|
std::vector<PHINode*> &BBPNs = NewPhiNodes[PN->getParent()];
|
|
BBPNs[AllocaNum] = 0;
|
|
|
|
// Check to see if we just removed the last inserted PHI node from this
|
|
// basic block. If so, remove the entry for the basic block.
|
|
bool HasOtherPHIs = false;
|
|
for (unsigned i = 0, e = BBPNs.size(); i != e; ++i)
|
|
if (BBPNs[i]) {
|
|
HasOtherPHIs = true;
|
|
break;
|
|
}
|
|
if (!HasOtherPHIs)
|
|
NewPhiNodes.erase(PN->getParent());
|
|
|
|
PN->getParent()->getInstList().erase(PN);
|
|
}
|
|
|
|
// Keep the reverse mapping of the 'Allocas' array.
|
|
AllocaLookup[Allocas[AllocaNum]] = AllocaNum;
|
|
}
|
|
|
|
// Process all allocas which are only used in a single basic block.
|
|
for (std::map<BasicBlock*, std::vector<AllocaInst*> >::iterator I =
|
|
LocallyUsedAllocas.begin(), E = LocallyUsedAllocas.end(); I != E; ++I){
|
|
const std::vector<AllocaInst*> &Allocas = I->second;
|
|
assert(!Allocas.empty() && "empty alloca list??");
|
|
|
|
// It's common for there to only be one alloca in the list. Handle it
|
|
// efficiently.
|
|
if (Allocas.size() == 1)
|
|
PromoteLocallyUsedAlloca(I->first, Allocas[0]);
|
|
else
|
|
PromoteLocallyUsedAllocas(I->first, Allocas);
|
|
}
|
|
|
|
if (Allocas.empty())
|
|
return; // All of the allocas must have been trivial!
|
|
|
|
// Set the incoming values for the basic block to be null values for all of
|
|
// the alloca's. We do this in case there is a load of a value that has not
|
|
// been stored yet. In this case, it will get this null value.
|
|
//
|
|
std::vector<Value *> Values(Allocas.size());
|
|
for (unsigned i = 0, e = Allocas.size(); i != e; ++i)
|
|
Values[i] = Constant::getNullValue(Allocas[i]->getAllocatedType());
|
|
|
|
// Walks all basic blocks in the function performing the SSA rename algorithm
|
|
// and inserting the phi nodes we marked as necessary
|
|
//
|
|
RenamePass(F.begin(), 0, Values);
|
|
|
|
// The renamer uses the Visited set to avoid infinite loops. Clear it now.
|
|
Visited.clear();
|
|
|
|
// Remove the allocas themselves from the function...
|
|
for (unsigned i = 0, e = Allocas.size(); i != e; ++i) {
|
|
Instruction *A = Allocas[i];
|
|
|
|
// If there are any uses of the alloca instructions left, they must be in
|
|
// sections of dead code that were not processed on the dominance frontier.
|
|
// Just delete the users now.
|
|
//
|
|
if (!A->use_empty())
|
|
A->replaceAllUsesWith(Constant::getNullValue(A->getType()));
|
|
A->getParent()->getInstList().erase(A);
|
|
}
|
|
|
|
// At this point, the renamer has added entries to PHI nodes for all reachable
|
|
// code. Unfortunately, there may be blocks which are not reachable, which
|
|
// the renamer hasn't traversed. If this is the case, the PHI nodes may not
|
|
// have incoming values for all predecessors. Loop over all PHI nodes we have
|
|
// created, inserting null constants if they are missing any incoming values.
|
|
//
|
|
for (std::map<BasicBlock*, std::vector<PHINode *> >::iterator I =
|
|
NewPhiNodes.begin(), E = NewPhiNodes.end(); I != E; ++I) {
|
|
|
|
std::vector<BasicBlock*> Preds(pred_begin(I->first), pred_end(I->first));
|
|
std::vector<PHINode*> &PNs = I->second;
|
|
assert(!PNs.empty() && "Empty PHI node list??");
|
|
|
|
// Only do work here if there the PHI nodes are missing incoming values. We
|
|
// know that all PHI nodes that were inserted in a block will have the same
|
|
// number of incoming values, so we can just check any PHI node.
