Added read_subpass for SubpassData images, and necessary attrs for it.

crates/rustc_codegen_spirv/src/attr.rs

@@ -96,6 +96,7 @@ pub enum SpirvAttribute {
     Binding(u32),
     Flat,
     Invariant,
+    InputAttachmentIndex(u32),
 
     // `fn`/closure attributes:
     UnrollLoops,
@@ -130,6 +131,7 @@ pub struct AggregatedSpirvAttributes {
     pub binding: Option<Spanned<u32>>,
     pub flat: Option<Spanned<()>>,
     pub invariant: Option<Spanned<()>>,
+    pub input_attachment_index: Option<Spanned<u32>>,
 
     // `fn`/closure attributes:
     pub unroll_loops: Option<Spanned<()>>,
@@ -215,6 +217,12 @@ impl AggregatedSpirvAttributes {
             Binding(value) => try_insert(&mut self.binding, value, span, "#[spirv(binding)]"),
             Flat => try_insert(&mut self.flat, (), span, "#[spirv(flat)]"),
             Invariant => try_insert(&mut self.invariant, (), span, "#[spirv(invariant)]"),
+            InputAttachmentIndex(value) => try_insert(
+                &mut self.input_attachment_index,
+                value,
+                span,
+                "#[spirv(attachment_index)]",
+            ),
             UnrollLoops => try_insert(&mut self.unroll_loops, (), span, "#[spirv(unroll_loops)]"),
             InternalBufferLoad => try_insert(
                 &mut self.internal_buffer_load,
@@ -308,7 +316,8 @@ impl CheckSpirvAttrVisitor<'_> {
                 | SpirvAttribute::DescriptorSet(_)
                 | SpirvAttribute::Binding(_)
                 | SpirvAttribute::Flat
-                | SpirvAttribute::Invariant => match target {
+                | SpirvAttribute::Invariant
+                | SpirvAttribute::InputAttachmentIndex(_) => match target {
                     Target::Param => {
                         let parent_hir_id = self.tcx.hir().get_parent_node(hir_id);
                         let parent_is_entry_point =

crates/rustc_codegen_spirv/src/codegen_cx/entry.rs

@@ -6,7 +6,9 @@ use crate::builder_spirv::{SpirvValue, SpirvValueExt};
 use crate::codegen_cx::BindlessDescriptorSets;
 use crate::spirv_type::SpirvType;
 use rspirv::dr::Operand;
-use rspirv::spirv::{Capability, Decoration, ExecutionModel, FunctionControl, StorageClass, Word};
+use rspirv::spirv::{
+    Capability, Decoration, Dim, ExecutionModel, FunctionControl, StorageClass, Word,
+};
 use rustc_codegen_ssa::traits::{BaseTypeMethods, BuilderMethods};
 use rustc_data_structures::fx::FxHashMap;
 use rustc_hir as hir;
@@ -663,6 +665,46 @@ impl<'tcx> CodegenCx<'tcx> {
             }
         }
 
+        let is_subpass_input = match self.lookup_type(value_spirv_type) {
+            SpirvType::Image {
+                dim: Dim::DimSubpassData,
+                ..
+            } => true,
+            SpirvType::RuntimeArray { element: elt, .. }
+            | SpirvType::Array { element: elt, .. } => matches!(
+                self.lookup_type(elt),
+                SpirvType::Image {
+                    dim: Dim::DimSubpassData,
+                    ..
+                }
+            ),
+            _ => false,
+        };
+        if let Some(attachment_index) = attrs.input_attachment_index {
+            if is_subpass_input && self.builder.has_capability(Capability::InputAttachment) {
+                self.emit_global().decorate(
+                    var,
+                    Decoration::InputAttachmentIndex,
+                    std::iter::once(Operand::LiteralInt32(attachment_index.value)),
+                )
+            } else if is_subpass_input {
+                self.tcx
+                    .sess
+                    .span_err(hir_param.ty_span, "Missing capability InputAttachment")
+            } else {
+                self.tcx.sess.span_err(
+                    attachment_index.span,
+                    "#[spirv(input_attachment_index)] is only valid on Image types with dim = SubpassData"
+                );
+            }
+            decoration_supersedes_location = true;
+        } else if is_subpass_input {
+            self.tcx.sess.span_err(
+                hir_param.ty_span,
+                "Image types with dim = SubpassData require #[spirv(input_attachment_index)] decoration",
+            )
+        }
+
         // Assign locations from left to right, incrementing each storage class
         // individually.
         // TODO: Is this right for UniformConstant? Do they share locations with

