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Combine the implementations of the core part of the SSAUpdater and

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MachineSSAUpdater to avoid duplicating all the code.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@103060 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Bob Wilson
2010-05-04 23:18:19 +00:00
parent d2760d1cba
commit 4aad88d1fd
5 changed files with 707 additions and 927 deletions
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559
lib/Transforms/Utils/SSAUpdater.cpp
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@@ -12,7 +12,6 @@
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "ssaupdater"
#include "llvm/Transforms/Utils/SSAUpdater.h"
#include "llvm/Instructions.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/Support/AlignOf.h"
@@ -20,40 +19,17 @@
#include "llvm/Support/CFG.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Transforms/Utils/SSAUpdater.h"
#include "llvm/Transforms/Utils/SSAUpdaterImpl.h"
using namespace llvm;
/// BBInfo - Per-basic block information used internally by SSAUpdater.
/// The predecessors of each block are cached here since pred_iterator is
/// slow and we need to iterate over the blocks at least a few times.
class SSAUpdater::BBInfo {
public:
BasicBlock *BB; // Back-pointer to the corresponding block.
Value *AvailableVal; // Value to use in this block.
BBInfo *DefBB; // Block that defines the available value.
int BlkNum; // Postorder number.
BBInfo *IDom; // Immediate dominator.
unsigned NumPreds; // Number of predecessor blocks.
BBInfo **Preds; // Array[NumPreds] of predecessor blocks.
PHINode *PHITag; // Marker for existing PHIs that match.
BBInfo(BasicBlock *ThisBB, Value *V)
: BB(ThisBB), AvailableVal(V), DefBB(V ? this : 0), BlkNum(0), IDom(0),
NumPreds(0), Preds(0), PHITag(0) { }
};
typedef DenseMap<BasicBlock*, SSAUpdater::BBInfo*> BBMapTy;
typedef DenseMap<BasicBlock*, Value*> AvailableValsTy;
static AvailableValsTy &getAvailableVals(void *AV) {
return *static_cast<AvailableValsTy*>(AV);
}
static BBMapTy *getBBMap(void *BM) {
return static_cast<BBMapTy*>(BM);
}
SSAUpdater::SSAUpdater(SmallVectorImpl<PHINode*> *NewPHI)
: AV(0), PrototypeValue(0), BM(0), InsertedPHIs(NewPHI) {}
: AV(0), PrototypeValue(0), InsertedPHIs(NewPHI) {}
SSAUpdater::~SSAUpdater() {
delete &getAvailableVals(AV);
@@ -105,9 +81,7 @@ static bool IsEquivalentPHI(PHINode *PHI,
/// GetValueAtEndOfBlock - Construct SSA form, materializing a value that is
/// live at the end of the specified block.
Value *SSAUpdater::GetValueAtEndOfBlock(BasicBlock *BB) {
assert(BM == 0 && "Unexpected Internal State");
Value *Res = GetValueAtEndOfBlockInternal(BB);
assert(BM == 0 && "Unexpected Internal State");
return Res;
}
@@ -231,6 +205,117 @@ void SSAUpdater::RewriteUse(Use &U) {
U.set(V);
}
/// PHIiter - Iterator for PHI operands. This is used for the PHI_iterator
/// in the SSAUpdaterImpl template.
namespace {
class PHIiter {
private:
PHINode *PHI;
unsigned idx;
public:
explicit PHIiter(PHINode *P) // begin iterator
: PHI(P), idx(0) {}
PHIiter(PHINode *P, bool) // end iterator
: PHI(P), idx(PHI->getNumIncomingValues()) {}
PHIiter &operator++() { ++idx; return *this; }
bool operator==(const PHIiter& x) const { return idx == x.idx; }
bool operator!=(const PHIiter& x) const { return !operator==(x); }
Value *getIncomingValue() { return PHI->getIncomingValue(idx); }
BasicBlock *getIncomingBlock() { return PHI->getIncomingBlock(idx); }
};
}
/// SSAUpdaterTraits<SSAUpdater> - Traits for the SSAUpdaterImpl template,
/// specialized for SSAUpdater.