|
|
PHINode *FirstPHI;
|
|
for (unsigned i = 0; (FirstPHI = PNs[i]) == 0; ++i)
|
|
/*empty*/;
|
|
|
|
if (Preds.size() != FirstPHI->getNumIncomingValues()) {
|
|
// Ok, now we know that all of the PHI nodes are missing entries for some
|
|
// basic blocks. Start by sorting the incoming predecessors for efficient
|
|
// access.
|
|
std::sort(Preds.begin(), Preds.end());
|
|
|
|
// Now we loop through all BB's which have entries in FirstPHI and remove
|
|
// them from the Preds list.
|
|
for (unsigned i = 0, e = FirstPHI->getNumIncomingValues(); i != e; ++i) {
|
|
// Do a log(n) search of the Preds list for the entry we want.
|
|
std::vector<BasicBlock*>::iterator EntIt =
|
|
std::lower_bound(Preds.begin(), Preds.end(),
|
|
FirstPHI->getIncomingBlock(i));
|
|
assert(EntIt != Preds.end() && *EntIt == FirstPHI->getIncomingBlock(i)&&
|
|
"PHI node has entry for a block which is not a predecessor!");
|
|
|
|
// Remove the entry
|
|
Preds.erase(EntIt);
|
|
}
|
|
|
|
// At this point, the blocks left in the preds list must have dummy
|
|
// entries inserted into every PHI nodes for the block.
|
|
for (unsigned i = 0, e = PNs.size(); i != e; ++i)
|
|
if (PHINode *PN = PNs[i]) {
|
|
Value *NullVal = Constant::getNullValue(PN->getType());
|
|
for (unsigned pred = 0, e = Preds.size(); pred != e; ++pred)
|
|
PN->addIncoming(NullVal, Preds[pred]);
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
// MarkDominatingPHILive - Mem2Reg wants to construct "pruned" SSA form, not
|
|
// "minimal" SSA form. To do this, it inserts all of the PHI nodes on the IDF
|
|
// as usual (inserting the PHI nodes in the DeadPHINodes set), then processes
|
|
// each read of the variable. For each block that reads the variable, this
|
|
// function is called, which removes used PHI nodes from the DeadPHINodes set.
|
|
// After all of the reads have been processed, any PHI nodes left in the
|
|
// DeadPHINodes set are removed.
|
|
//
|
|
void PromoteMem2Reg::MarkDominatingPHILive(BasicBlock *BB, unsigned AllocaNum,
|
|
std::set<PHINode*> &DeadPHINodes) {
|
|
// Scan the immediate dominators of this block looking for a block which has a
|
|
// PHI node for Alloca num. If we find it, mark the PHI node as being alive!
|
|
for (DominatorTree::Node *N = DT[BB]; N; N = N->getIDom()) {
|
|
BasicBlock *DomBB = N->getBlock();
|
|
std::map<BasicBlock*, std::vector<PHINode*> >::iterator
|
|
I = NewPhiNodes.find(DomBB);
|
|
if (I != NewPhiNodes.end() && I->second[AllocaNum]) {
|
|
// Ok, we found an inserted PHI node which dominates this value.
|
|
PHINode *DominatingPHI = I->second[AllocaNum];
|
|
|
|
// Find out if we previously thought it was dead.
|
|
std::set<PHINode*>::iterator DPNI = DeadPHINodes.find(DominatingPHI);
|
|
if (DPNI != DeadPHINodes.end()) {
|
|
// Ok, until now, we thought this PHI node was dead. Mark it as being
|
|
// alive/needed.
|
|
DeadPHINodes.erase(DPNI);
|
|
|
|
// Now that we have marked the PHI node alive, also mark any PHI nodes
|
|
// which it might use as being alive as well.
|
|
for (pred_iterator PI = pred_begin(DomBB), PE = pred_end(DomBB);
|
|
PI != PE; ++PI)
|
|
MarkDominatingPHILive(*PI, AllocaNum, DeadPHINodes);
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
/// PromoteLocallyUsedAlloca - Many allocas are only used within a single basic
|
|
/// block. If this is the case, avoid traversing the CFG and inserting a lot of
|
|
/// potentially useless PHI nodes by just performing a single linear pass over
|
|
/// the basic block using the Alloca.
|
|
///
|
|
void PromoteMem2Reg::PromoteLocallyUsedAlloca(BasicBlock *BB, AllocaInst *AI) {
|
|
assert(!AI->use_empty() && "There are no uses of the alloca!");
|
|
|
|
// Handle degenerate cases quickly.
