diff options
Diffstat (limited to 'third_party/rust/naga/src/front/glsl/offset.rs')
| -rw-r--r-- | third_party/rust/naga/src/front/glsl/offset.rs | 173 |
1 files changed, 173 insertions, 0 deletions
diff --git a/third_party/rust/naga/src/front/glsl/offset.rs b/third_party/rust/naga/src/front/glsl/offset.rs new file mode 100644 index 0000000000..d7950489cb --- /dev/null +++ b/third_party/rust/naga/src/front/glsl/offset.rs @@ -0,0 +1,173 @@ +/*! +Module responsible for calculating the offset and span for types. + +There exists two types of layouts std140 and std430 (there's technically +two more layouts, shared and packed. Shared is not supported by spirv. Packed is +implementation dependent and for now it's just implemented as an alias to +std140). + +The OpenGl spec (the layout rules are defined by the OpenGl spec in section +7.6.2.2 as opposed to the GLSL spec) uses the term basic machine units which are +equivalent to bytes. +*/ + +use super::{ + ast::StructLayout, + error::{Error, ErrorKind}, + Span, +}; +use crate::{proc::Alignment, Arena, Constant, Handle, Type, TypeInner, UniqueArena}; + +/// Struct with information needed for defining a struct member. +/// +/// Returned by [`calculate_offset`](calculate_offset) +#[derive(Debug)] +pub struct TypeAlignSpan { + /// The handle to the type, this might be the same handle passed to + /// [`calculate_offset`](calculate_offset) or a new such a new array type + /// with a different stride set. + pub ty: Handle<Type>, + /// The alignment required by the type. + pub align: Alignment, + /// The size of the type. + pub span: u32, +} + +/// Returns the type, alignment and span of a struct member according to a [`StructLayout`](StructLayout). +/// +/// The functions returns a [`TypeAlignSpan`](TypeAlignSpan) which has a `ty` member +/// this should be used as the struct member type because for example arrays may have to +/// change the stride and as such need to have a different type. +pub fn calculate_offset( + mut ty: Handle<Type>, + meta: Span, + layout: StructLayout, + types: &mut UniqueArena<Type>, + constants: &Arena<Constant>, + errors: &mut Vec<Error>, +) -> TypeAlignSpan { + // When using the std430 storage layout, shader storage blocks will be laid out in buffer storage + // identically to uniform and shader storage blocks using the std140 layout, except + // that the base alignment and stride of arrays of scalars and vectors in rule 4 and of + // structures in rule 9 are not rounded up a multiple of the base alignment of a vec4. + + let (align, span) = match types[ty].inner { + // 1. If the member is a scalar consuming N basic machine units, + // the base alignment is N. + TypeInner::Scalar { width, .. } => (Alignment::from_width(width), width as u32), + // 2. If the member is a two- or four-component vector with components + // consuming N basic machine units, the base alignment is 2N or 4N, respectively. + // 3. If the member is a three-component vector with components consuming N + // basic machine units, the base alignment is 4N. + TypeInner::Vector { size, width, .. } => ( + Alignment::from(size) * Alignment::from_width(width), + size as u32 * width as u32, + ), + // 4. If the member is an array of scalars or vectors, the base alignment and array + // stride are set to match the base alignment of a single array element, according + // to rules (1), (2), and (3), and rounded up to the base alignment of a vec4. + // TODO: Matrices array + TypeInner::Array { base, size, .. } => { + let info = calculate_offset(base, meta, layout, types, constants, errors); + + let name = types[ty].name.clone(); + + // See comment at the beginning of the function + let (align, stride) = if StructLayout::Std430 == layout { + (info.align, info.align.round_up(info.span)) + } else { + let align = info.align.max(Alignment::MIN_UNIFORM); + (align, align.round_up(info.span)) + }; + + let span = match size { + crate::ArraySize::Constant(s) => { + constants[s].to_array_length().unwrap_or(1) * stride + } + crate::ArraySize::Dynamic => stride, + }; + + let ty_span = types.get_span(ty); + ty = types.insert( + Type { + name, + inner: TypeInner::Array { + base: info.ty, + size, + stride, + }, + }, + ty_span, + ); + + (align, span) + } + // 5. If the member is a column-major matrix with C columns and R rows, the + // matrix is stored identically to an array of C column vectors with R + // components each, according to rule (4) + // TODO: Row major matrices + TypeInner::Matrix { + columns, + rows, + width, + } => { + let mut align = Alignment::from(rows) * Alignment::from_width(width); + + // See comment at the beginning of the function + if StructLayout::Std430 != layout { + align = align.max(Alignment::MIN_UNIFORM); + } + + // See comment on the error kind + if StructLayout::Std140 == layout && rows == crate::VectorSize::Bi { + errors.push(Error { + kind: ErrorKind::UnsupportedMatrixTypeInStd140, + meta, + }); + } + + (align, align * columns as u32) + } + TypeInner::Struct { ref members, .. } => { + let mut span = 0; + let mut align = Alignment::ONE; + let mut members = members.clone(); + let name = types[ty].name.clone(); + + for member in members.iter_mut() { + let info = calculate_offset(member.ty, meta, layout, types, constants, errors); + + let member_alignment = info.align; + span = member_alignment.round_up(span); + align = member_alignment.max(align); + + member.ty = info.ty; + member.offset = span; + + span += info.span; + } + + span = align.round_up(span); + + let ty_span = types.get_span(ty); + ty = types.insert( + Type { + name, + inner: TypeInner::Struct { members, span }, + }, + ty_span, + ); + + (align, span) + } + _ => { + errors.push(Error { + kind: ErrorKind::SemanticError("Invalid struct member type".into()), + meta, + }); + (Alignment::ONE, 0) + } + }; + + TypeAlignSpan { ty, align, span } +} |