/// ComputeValueVTs - Given an LLVM IR type, compute a sequence of
/// EVTs that represent all the individual underlying
/// non-aggregate types that comprise it.
///
/// If Offsets is non-null, it points to a vector to be filled in
/// with the in-memory offsets of each of the individual values.
///
void llvm::ComputeValueVTs(const TargetLowering &TLI, Type *Ty,
SmallVectorImpl<EVT> &ValueVTs,
SmallVectorImpl<uint64_t> *Offsets,
uint64_t StartingOffset) {
// Given a struct type, recursively traverse the elements.
if (StructType *STy = dyn_cast<StructType>(Ty)) {
const StructLayout *SL = TLI.getDataLayout()->getStructLayout(STy);
for (StructType::element_iterator EB = STy->element_begin(),
EI = EB,
EE = STy->element_end();
EI != EE; ++EI)
ComputeValueVTs(TLI, *EI, ValueVTs, Offsets,
StartingOffset + SL->getElementOffset(EI - EB));
return;
}
// Given an array type, recursively traverse the elements.
if (ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
Type *EltTy = ATy->getElementType();
uint64_t EltSize = TLI.getDataLayout()->getTypeAllocSize(EltTy);
for (unsigned i = 0, e = ATy->getNumElements(); i != e; ++i)
ComputeValueVTs(TLI, EltTy, ValueVTs, Offsets,
StartingOffset + i * EltSize);
return;
}
// Interpret void as zero return values.
if (Ty->isVoidTy())
return;
// Base case: we can get an EVT for this LLVM IR type.
ValueVTs.push_back(TLI.getValueType(Ty));
if (Offsets)
Offsets->push_back(StartingOffset);
}
/// OptimizeNoopCopyExpression - If the specified cast instruction is a noop
/// copy (e.g. it's casting from one pointer type to another, i32->i8 on PPC),
/// sink it into user blocks to reduce the number of virtual
/// registers that must be created and coalesced.
///
/// Return true if any changes are made.
///
static bool OptimizeNoopCopyExpression(CastInst *CI, const TargetLowering &TLI) {
// If this is a noop copy,
EVT SrcVT = TLI.getValueType(CI->getOperand(0)->getType());
EVT DstVT = TLI.getValueType(CI->getType());
// This is an fp<->int conversion?
if (SrcVT.isInteger() != DstVT.isInteger())
return false;
// If this is an extension, it will be a zero or sign extension, which
// isn't a noop.
if (SrcVT.bitsLT(DstVT)) return false;
// If these values will be promoted, find out what they will be promoted
// to. This helps us consider truncates on PPC as noop copies when they
// are.
if (TLI.getTypeAction(CI->getContext(), SrcVT) ==
TargetLowering::TypePromoteInteger)
SrcVT = TLI.getTypeToTransformTo(CI->getContext(), SrcVT);
if (TLI.getTypeAction(CI->getContext(), DstVT) ==
TargetLowering::TypePromoteInteger)
DstVT = TLI.getTypeToTransformTo(CI->getContext(), DstVT);
// If, after promotion, these are the same types, this is a noop copy.
if (SrcVT != DstVT)
return false;
BasicBlock *DefBB = CI->getParent();
/// InsertedCasts - Only insert a cast in each block once.
DenseMap<BasicBlock*, CastInst*> InsertedCasts;
bool MadeChange = false;
for (Value::use_iterator UI = CI->use_begin(), E = CI->use_end();
UI != E; ) {
Use &TheUse = UI.getUse();
Instruction *User = cast<Instruction>(*UI);
// Figure out which BB this cast is used in. For PHI's this is the
// appropriate predecessor block.
BasicBlock *UserBB = User->getParent();
if (PHINode *PN = dyn_cast<PHINode>(User)) {
UserBB = PN->getIncomingBlock(UI);
}
// Preincrement use iterator so we don't invalidate it.
++UI;
// If this user is in the same block as the cast, don't change the cast.
if (UserBB == DefBB) continue;
// If we have already inserted a cast into this block, use it.
CastInst *&InsertedCast = InsertedCasts[UserBB];
if (!InsertedCast) {
BasicBlock::iterator InsertPt = UserBB->getFirstInsertionPt();
InsertedCast =
CastInst::Create(CI->getOpcode(), CI->getOperand(0), CI->getType(), "",
InsertPt);
MadeChange = true;
}
// Replace a use of the cast with a use of the new cast.
TheUse = InsertedCast;
++NumCastUses;
}
// If we removed all uses, nuke the cast.
if (CI->use_empty()) {
CI->eraseFromParent();
MadeChange = true;
}
return MadeChange;
}