crates/rustc_codegen_spirv/src/symbols.rs

@@ -23,6 +23,7 @@ pub struct Symbols {
     pub entry_point_name: Symbol,
     descriptor_set: Symbol,
     binding: Symbol,
+    input_attachment_index: Symbol,
     image_type: Symbol,
     dim: Symbol,
     depth: Symbol,
@@ -380,6 +381,7 @@ impl Symbols {
             num_traits: Symbol::intern("num_traits"),
             descriptor_set: Symbol::intern("descriptor_set"),
             binding: Symbol::intern("binding"),
+            input_attachment_index: Symbol::intern("input_attachment_index"),
             image_type: Symbol::intern("image_type"),
             dim: Symbol::intern("dim"),
             depth: Symbol::intern("depth"),
@@ -452,6 +454,8 @@ pub(crate) fn parse_attrs_for_checking<'a>(
                     SpirvAttribute::DescriptorSet(parse_attr_int_value(arg)?)
                 } else if arg.has_name(sym.binding) {
                     SpirvAttribute::Binding(parse_attr_int_value(arg)?)
+                } else if arg.has_name(sym.input_attachment_index) {
+                    SpirvAttribute::InputAttachmentIndex(parse_attr_int_value(arg)?)
                 } else {
                     let name = match arg.ident() {
                         Some(i) => i,

crates/spirv-std/src/image.rs

@@ -5,7 +5,7 @@
 #[rustfmt::skip]
 mod params;
 
-pub use self::params::{ImageCoordinate, SampleType};
+pub use self::params::{ImageCoordinate, ImageCoordinateSubpassData, SampleType};
 pub use crate::macros::Image;
 pub use spirv_types::image_params::{
     AccessQualifier, Arrayed, Dimensionality, ImageDepth, ImageFormat, Multisampled, Sampled,
@@ -659,6 +659,55 @@ impl<
     }
 }
 
+impl<
+        SampledType: SampleType<FORMAT>,
+        const DEPTH: ImageDepth,
+        const ARRAYED: Arrayed,
+        const MULTISAMPLED: Multisampled,
+        const FORMAT: ImageFormat,
+        const ACCESS_QUALIFIER: Option<AccessQualifier>,
+    >
+    Image<
+        SampledType,
+        { Dimensionality::SubpassData },
+        DEPTH,
+        ARRAYED,
+        MULTISAMPLED,
+        { Sampled::No },
+        FORMAT,
+        ACCESS_QUALIFIER,
+    >
+{
+    /// Read a texel from subpass input attachment.
+    /// Note: Vulkan only allows the read if the first two components of the coordinate are zero.
+    #[crate::macros::gpu_only]
+    #[doc(alias = "OpImageRead")]
+    pub fn read_subpass<I, V, const N: usize>(
+        &self,
+        coordinate: impl ImageCoordinateSubpassData<I, ARRAYED>,
+    ) -> V
+    where
+        I: Integer,
+        V: Vector<SampledType, N>,
+    {
+        let mut result = V::default();
+
+        unsafe {
+            asm! {
+            "%image = OpLoad _ {this}",
+            "%coordinate = OpLoad _ {coordinate}",
+            "%result = OpImageRead typeof*{result} %image %coordinate",
+            "OpStore {result} %result",
+            this = in(reg) self,
+            coordinate = in(reg) &coordinate,
+            result = in(reg) &mut result,
+            }
+        }
+
+        result
+    }
+}
+
 impl<
         SampledType: SampleType<FORMAT>,
         const DIM: Dimensionality,

crates/spirv-std/src/image/params.rs

@@ -1,5 +1,5 @@
 use super::{Arrayed, Dimensionality, ImageFormat};
-use crate::{scalar::Scalar, vector::Vector};
+use crate::{scalar::Scalar, vector::Vector, integer::Integer};
 
 /// Marker trait for arguments that accept single scalar values or vectors
 /// of scalars.
@@ -72,3 +72,8 @@ impl<V: Vector<S, 3>, S: Scalar> ImageCoordinate<S, { Dimensionality::TwoD }, {
 impl<V: Vector<S, 3>, S: Scalar> ImageCoordinate<S, { Dimensionality::Rect }, { Arrayed::True }> for V {}
 impl<V: Vector<S, 4>, S: Scalar> ImageCoordinate<S, { Dimensionality::Cube }, { Arrayed::True }> for V {}
 impl<V: Vector<S, 4>, S: Scalar> ImageCoordinate<S, { Dimensionality::ThreeD }, { Arrayed::True }> for V {}
+
+/// Marker trait for arguments that are valid for a [`crate::image::Dimensionality::SubpassData`] image query.
+pub trait ImageCoordinateSubpassData<T, const ARRAYED: Arrayed> {}
+impl<V: Vector<I, 2>, I: Integer> ImageCoordinateSubpassData<I, { Arrayed::False }> for V {}
+impl<V: Vector<I, 3>, I: Integer> ImageCoordinateSubpassData<I, { Arrayed::True }> for V {}