namespace llvm {
template<>
class SSAUpdaterTraits<SSAUpdater> {
public:
typedef BasicBlock BlkT;
typedef Value *ValT;
typedef PHINode PhiT;
typedef succ_iterator BlkSucc_iterator;
static BlkSucc_iterator BlkSucc_begin(BlkT *BB) { return succ_begin(BB); }
static BlkSucc_iterator BlkSucc_end(BlkT *BB) { return succ_end(BB); }
typedef PHIiter PHI_iterator;
static inline PHI_iterator PHI_begin(PhiT *PHI) { return PHI_iterator(PHI); }
static inline PHI_iterator PHI_end(PhiT *PHI) {
return PHI_iterator(PHI, true);
}
/// FindPredecessorBlocks - Put the predecessors of Info->BB into the Preds
/// vector, set Info->NumPreds, and allocate space in Info->Preds.
static void FindPredecessorBlocks(BasicBlock *BB,
SmallVectorImpl<BasicBlock*> *Preds) {
// We can get our predecessor info by walking the pred_iterator list,
// but it is relatively slow. If we already have PHI nodes in this
// block, walk one of them to get the predecessor list instead.
if (PHINode *SomePhi = dyn_cast<PHINode>(BB->begin())) {
for (unsigned PI = 0, E = SomePhi->getNumIncomingValues(); PI != E; ++PI)
Preds->push_back(SomePhi->getIncomingBlock(PI));
} else {
for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI)
Preds->push_back(*PI);
}
}
/// GetUndefVal - Get an undefined value of the same type as the value
/// being handled.
static Value *GetUndefVal(BasicBlock *BB, SSAUpdater *Updater) {
return UndefValue::get(Updater->PrototypeValue->getType());
}
/// CreateEmptyPHI - Create a new PHI instruction in the specified block.
/// Reserve space for the operands but do not fill them in yet.
static Value *CreateEmptyPHI(BasicBlock *BB, unsigned NumPreds,
SSAUpdater *Updater) {
PHINode *PHI = PHINode::Create(Updater->PrototypeValue->getType(),
Updater->PrototypeValue->getName(),
&BB->front());
PHI->reserveOperandSpace(NumPreds);
return PHI;
}
/// AddPHIOperand - Add the specified value as an operand of the PHI for
/// the specified predecessor block.
static void AddPHIOperand(PHINode *PHI, Value *Val, BasicBlock *Pred) {
PHI->addIncoming(Val, Pred);
}
/// InstrIsPHI - Check if an instruction is a PHI.
///
static PHINode *InstrIsPHI(Instruction *I) {
return dyn_cast<PHINode>(I);
}
/// ValueIsPHI - Check if a value is a PHI.
///
static PHINode *ValueIsPHI(Value *Val, SSAUpdater *Updater) {
return dyn_cast<PHINode>(Val);
}
/// ValueIsNewPHI - Like ValueIsPHI but also check if the PHI has no source
/// operands, i.e., it was just added.
static PHINode *ValueIsNewPHI(Value *Val, SSAUpdater *Updater) {
PHINode *PHI = ValueIsPHI(Val, Updater);
if (PHI && PHI->getNumIncomingValues() == 0)
return PHI;
return 0;
}
/// GetPHIValue - For the specified PHI instruction, return the value
/// that it defines.
static Value *GetPHIValue(PHINode *PHI) {
return PHI;
}
};
} // End llvm namespace
/// GetValueAtEndOfBlockInternal - Check to see if AvailableVals has an entry
/// for the specified BB and if so, return it. If not, construct SSA form by
/// first calculating the required placement of PHIs and then inserting new
@@ -240,418 +325,6 @@ Value *SSAUpdater::GetValueAtEndOfBlockInternal(BasicBlock *BB) {
if (Value *V = AvailableVals[BB])
return V;
// Pool allocation used internally by GetValueAtEndOfBlock.
