[spv-out] option to clamp frag_depth

src/back/spv/block.rs

@@ -20,6 +20,87 @@ fn get_dimension(type_inner: &crate::TypeInner) -> Dimension {
 }
 
 impl Writer {
+ // Flip Y coordinate to adjust for coordinate space difference
+ // between SPIR-V and our IR.
+ // The `position_id` argument is a pointer to a `vecN<f32>`,
+ // whose `y` component we will negate.
+ fn write_epilogue_position_y_flip(
+ &mut self,
+ position_id: Word,
+ body: &mut Vec<Instruction>,
+ ) -> Result<(), Error> {
+ let float_ptr_type_id = self.get_type_id(LookupType::Local(LocalType::Value {
+ vector_size: None,
+ kind: crate::ScalarKind::Float,
+ width: 4,
+ pointer_class: Some(spirv::StorageClass::Output),
+ }));
+ let index_y_id = self.get_index_constant(1);
+ let access_id = self.id_gen.next();
+ body.push(Instruction::access_chain(
+ float_ptr_type_id,
+ access_id,
+ position_id,
+ &[index_y_id],
+ ));
+
+ let float_type_id = self.get_type_id(LookupType::Local(LocalType::Value {
+ vector_size: None,
+ kind: crate::ScalarKind::Float,
+ width: 4,
+ pointer_class: None,
+ }));
+ let load_id = self.id_gen.next();
+ body.push(Instruction::load(float_type_id, load_id, access_id, None));
+
+ let neg_id = self.id_gen.next();
+ body.push(Instruction::unary(
+ spirv::Op::FNegate,
+ float_type_id,
+ neg_id,
+ load_id,
+ ));
+
+ body.push(Instruction::store(access_id, neg_id, None));
+ Ok(())
+ }
+
+ // Clamp fragment depth between 0 and 1.
+ fn write_epilogue_frag_depth_clamp(
+ &mut self,
+ frag_depth_id: Word,
+ body: &mut Vec<Instruction>,
+ ) -> Result<(), Error> {
+ let float_type_id = self.get_type_id(LookupType::Local(LocalType::Value {
+ vector_size: None,
+ kind: crate::ScalarKind::Float,
+ width: 4,
+ pointer_class: None,
+ }));
+ let value0_id = self.get_constant_scalar(crate::ScalarValue::Float(0.0), 4);
+ let value1_id = self.get_constant_scalar(crate::ScalarValue::Float(1.0), 4);
+
+ let original_id = self.id_gen.next();
+ body.push(Instruction::load(
+ float_type_id,
+ original_id,
+ frag_depth_id,
+ None,
+ ));
+
+ let clamp_id = self.id_gen.next();
+ body.push(Instruction::ext_inst(
+ self.gl450_ext_inst_id,
+ spirv::GLOp::FClamp,
+ float_type_id,
+ clamp_id,
+ &[original_id, value0_id, value1_id],
+ ));
+
+ body.push(Instruction::store(frag_depth_id, clamp_id, None));
+ Ok(())
+ }
+
  fn write_entry_point_return(
  &mut self,
  value_id: Word,
@@ -44,43 +125,18 @@ impl Writer {
 
  body.push(Instruction::store(res_member.id, member_value_id, None));
 
- // Flip Y coordinate to adjust for coordinate space difference
- // between SPIR-V and our IR.
- if self.flags.contains(WriterFlags::ADJUST_COORDINATE_SPACE)
- && res_member.built_in == Some(crate::BuiltIn::Position)
- {
- let access_id = self.id_gen.next();
- let float_ptr_type_id = self.get_type_id(LookupType::Local(LocalType::Value {
- vector_size: None,
- kind: crate::ScalarKind::Float,
- width: 4,
- pointer_class: Some(spirv::StorageClass::Output),
- }));
- let index_y_id = self.get_index_constant(1);
- body.push(Instruction::access_chain(
- float_ptr_type_id,
- access_id,
- res_member.id,
- &[index_y_id],
- ));
-
- let load_id = self.id_gen.next();
- let float_type_id = self.get_type_id(LookupType::Local(LocalType::Value {
- vector_size: None,
- kind: crate::ScalarKind::Float,
- width: 4,
- pointer_class: None,
- }));
- body.push(Instruction::load(float_type_id, load_id, access_id, None));
-
- let neg_id = self.id_gen.next();
- body.push(Instruction::unary(
- spirv::Op::FNegate,
- float_type_id,
- neg_id,
- load_id,
- ));
- body.push(Instruction::store(access_id, neg_id, None));
+ match res_member.built_in {
+ Some(crate::BuiltIn::Position)
+ if self.flags.contains(WriterFlags::ADJUST_COORDINATE_SPACE) =>
+ {
+ self.write_epilogue_position_y_flip(res_member.id, body)?;
+ }
+ Some(crate::BuiltIn::FragDepth)
+ if self.flags.contains(WriterFlags::CLAMP_FRAG_DEPTH) =>
+ {
+ self.write_epilogue_frag_depth_clamp(res_member.id, body)?;
+ }
+ _ => {}
  }
  }
  Ok(())