tests/ui/image/query/query_levels_err.stderr

@@ -1,12 +1,12 @@
 error: OpImageQueryLevels's image has a dimension of DimRect
-   --> $SPIRV_STD_SRC/image.rs:684:13
+   --> $SPIRV_STD_SRC/image.rs:733:13
     |
-684 | /             asm! {
-685 | |                 "%image = OpLoad _ {this}",
-686 | |                 "{result} = OpImageQueryLevels typeof{result} %image",
-687 | |                 this = in(reg) self,
-688 | |                 result = out(reg) result,
-689 | |             }
+733 | /             asm! {
+734 | |                 "%image = OpLoad _ {this}",
+735 | |                 "{result} = OpImageQueryLevels typeof{result} %image",
+736 | |                 this = in(reg) self,
+737 | |                 result = out(reg) result,
+738 | |             }
     | |_____________^
     |
     = note: Allowed dimensions are 1D, 2D, 3D, and Cube

tests/ui/image/query/query_lod_err.stderr

@@ -1,13 +1,13 @@
 error: OpImageQueryLod's image has a dimension of DimRect
-   --> $SPIRV_STD_SRC/image.rs:717:13
+   --> $SPIRV_STD_SRC/image.rs:766:13
     |
-717 | /             asm! {
-718 | |                 "%typeSampledImage = OpTypeSampledImage typeof*{this}",
-719 | |                 "%image = OpLoad _ {this}",
-720 | |                 "%sampler = OpLoad _ {sampler}",
+766 | /             asm! {
+767 | |                 "%typeSampledImage = OpTypeSampledImage typeof*{this}",
+768 | |                 "%image = OpLoad _ {this}",
+769 | |                 "%sampler = OpLoad _ {sampler}",
 ...   |
-728 | |                 coord = in(reg) &coord
-729 | |             }
+777 | |                 coord = in(reg) &coord
+778 | |             }
     | |_____________^
     |
     = note: Allowed dimensions are 1D, 2D, 3D, and Cube

tests/ui/image/query/query_size_err.stderr

@@ -1,13 +1,13 @@
 error: OpImageQuerySize is invalid for this image type
-   --> $SPIRV_STD_SRC/image.rs:746:13
+   --> $SPIRV_STD_SRC/image.rs:795:13
     |
-746 | /             asm! {
-747 | |                 "%image = OpLoad _ {this}",
-748 | |                 "%result = OpImageQuerySize typeof*{result} %image",
-749 | |                 "OpStore {result} %result",
-750 | |                 this = in(reg) self,
-751 | |                 result = in(reg) &mut result,
-752 | |             }
+795 | /             asm! {
+796 | |                 "%image = OpLoad _ {this}",
+797 | |                 "%result = OpImageQuerySize typeof*{result} %image",
+798 | |                 "OpStore {result} %result",
+799 | |                 this = in(reg) self,
+800 | |                 result = in(reg) &mut result,
+801 | |             }
     | |_____________^
     |
     = note: allowed dimensions are 1D, 2D, 3D, Buffer, Rect, or Cube. if dimension is 1D, 2D, 3D, or Cube, it must have either multisampled be true, *or* sampled of Unknown or No

tests/ui/image/query/query_size_lod_err.stderr

@@ -1,13 +1,13 @@
 error: OpImageQuerySizeLod is invalid for this image type
-   --> $SPIRV_STD_SRC/image.rs:792:13
+   --> $SPIRV_STD_SRC/image.rs:841:13
     |
-792 | /             asm! {
-793 | |                 "%image = OpLoad _ {this}",
-794 | |                 "%result = OpImageQuerySizeLod typeof*{result} %image {lod}",
-795 | |                 "OpStore {result} %result",
+841 | /             asm! {
+842 | |                 "%image = OpLoad _ {this}",
+843 | |                 "%result = OpImageQuerySizeLod typeof*{result} %image {lod}",
+844 | |                 "OpStore {result} %result",
 ...   |
-798 | |                 result = in(reg) &mut result,
-799 | |             }
+847 | |                 result = in(reg) &mut result,
+848 | |             }
     | |_____________^
     |
     = note: The image's dimension must be 1D, 2D, 3D, or Cube. Multisampled must be false.

tests/ui/image/read_subpass.rs

@@ -0,0 +1,13 @@
+// build-pass
+// compile-flags: -C target-feature=+InputAttachment
+
+use spirv_std::{arch, Image};
+
+#[spirv(fragment)]
+pub fn main(
+    #[spirv(descriptor_set = 0, binding = 0, input_attachment_index = 0)] image: &Image!(subpass, type=f32, sampled=false),
+    output: &mut glam::Vec4,
+) {
+    let coords = image.read_subpass(glam::IVec2::new(0, 0));
+    *output = coords;
+}