/// <summary cref="IValueVisitor.Visit(AlignViewTo)"/> public void Visit(AlignViewTo value) => throw new InvalidCodeGenerationException();
/// <summary>
/// Lowers an align-view-to operation.
/// </summary>
private static void Lower(
RewriterContext context,
TypeLowering <ViewType> typeLowering,
AlignViewTo value)
{
var builder = context.Builder;
var location = value.Location;
// Extract basic view information from the converted structure
var pointer = builder.CreateGetField(
location,
value.View,
new FieldSpan(0));
var length = builder.CreateGetField(
location,
value.View,
new FieldSpan(1));
// Create IR code that represents the required operations to create aligned
// views (see ArrayView.AlignToInternal for more information).
var viewType = typeLowering[value].As <ViewType>(value);
// long elementsToSkip = Min(
// AlignmentOffset(ptr, alignmentInBytes) / elementSize,
// Length);
var elementsToSkip = builder.CreateArithmetic(
location,
builder.CreateAlignmentOffset(
location,
builder.CreatePointerAsIntCast(
location,
pointer,
BasicValueType.Int64),
value.AlignmentInBytes),
builder.CreateSizeOf(location, viewType.ElementType),
BinaryArithmeticKind.Div);
elementsToSkip = builder.CreateArithmetic(
location,
elementsToSkip,
length,
BinaryArithmeticKind.Min);
// Build the final result structure instance
var resultBuilder = builder.CreateDynamicStructure(location);
// Create the prefix view that starts at the original pointer offset and
// includes elementsToSkip many elements.
{
resultBuilder.Add(pointer);
resultBuilder.Add(elementsToSkip);
}
// Create the main view that starts at the original pointer offset +
// elementsToSkip and has a length of remainingLength
{
var mainPointer = builder.CreateLoadElementAddress(
location,
pointer,
elementsToSkip);
resultBuilder.Add(mainPointer);
var remainingLength = builder.CreateArithmetic(
location,
length,
elementsToSkip,
BinaryArithmeticKind.Sub);
resultBuilder.Add(remainingLength);
}
var result = resultBuilder.Seal();
context.ReplaceAndRemove(value, result);
}