|
|
if (AI->hasOneUse()) {
|
|
Instruction *U = cast<Instruction>(AI->use_back());
|
|
if (LoadInst *LI = dyn_cast<LoadInst>(U)) {
|
|
// Must be a load of uninitialized value.
|
|
LI->replaceAllUsesWith(Constant::getNullValue(AI->getAllocatedType()));
|
|
} else {
|
|
// Otherwise it must be a store which is never read.
|
|
assert(isa<StoreInst>(U));
|
|
}
|
|
BB->getInstList().erase(U);
|
|
} else {
|
|
// Uses of the uninitialized memory location shall get zero...
|
|
Value *CurVal = Constant::getNullValue(AI->getAllocatedType());
|
|
|
|
for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ) {
|
|
Instruction *Inst = I++;
|
|
if (LoadInst *LI = dyn_cast<LoadInst>(Inst)) {
|
|
if (LI->getOperand(0) == AI) {
|
|
// Loads just returns the "current value"...
|
|
LI->replaceAllUsesWith(CurVal);
|
|
BB->getInstList().erase(LI);
|
|
}
|
|
} else if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
|
|
if (SI->getOperand(1) == AI) {
|
|
// Store updates the "current value"...
|
|
CurVal = SI->getOperand(0);
|
|
BB->getInstList().erase(SI);
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
// After traversing the basic block, there should be no more uses of the
|
|
// alloca, remove it now.
|
|
assert(AI->use_empty() && "Uses of alloca from more than one BB??");
|
|
AI->getParent()->getInstList().erase(AI);
|
|
}
|
|
|
|
/// PromoteLocallyUsedAllocas - This method is just like
|
|
/// PromoteLocallyUsedAlloca, except that it processes multiple alloca
|
|
/// instructions in parallel. This is important in cases where we have large
|
|
/// basic blocks, as we don't want to rescan the entire basic block for each
|
|
/// alloca which is locally used in it (which might be a lot).
|
|
void PromoteMem2Reg::
|
|
PromoteLocallyUsedAllocas(BasicBlock *BB, const std::vector<AllocaInst*> &AIs) {
|
|
std::map<AllocaInst*, Value*> CurValues;
|
|
for (unsigned i = 0, e = AIs.size(); i != e; ++i)
|
|
CurValues[AIs[i]] = 0; // Insert with null value
|
|
|
|
for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ) {
|
|
Instruction *Inst = I++;
|
|
if (LoadInst *LI = dyn_cast<LoadInst>(Inst)) {
|
|
// Is this a load of an alloca we are tracking?
|
|
if (AllocaInst *AI = dyn_cast<AllocaInst>(LI->getOperand(0))) {
|
|
std::map<AllocaInst*, Value*>::iterator AIt = CurValues.find(AI);
|
|
if (AIt != CurValues.end()) {
|
|
// Loads just returns the "current value"...
|
|
if (AIt->second == 0) // Uninitialized value??
|
|
AIt->second =Constant::getNullValue(AIt->first->getAllocatedType());
|
|
LI->replaceAllUsesWith(AIt->second);
|
|
BB->getInstList().erase(LI);
|
|
}
|
|
}
|
|
} else if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
|
|
if (AllocaInst *AI = dyn_cast<AllocaInst>(SI->getOperand(1))) {
|
|
std::map<AllocaInst*, Value*>::iterator AIt = CurValues.find(AI);
|
|
if (AIt != CurValues.end()) {
|
|
// Store updates the "current value"...
|
|
AIt->second = SI->getOperand(0);
|
|
BB->getInstList().erase(SI);
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
|
|
|
|
// QueuePhiNode - queues a phi-node to be added to a basic-block for a specific
|
|
// Alloca returns true if there wasn't already a phi-node for that variable
|
|
//
|
|
bool PromoteMem2Reg::QueuePhiNode(BasicBlock *BB, unsigned AllocaNo,
|
|
unsigned &Version,
|
|
std::set<PHINode*> &InsertedPHINodes) {
|
|
// Look up the basic-block in question
|
|
std::vector<PHINode*> &BBPNs = NewPhiNodes[BB];
|
|
if (BBPNs.empty()) BBPNs.resize(Allocas.size());
|
|
|
|
// If the BB already has a phi node added for the i'th alloca then we're done!