src/back/spv/mod.rs

@@ -568,6 +568,8 @@ bitflags::bitflags! {
  /// Emit `PointSize` output builtin to vertex shaders, which is
  /// required for drawing with `PointList` topology.
  const FORCE_POINT_SIZE = 0x8;
+ /// Clamp `BuiltIn::FragDepth` output between 0 and 1.
+ const CLAMP_FRAG_DEPTH = 0x10;
  }
 }
 
@@ -592,7 +594,9 @@ pub struct Options {
 
 impl Default for Options {
  fn default() -> Self {
- let mut flags = WriterFlags::ADJUST_COORDINATE_SPACE | WriterFlags::LABEL_VARYINGS;
+ let mut flags = WriterFlags::ADJUST_COORDINATE_SPACE
+ | WriterFlags::LABEL_VARYINGS
+ | WriterFlags::CLAMP_FRAG_DEPTH;
  if cfg!(debug_assertions) {
  flags |= WriterFlags::DEBUG;
  }

tests/in/interface.param.ron

@@ -4,6 +4,7 @@
  capabilities: [ Shader, SampleRateShading ],
  adjust_coordinate_space: false,
  force_point_size: true,
+ clamp_frag_depth: true,
  separate_entry_points: true,
  ),
  hlsl_custom: true,

tests/out/spv/interface.fragment.spvasm

@@ -1,7 +1,7 @@
 ; SPIR-V
 ; Version: 1.0
 ; Generator: rspirv
-; Bound: 49
+; Bound: 51
 OpCapability Shader
 OpCapability SampleRateShading
 %1 = OpExtInstImport "GLSL.std.450"
@@ -70,9 +70,12 @@ OpBranch %40
 %45 = OpCompositeConstruct %13 %44 %42 %43
 %46 = OpCompositeExtract %4 %45 0
 OpStore %33 %46
-%47 = OpCompositeExtract %6 %45 1
-OpStore %35 %47
-%48 = OpCompositeExtract %4 %45 2
-OpStore %37 %48
+%47 = OpLoad %4 %33
+%48 = OpExtInst %4 %1 FClamp %47 %7 %3
+OpStore %33 %48
+%49 = OpCompositeExtract %6 %45 1
+OpStore %35 %49
+%50 = OpCompositeExtract %4 %45 2
+OpStore %37 %50
 OpReturn
 OpFunctionEnd

tests/out/spv/quad.spvasm

@@ -61,9 +61,9 @@ OpDecorate %60 Location 0
 %26 = OpTypePointer Output %9
 %25 = OpVariable %26 Output
 %28 = OpTypeFunction %2
-%36 = OpTypePointer Output %4
-%38 = OpTypeInt 32 0
-%37 = OpConstant %38 1
+%35 = OpTypePointer Output %4
+%37 = OpTypeInt 32 0
+%36 = OpConstant %37 1
 %42 = OpVariable %19 Input
 %44 = OpVariable %26 Output
 %49 = OpTypeSampledImage %11
@@ -82,10 +82,10 @@ OpBranch %29
 OpStore %23 %33
 %34 = OpCompositeExtract %9 %32 1
 OpStore %25 %34
-%35 = OpAccessChain %36 %25 %37
-%39 = OpLoad %4 %35
+%38 = OpAccessChain %35 %25 %36
+%39 = OpLoad %4 %38
 %40 = OpFNegate %4 %39
-OpStore %35 %40
+OpStore %38 %40
 OpReturn
 OpFunctionEnd
 %45 = OpFunction %2 None %28

tests/snapshots.rs

@@ -62,6 +62,8 @@ struct SpirvOutParameters {
  #[serde(default)]
  force_point_size: bool,
  #[serde(default)]
+ clamp_frag_depth: bool,
+ #[serde(default)]
  separate_entry_points: bool,
 }
 
@@ -201,6 +203,10 @@ fn write_output_spv(
  spv::WriterFlags::FORCE_POINT_SIZE,
  params.spv.force_point_size,
  );
+ flags.set(
+ spv::WriterFlags::CLAMP_FRAG_DEPTH,
+ params.spv.clamp_frag_depth,
+ );
  let options = spv::Options {
  lang_version: (params.spv.version.0, params.spv.version.1),
  flags,