BumpPtrAllocator Allocator;
BBMapTy BBMapObj;
BM = &BBMapObj;
SmallVector<BBInfo*, 100> BlockList;
BuildBlockList(BB, &BlockList, &Allocator);
// Special case: bail out if BB is unreachable.
if (BlockList.size() == 0) {
BM = 0;
return UndefValue::get(PrototypeValue->getType());
}
FindDominators(&BlockList);
FindPHIPlacement(&BlockList);
FindAvailableVals(&BlockList);
BM = 0;
return BBMapObj[BB]->DefBB->AvailableVal;
}
/// FindPredecessorBlocks - Put the predecessors of Info->BB into the Preds
/// vector, set Info->NumPreds, and allocate space in Info->Preds.
static void FindPredecessorBlocks(SSAUpdater::BBInfo *Info,
SmallVectorImpl<BasicBlock*> *Preds,
BumpPtrAllocator *Allocator) {
// We can get our predecessor info by walking the pred_iterator list,
// but it is relatively slow. If we already have PHI nodes in this
// block, walk one of them to get the predecessor list instead.
BasicBlock *BB = Info->BB;
if (PHINode *SomePhi = dyn_cast<PHINode>(BB->begin())) {
for (unsigned PI = 0, E = SomePhi->getNumIncomingValues(); PI != E; ++PI)
Preds->push_back(SomePhi->getIncomingBlock(PI));
} else {
for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI)
Preds->push_back(*PI);
}
Info->NumPreds = Preds->size();
Info->Preds = static_cast<SSAUpdater::BBInfo**>
(Allocator->Allocate(Info->NumPreds * sizeof(SSAUpdater::BBInfo*),
AlignOf<SSAUpdater::BBInfo*>::Alignment));
}
/// BuildBlockList - Starting from the specified basic block, traverse back
/// through its predecessors until reaching blocks with known values. Create
/// BBInfo structures for the blocks and append them to the block list.
void SSAUpdater::BuildBlockList(BasicBlock *BB, BlockListTy *BlockList,
BumpPtrAllocator *Allocator) {
AvailableValsTy &AvailableVals = getAvailableVals(AV);
BBMapTy *BBMap = getBBMap(BM);
SmallVector<BBInfo*, 10> RootList;
SmallVector<BBInfo*, 64> WorkList;
BBInfo *Info = new (*Allocator) BBInfo(BB, 0);
(*BBMap)[BB] = Info;
WorkList.push_back(Info);
// Search backward from BB, creating BBInfos along the way and stopping when
// reaching blocks that define the value. Record those defining blocks on
// the RootList.
SmallVector<BasicBlock*, 10> Preds;
while (!WorkList.empty()) {
Info = WorkList.pop_back_val();
Preds.clear();
FindPredecessorBlocks(Info, &Preds, Allocator);
// Treat an unreachable predecessor as a definition with 'undef'.
if (Info->NumPreds == 0) {
Info->AvailableVal = UndefValue::get(PrototypeValue->getType());
Info->DefBB = Info;
RootList.push_back(Info);
continue;
}
for (unsigned p = 0; p != Info->NumPreds; ++p) {
BasicBlock *Pred = Preds[p];
// Check if BBMap already has a BBInfo for the predecessor block.
BBMapTy::value_type &BBMapBucket = BBMap->FindAndConstruct(Pred);
if (BBMapBucket.second) {
Info->Preds[p] = BBMapBucket.second;
continue;
}
// Create a new BBInfo for the predecessor.
Value *PredVal = AvailableVals.lookup(Pred);
BBInfo *PredInfo = new (*Allocator) BBInfo(Pred, PredVal);
BBMapBucket.second = PredInfo;
Info->Preds[p] = PredInfo;
if (PredInfo->AvailableVal) {
RootList.push_back(PredInfo);
continue;
}
WorkList.push_back(PredInfo);
}
}
// Now that we know what blocks are backwards-reachable from the starting
// block, do a forward depth-first traversal to assign postorder numbers
// to those blocks.
