/// CheckAggExprForMemSetUse - If the initializer is large and has a lot of
/// zeros in it, emit a memset and avoid storing the individual zeros.
///
static void CheckAggExprForMemSetUse(AggValueSlot &Slot, const Expr *E,
CodeGenFunction &CGF) {
// If the slot is already known to be zeroed, nothing to do. Don't mess with
// volatile stores.
if (Slot.isZeroed() || Slot.isVolatile() || Slot.getAddr() == 0) return;
// If the type is 16-bytes or smaller, prefer individual stores over memset.
std::pair<uint64_t, unsigned> TypeInfo =
CGF.getContext().getTypeInfo(E->getType());
if (TypeInfo.first/8 <= 16)
return;
// Check to see if over 3/4 of the initializer are known to be zero. If so,
// we prefer to emit memset + individual stores for the rest.
uint64_t NumNonZeroBytes = GetNumNonZeroBytesInInit(E, CGF);
if (NumNonZeroBytes*4 > TypeInfo.first/8)
return;
// Okay, it seems like a good idea to use an initial memset, emit the call.
llvm::Constant *SizeVal = CGF.Builder.getInt64(TypeInfo.first/8);
unsigned Align = TypeInfo.second/8;
llvm::Value *Loc = Slot.getAddr();
const llvm::Type *BP = llvm::Type::getInt8PtrTy(CGF.getLLVMContext());
Loc = CGF.Builder.CreateBitCast(Loc, BP);
CGF.Builder.CreateMemSet(Loc, CGF.Builder.getInt8(0), SizeVal, Align, false);
// Tell the AggExprEmitter that the slot is known zero.
Slot.setZeroed();
}
/// CheckAggExprForMemSetUse - If the initializer is large and has a lot of
/// zeros in it, emit a memset and avoid storing the individual zeros.
///
static void CheckAggExprForMemSetUse(AggValueSlot &Slot, const Expr *E,
CodeGenFunction &CGF) {
// If the slot is already known to be zeroed, nothing to do. Don't mess with
// volatile stores.
if (Slot.isZeroed() || Slot.isVolatile() || Slot.getAddr() == 0) return;
// C++ objects with a user-declared constructor don't need zero'ing.
if (CGF.getContext().getLangOptions().CPlusPlus)
if (const RecordType *RT = CGF.getContext()
.getBaseElementType(E->getType())->getAs<RecordType>()) {
const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl());
if (RD->hasUserDeclaredConstructor())
return;
}
// If the type is 16-bytes or smaller, prefer individual stores over memset.
std::pair<CharUnits, CharUnits> TypeInfo =
CGF.getContext().getTypeInfoInChars(E->getType());
if (TypeInfo.first <= CharUnits::fromQuantity(16))
return;
// Check to see if over 3/4 of the initializer are known to be zero. If so,
// we prefer to emit memset + individual stores for the rest.
CharUnits NumNonZeroBytes = GetNumNonZeroBytesInInit(E, CGF);
if (NumNonZeroBytes*4 > TypeInfo.first)
return;
// Okay, it seems like a good idea to use an initial memset, emit the call.
llvm::Constant *SizeVal = CGF.Builder.getInt64(TypeInfo.first.getQuantity());
CharUnits Align = TypeInfo.second;
llvm::Value *Loc = Slot.getAddr();
llvm::Type *BP = llvm::Type::getInt8PtrTy(CGF.getLLVMContext());
Loc = CGF.Builder.CreateBitCast(Loc, BP);
CGF.Builder.CreateMemSet(Loc, CGF.Builder.getInt8(0), SizeVal,
Align.getQuantity(), false);
// Tell the AggExprEmitter that the slot is known zero.
Slot.setZeroed();
}