|
|
if (BBPNs[AllocaNo]) return false;
|
|
|
|
// Create a PhiNode using the dereferenced type... and add the phi-node to the
|
|
// BasicBlock.
|
|
BBPNs[AllocaNo] = new PHINode(Allocas[AllocaNo]->getAllocatedType(),
|
|
Allocas[AllocaNo]->getName() + "." +
|
|
utostr(Version++), BB->begin());
|
|
InsertedPHINodes.insert(BBPNs[AllocaNo]);
|
|
return true;
|
|
}
|
|
|
|
|
|
// RenamePass - Recursively traverse the CFG of the function, renaming loads and
|
|
// stores to the allocas which we are promoting. IncomingVals indicates what
|
|
// value each Alloca contains on exit from the predecessor block Pred.
|
|
//
|
|
void PromoteMem2Reg::RenamePass(BasicBlock *BB, BasicBlock *Pred,
|
|
std::vector<Value*> &IncomingVals) {
|
|
|
|
// If this BB needs a PHI node, update the PHI node for each variable we need
|
|
// PHI nodes for.
|
|
std::map<BasicBlock*, std::vector<PHINode *> >::iterator
|
|
BBPNI = NewPhiNodes.find(BB);
|
|
if (BBPNI != NewPhiNodes.end()) {
|
|
std::vector<PHINode *> &BBPNs = BBPNI->second;
|
|
for (unsigned k = 0; k != BBPNs.size(); ++k)
|
|
if (PHINode *PN = BBPNs[k]) {
|
|
// Add this incoming value to the PHI node.
|
|
PN->addIncoming(IncomingVals[k], Pred);
|
|
|
|
// The currently active variable for this block is now the PHI.
|
|
IncomingVals[k] = PN;
|
|
}
|
|
}
|
|
|
|
// don't revisit nodes
|
|
if (Visited.count(BB)) return;
|
|
|
|
// mark as visited
|
|
Visited.insert(BB);
|
|
|
|
for (BasicBlock::iterator II = BB->begin(); !isa<TerminatorInst>(II); ) {
|
|
Instruction *I = II++; // get the instruction, increment iterator
|
|
|
|
if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
|
|
if (AllocaInst *Src = dyn_cast<AllocaInst>(LI->getPointerOperand())) {
|
|
std::map<AllocaInst*, unsigned>::iterator AI = AllocaLookup.find(Src);
|
|
if (AI != AllocaLookup.end()) {
|
|
Value *V = IncomingVals[AI->second];
|
|
|
|
// walk the use list of this load and replace all uses with r
|
|
LI->replaceAllUsesWith(V);
|
|
BB->getInstList().erase(LI);
|
|
}
|
|
}
|
|
} else if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
|
|
// Delete this instruction and mark the name as the current holder of the
|
|
// value
|
|
if (AllocaInst *Dest = dyn_cast<AllocaInst>(SI->getPointerOperand())) {
|
|
std::map<AllocaInst *, unsigned>::iterator ai = AllocaLookup.find(Dest);
|
|
if (ai != AllocaLookup.end()) {
|
|
// what value were we writing?
|
|
IncomingVals[ai->second] = SI->getOperand(0);
|
|
BB->getInstList().erase(SI);
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
// Recurse to our successors.
|
|
TerminatorInst *TI = BB->getTerminator();
|
|
for (unsigned i = 0; i != TI->getNumSuccessors(); i++) {
|
|
std::vector<Value*> OutgoingVals(IncomingVals);
|
|
RenamePass(TI->getSuccessor(i), BB, OutgoingVals);
|
|
}
|
|
}
|
|
|
|
/// PromoteMemToReg - Promote the specified list of alloca instructions into
|
|
/// scalar registers, inserting PHI nodes as appropriate. This function makes
|
|
/// use of DominanceFrontier information. This function does not modify the CFG
|
|
/// of the function at all. All allocas must be from the same function.
|
|
///
|
|
void llvm::PromoteMemToReg(const std::vector<AllocaInst*> &Allocas,
|
|
DominatorTree &DT, DominanceFrontier &DF,
|
|
const TargetData &TD) {
|
|
// If there is nothing to do, bail out...
|
|
if (Allocas.empty()) return;
|
|
PromoteMem2Reg(Allocas, DT, DF, TD).run();
|
|
}
|