BBInfo *PseudoEntry = new (*Allocator) BBInfo(0, 0);
unsigned BlkNum = 1;
// Initialize the worklist with the roots from the backward traversal.
while (!RootList.empty()) {
Info = RootList.pop_back_val();
Info->IDom = PseudoEntry;
Info->BlkNum = -1;
WorkList.push_back(Info);
}
while (!WorkList.empty()) {
Info = WorkList.back();
if (Info->BlkNum == -2) {
// All the successors have been handled; assign the postorder number.
Info->BlkNum = BlkNum++;
// If not a root, put it on the BlockList.
if (!Info->AvailableVal)
BlockList->push_back(Info);
WorkList.pop_back();
continue;
}
// Leave this entry on the worklist, but set its BlkNum to mark that its
// successors have been put on the worklist. When it returns to the top
// the list, after handling its successors, it will be assigned a number.
Info->BlkNum = -2;
// Add unvisited successors to the work list.
for (succ_iterator SI = succ_begin(Info->BB), E = succ_end(Info->BB);
SI != E; ++SI) {
BBInfo *SuccInfo = (*BBMap)[*SI];
if (!SuccInfo || SuccInfo->BlkNum)
continue;
SuccInfo->BlkNum = -1;
WorkList.push_back(SuccInfo);
}
}
PseudoEntry->BlkNum = BlkNum;
}
/// IntersectDominators - This is the dataflow lattice "meet" operation for
/// finding dominators. Given two basic blocks, it walks up the dominator
/// tree until it finds a common dominator of both. It uses the postorder
/// number of the blocks to determine how to do that.
static SSAUpdater::BBInfo *IntersectDominators(SSAUpdater::BBInfo *Blk1,
SSAUpdater::BBInfo *Blk2) {
while (Blk1 != Blk2) {
while (Blk1->BlkNum < Blk2->BlkNum) {
Blk1 = Blk1->IDom;
if (!Blk1)
return Blk2;
}
while (Blk2->BlkNum < Blk1->BlkNum) {
Blk2 = Blk2->IDom;
if (!Blk2)
return Blk1;
}
}
return Blk1;
}
/// FindDominators - Calculate the dominator tree for the subset of the CFG
/// corresponding to the basic blocks on the BlockList. This uses the
/// algorithm from: "A Simple, Fast Dominance Algorithm" by Cooper, Harvey and
/// Kennedy, published in Software--Practice and Experience, 2001, 4:1-10.
/// Because the CFG subset does not include any edges leading into blocks that
/// define the value, the results are not the usual dominator tree. The CFG
/// subset has a single pseudo-entry node with edges to a set of root nodes
/// for blocks that define the value. The dominators for this subset CFG are
/// not the standard dominators but they are adequate for placing PHIs within
/// the subset CFG.
void SSAUpdater::FindDominators(BlockListTy *BlockList) {
bool Changed;
do {
Changed = false;
// Iterate over the list in reverse order, i.e., forward on CFG edges.
for (BlockListTy::reverse_iterator I = BlockList->rbegin(),
E = BlockList->rend(); I != E; ++I) {
BBInfo *Info = *I;
// Start with the first predecessor.
assert(Info->NumPreds > 0 && "unreachable block");
BBInfo *NewIDom = Info->Preds[0];
// Iterate through the block's other predecessors.
for (unsigned p = 1; p != Info->NumPreds; ++p) {
BBInfo *Pred = Info->Preds[p];
NewIDom = IntersectDominators(NewIDom, Pred);
}
// Check if the IDom value has changed.
if (NewIDom != Info->IDom) {
Info->IDom = NewIDom;
Changed = true;
}
}
} while (Changed);
}
/// IsDefInDomFrontier - Search up the dominator tree from Pred to IDom for
/// any blocks containing definitions of the value. If one is found, then the
/// successor of Pred is in the dominance frontier for the definition, and
/// this function returns true.
