void VectorBlockGenerator::copyStmt(ScopStmt &Stmt) {
assert(Stmt.isBlockStmt() && "TODO: Only block statements can be copied by "
"the vector block generator");
BasicBlock *BB = Stmt.getBasicBlock();
BasicBlock *CopyBB =
SplitBlock(Builder.GetInsertBlock(), Builder.GetInsertPoint(), &DT, &LI);
CopyBB->setName("polly.stmt." + BB->getName());
Builder.SetInsertPoint(CopyBB->begin());
// Create two maps that store the mapping from the original instructions of
// the old basic block to their copies in the new basic block. Those maps
// are basic block local.
//
// As vector code generation is supported there is one map for scalar values
// and one for vector values.
//
// In case we just do scalar code generation, the vectorMap is not used and
// the scalarMap has just one dimension, which contains the mapping.
//
// In case vector code generation is done, an instruction may either appear
// in the vector map once (as it is calculating >vectorwidth< values at a
// time. Or (if the values are calculated using scalar operations), it
// appears once in every dimension of the scalarMap.
VectorValueMapT ScalarBlockMap(getVectorWidth());
ValueMapT VectorBlockMap;
for (Instruction &Inst : *BB)
copyInstruction(Stmt, &Inst, VectorBlockMap, ScalarBlockMap);
}
void BlockGenerator::copyStmt(ScopStmt &Stmt, ValueMapT &GlobalMap,
LoopToScevMapT <S) {
assert(Stmt.isBlockStmt() &&
"Only block statements can be copied by the block generator");
ValueMapT BBMap;
BasicBlock *BB = Stmt.getBasicBlock();
copyBB(Stmt, BB, BBMap, GlobalMap, LTS);
}
void BlockGenerator::generateScalarStores(ScopStmt &Stmt, BasicBlock *BB,
ValueMapT &BBMap,
ValueMapT &GlobalMap) {
const Region &R = Stmt.getParent()->getRegion();
assert(Stmt.isBlockStmt() && BB == Stmt.getBasicBlock() &&
"Region statements need to use the generateScalarStores() "
"function in the RegionGenerator");
// Set to remember a store to the phiops alloca of a PHINode. It is needed as
// we might have multiple write accesses to the same PHI and while one is the
// self write of the PHI (to the ScalarMap alloca) the other is the write to
// the operand alloca (PHIOpMap).
SmallPtrSet<PHINode *, 4> SeenPHIs;
// Iterate over all accesses in the given statement.
for (MemoryAccess *MA : Stmt) {
// Skip non-scalar and read accesses.
if (!MA->isScalar() || MA->isRead())
continue;
Instruction *ScalarBase = cast<Instruction>(MA->getBaseAddr());
Instruction *ScalarInst = MA->getAccessInstruction();
PHINode *ScalarBasePHI = dyn_cast<PHINode>(ScalarBase);
// Get the alloca node for the base instruction and the value we want to
// store. In total there are 4 options:
// (1) The base is no PHI, hence it is a simple scalar def-use chain.
// (2) The base is a PHI,
// (a) and the write is caused by an operand in the block.
// (b) and it is the PHI self write (same as case (1)).
// (c) (2a) and (2b) are not distinguishable.
// For case (1) and (2b) we get the alloca from the scalar map and the value
// we want to store is initialized with the instruction attached to the
// memory access. For case (2a) we get the alloca from the PHI operand map
// and the value we want to store is initialized with the incoming value for
// this block. The tricky case (2c) is when both (2a) and (2b) match. This
// happens if the PHI operand is in the same block as the PHI. To handle
// that we choose the alloca of (2a) first and (2b) for the next write
// access to that PHI (there must be 2).
Value *ScalarValue = nullptr;
AllocaInst *ScalarAddr = nullptr;
if (!ScalarBasePHI) {
// Case (1)
ScalarAddr = getOrCreateAlloca(ScalarBase, ScalarMap, ".s2a");
ScalarValue = ScalarInst;
} else {
int PHIIdx = ScalarBasePHI->getBasicBlockIndex(BB);
if (ScalarBasePHI != ScalarInst) {
// Case (2a)
assert(PHIIdx >= 0 && "Bad scalar write to PHI operand");
SeenPHIs.insert(ScalarBasePHI);
ScalarAddr = getOrCreateAlloca(ScalarBase, PHIOpMap, ".phiops");
ScalarValue = ScalarBasePHI->getIncomingValue(PHIIdx);
} else if (PHIIdx < 0) {
// Case (2b)
ScalarAddr = getOrCreateAlloca(ScalarBase, ScalarMap, ".s2a");
ScalarValue = ScalarInst;
} else {
// Case (2c)
if (SeenPHIs.insert(ScalarBasePHI).second) {
// First access ==> same as (2a)
ScalarAddr = getOrCreateAlloca(ScalarBase, PHIOpMap, ".phiops");
ScalarValue = ScalarBasePHI->getIncomingValue(PHIIdx);
} else {
// Second access ==> same as (2b)
ScalarAddr = getOrCreateAlloca(ScalarBase, ScalarMap, ".s2a");
ScalarValue = ScalarInst;
}
}
}
ScalarValue =
getNewScalarValue(ScalarValue, R, ScalarMap, BBMap, GlobalMap);
Builder.CreateStore(ScalarValue, ScalarAddr);
}
}