static bool IsDefInDomFrontier(const SSAUpdater::BBInfo *Pred,
const SSAUpdater::BBInfo *IDom) {
for (; Pred != IDom; Pred = Pred->IDom) {
if (Pred->DefBB == Pred)
return true;
}
return false;
}
/// FindPHIPlacement - PHIs are needed in the iterated dominance frontiers of
/// the known definitions. Iteratively add PHIs in the dom frontiers until
/// nothing changes. Along the way, keep track of the nearest dominating
/// definitions for non-PHI blocks.
void SSAUpdater::FindPHIPlacement(BlockListTy *BlockList) {
bool Changed;
do {
Changed = false;
// Iterate over the list in reverse order, i.e., forward on CFG edges.
for (BlockListTy::reverse_iterator I = BlockList->rbegin(),
E = BlockList->rend(); I != E; ++I) {
BBInfo *Info = *I;
// If this block already needs a PHI, there is nothing to do here.
if (Info->DefBB == Info)
continue;
// Default to use the same def as the immediate dominator.
BBInfo *NewDefBB = Info->IDom->DefBB;
for (unsigned p = 0; p != Info->NumPreds; ++p) {
if (IsDefInDomFrontier(Info->Preds[p], Info->IDom)) {
// Need a PHI here.
NewDefBB = Info;
break;
}
}
// Check if anything changed.
if (NewDefBB != Info->DefBB) {
Info->DefBB = NewDefBB;
Changed = true;
}
}
} while (Changed);
}
/// FindAvailableVal - If this block requires a PHI, first check if an existing
/// PHI matches the PHI placement and reaching definitions computed earlier,
/// and if not, create a new PHI. Visit all the block's predecessors to
/// calculate the available value for each one and fill in the incoming values
/// for a new PHI.
void SSAUpdater::FindAvailableVals(BlockListTy *BlockList) {
AvailableValsTy &AvailableVals = getAvailableVals(AV);
// Go through the worklist in forward order (i.e., backward through the CFG)
// and check if existing PHIs can be used. If not, create empty PHIs where
// they are needed.
for (BlockListTy::iterator I = BlockList->begin(), E = BlockList->end();
I != E; ++I) {
BBInfo *Info = *I;
// Check if there needs to be a PHI in BB.
if (Info->DefBB != Info)
continue;
// Look for an existing PHI.
FindExistingPHI(Info->BB, BlockList);
if (Info->AvailableVal)
continue;
PHINode *PHI = PHINode::Create(PrototypeValue->getType(),
PrototypeValue->getName(),
&Info->BB->front());
PHI->reserveOperandSpace(Info->NumPreds);
Info->AvailableVal = PHI;
AvailableVals[Info->BB] = PHI;
}
// Now go back through the worklist in reverse order to fill in the arguments
// for any new PHIs added in the forward traversal.
for (BlockListTy::reverse_iterator I = BlockList->rbegin(),
E = BlockList->rend(); I != E; ++I) {
BBInfo *Info = *I;
if (Info->DefBB != Info) {
// Record the available value at join nodes to speed up subsequent
// uses of this SSAUpdater for the same value.
if (Info->NumPreds > 1)
AvailableVals[Info->BB] = Info->DefBB->AvailableVal;
continue;
}
// Check if this block contains a newly added PHI.
PHINode *PHI = dyn_cast<PHINode>(Info->AvailableVal);
if (!PHI || PHI->getNumIncomingValues() == Info->NumPreds)
continue;
// Iterate through the block's predecessors.
for (unsigned p = 0; p != Info->NumPreds; ++p) {
BBInfo *PredInfo = Info->Preds[p];
BasicBlock *Pred = PredInfo->BB;
// Skip to the nearest preceding definition.
if (PredInfo->DefBB != PredInfo)
PredInfo = PredInfo->DefBB;
PHI->addIncoming(PredInfo->AvailableVal, Pred);
}
DEBUG(dbgs() << " Inserted PHI: " << *PHI << "\n");
// If the client wants to know about all new instructions, tell it.
if (InsertedPHIs) InsertedPHIs->push_back(PHI);
}
}
/// FindExistingPHI - Look through the PHI nodes in a block to see if any of
/// them match what is needed.
void SSAUpdater::FindExistingPHI(BasicBlock *BB, BlockListTy *BlockList) {
PHINode *SomePHI;
for (BasicBlock::iterator It = BB->begin();
(SomePHI = dyn_cast<PHINode>(It)); ++It) {
if (CheckIfPHIMatches(SomePHI)) {
RecordMatchingPHI(SomePHI);
break;
}
// Match failed: clear all the PHITag values.
for (BlockListTy::iterator I = BlockList->begin(), E = BlockList->end();
I != E; ++I)
(*I)->PHITag = 0;
}
}
/// CheckIfPHIMatches - Check if a PHI node matches the placement and values
/// in the BBMap.
bool SSAUpdater::CheckIfPHIMatches(PHINode *PHI) {
BBMapTy *BBMap = getBBMap(BM);
SmallVector<PHINode*, 20> WorkList;
WorkList.push_back(PHI);
// Mark that the block containing this PHI has been visited.
(*BBMap)[PHI->getParent()]->PHITag = PHI;
while (!WorkList.empty()) {
PHI = WorkList.pop_back_val();
// Iterate through the PHI's incoming values.
for (unsigned i = 0, e = PHI->getNumIncomingValues(); i != e; ++i) {
Value *IncomingVal = PHI->getIncomingValue(i);
BBInfo *PredInfo = (*BBMap)[PHI->getIncomingBlock(i)];
// Skip to the nearest preceding definition.
if (PredInfo->DefBB != PredInfo)
PredInfo = PredInfo->DefBB;
// Check if it matches the expected value.
if (PredInfo->AvailableVal) {
if (IncomingVal == PredInfo->AvailableVal)
continue;
return false;
}
// Check if the value is a PHI in the correct block.
PHINode *IncomingPHIVal = dyn_cast<PHINode>(IncomingVal);
if (!IncomingPHIVal || IncomingPHIVal->getParent() != PredInfo->BB)
return false;
// If this block has already been visited, check if this PHI matches.
if (PredInfo->PHITag) {
if (IncomingPHIVal == PredInfo->PHITag)
continue;
return false;
}
PredInfo->PHITag = IncomingPHIVal;
WorkList.push_back(IncomingPHIVal);
}
}
return true;
}
/// RecordMatchingPHI - For a PHI node that matches, record it and its input
/// PHIs in both the BBMap and the AvailableVals mapping.
void SSAUpdater::RecordMatchingPHI(PHINode *PHI) {
BBMapTy *BBMap = getBBMap(BM);
AvailableValsTy &AvailableVals = getAvailableVals(AV);
SmallVector<PHINode*, 20> WorkList;
WorkList.push_back(PHI);
// Record this PHI.
BasicBlock *BB = PHI->getParent();
AvailableVals[BB] = PHI;
(*BBMap)[BB]->AvailableVal = PHI;
while (!WorkList.empty()) {
PHI = WorkList.pop_back_val();
// Iterate through the PHI's incoming values.
for (unsigned i = 0, e = PHI->getNumIncomingValues(); i != e; ++i) {
PHINode *IncomingPHIVal = dyn_cast<PHINode>(PHI->getIncomingValue(i));
if (!IncomingPHIVal) continue;
BB = IncomingPHIVal->getParent();
BBInfo *Info = (*BBMap)[BB];
if (!Info || Info->AvailableVal)
continue;
// Record the PHI and add it to the worklist.
AvailableVals[BB] = IncomingPHIVal;
Info->AvailableVal = IncomingPHIVal;
WorkList.push_back(IncomingPHIVal);
}
}
SSAUpdaterImpl<SSAUpdater> Impl(this, &AvailableVals, InsertedPHIs);
return Impl.GetValue(BB);
}