[wgsl-in] Ensure textureSampleLevel's level argument is an integer for depth textures (#6529)

Until now we accepted a float, as is the case for non-depth textures.
This makes us compliant with the spec.

The validator is updated to expect an Sint or Uint when the ImageClass
is ImageClass::Depth. The SPIR-V frontend converts the LOD argument
from float to Sint (assuming that it is representable), likewise The
SPIR-V backend now converts the LOD from either Sint or Uint to
Float. HLSL and MSL backends require no changes as they implicitly do
that conversion. GLSL does not support non-compare LOD samples,
therefore no changes are required.

naga/src/back/spv/image.rs

@@ -924,7 +924,43 @@ impl<'w> BlockContext<'w> {
                     depth_id,
                 );
 
-                let lod_id = self.cached[lod_handle];
+                let mut lod_id = self.cached[lod_handle];
+                // SPIR-V expects the LOD to be a float for all image classes.
+                // lod_id, however, will be an integer for depth images,
+                // therefore we must do a conversion.
+                if matches!(
+                    self.ir_module.types[image_type].inner,
+                    crate::TypeInner::Image {
+                        class: crate::ImageClass::Depth { .. },
+                        ..
+                    }
+                ) {
+                    let lod_f32_id = self.gen_id();
+                    let f32_type_id = self.get_type_id(LookupType::Local(LocalType::Numeric(
+                        NumericType::Scalar(crate::Scalar::F32),
+                    )));
+                    let convert_op = match *self.fun_info[lod_handle]
+                        .ty
+                        .inner_with(&self.ir_module.types)
+                    {
+                        crate::TypeInner::Scalar(crate::Scalar {
+                            kind: crate::ScalarKind::Uint,
+                            width: 4,
+                        }) => spirv::Op::ConvertUToF,
+                        crate::TypeInner::Scalar(crate::Scalar {
+                            kind: crate::ScalarKind::Sint,
+                            width: 4,
+                        }) => spirv::Op::ConvertSToF,
+                        _ => unreachable!(),
+                    };
+                    block.body.push(Instruction::unary(
+                        convert_op,
+                        f32_type_id,
+                        lod_f32_id,
+                        lod_id,
+                    ));
+                    lod_id = lod_f32_id;
+                }
                 mask |= spirv::ImageOperands::LOD;
                 inst.add_operand(mask.bits());
                 inst.add_operand(lod_id);

naga/src/front/spv/image.rs

@@ -30,6 +30,7 @@ impl<'function> super::BlockContext<'function> {
         match self.expressions[handle] {
             crate::Expression::GlobalVariable(handle) => Ok(self.global_arena[handle].ty),
             crate::Expression::FunctionArgument(i) => Ok(self.arguments[i as usize].ty),
+            crate::Expression::Access { base, .. } => Ok(self.get_image_expr_ty(base)?),
             ref other => Err(Error::InvalidImageExpression(other.clone())),
         }
     }
@@ -460,6 +461,7 @@ impl<I: Iterator<Item = u32>> super::Frontend<I> {
         } else {
             None
         };
+        let span = self.span_from_with_op(start);
 
         let mut image_ops = if words_left != 0 {
             words_left -= 1;
@@ -486,9 +488,34 @@ impl<I: Iterator<Item = u32>> super::Frontend<I> {
                     let lod_lexp = self.lookup_expression.lookup(lod_expr)?;
                     let lod_handle =
                         self.get_expr_handle(lod_expr, lod_lexp, ctx, emitter, block, body_idx);
+
+                    let is_depth_image = {
+                        let image_lexp = self.lookup_sampled_image.lookup(sampled_image_id)?;
+                        let image_ty = ctx.get_image_expr_ty(image_lexp.image)?;
+                        matches!(
+                            ctx.type_arena[image_ty].inner,
+                            crate::TypeInner::Image {
+                                class: crate::ImageClass::Depth { .. },
+                                ..
+                            }
+                        )
+                    };
+
                     level = if options.compare {
                         log::debug!("Assuming {:?} is zero", lod_handle);
                         crate::SampleLevel::Zero
+                    } else if is_depth_image {
+                        log::debug!(
+                            "Assuming level {:?} converts losslessly to an integer",
+                            lod_handle
+                        );
+                        let expr = crate::Expression::As {
+                            expr: lod_handle,
+                            kind: crate::ScalarKind::Sint,
+                            convert: Some(4),
+                        };
+                        let s32_lod_handle = ctx.expressions.append(expr, span);
+                        crate::SampleLevel::Exact(s32_lod_handle)
                     } else {
                         crate::SampleLevel::Exact(lod_handle)
                     };

naga/src/valid/expression.rs

@@ -106,7 +106,7 @@ pub enum ExpressionError {
     InvalidGatherComponent(crate::SwizzleComponent),
     #[error("Gather can't be done for image dimension {0:?}")]
     InvalidGatherDimension(crate::ImageDimension),
-    #[error("Sample level (exact) type {0:?} is not a scalar float")]
+    #[error("Sample level (exact) type {0:?} has an invalid type")]
     InvalidSampleLevelExactType(Handle<crate::Expression>),
     #[error("Sample level (bias) type {0:?} is not a scalar float")]
     InvalidSampleLevelBiasType(Handle<crate::Expression>),
@@ -530,11 +530,24 @@ impl super::Validator {
                     crate::SampleLevel::Auto => ShaderStages::FRAGMENT,
                     crate::SampleLevel::Zero => ShaderStages::all(),
                     crate::SampleLevel::Exact(expr) => {
-                        match resolver[expr] {
+                        match class {
-                            Ti::Scalar(Sc {
+                            crate::ImageClass::Depth { .. } => match resolver[expr] {
-                                kind: Sk::Float, ..
+                                Ti::Scalar(Sc {
-                            }) => {}
+                                    kind: Sk::Sint | Sk::Uint,
-                            _ => return Err(ExpressionError::InvalidSampleLevelExactType(expr)),
+                                    ..
+                                }) => {}
+                                _ => {
+                                    return Err(ExpressionError::InvalidSampleLevelExactType(expr))
+                                }
+                            },
+                            _ => match resolver[expr] {
+                                Ti::Scalar(Sc {
+                                    kind: Sk::Float, ..
+                                }) => {}
+                                _ => {
+                                    return Err(ExpressionError::InvalidSampleLevelExactType(expr))
+                                }
+                            },
                         }
                         ShaderStages::all()
                     }

naga/tests/in/image.wgsl

@@ -185,7 +185,9 @@ fn gather() -> @location(0) vec4<f32> {
 @fragment
 fn depth_no_comparison() -> @location(0) vec4<f32> {
     let tc = vec2<f32>(0.5);
+    let level = 1;
     let s2d = textureSample(image_2d_depth, sampler_reg, tc);
     let s2d_gather = textureGather(image_2d_depth, sampler_reg, tc);
-    return s2d + s2d_gather;
+    let s2d_level = textureSampleLevel(image_2d_depth, sampler_reg, tc, level);
+    return s2d + s2d_gather + s2d_level;
 }

naga/tests/out/hlsl/image.hlsl

@@ -369,5 +369,6 @@ float4 depth_no_comparison() : SV_Target0
     float2 tc_3 = (0.5).xx;
     float s2d_1 = image_2d_depth.Sample(sampler_reg, tc_3);
     float4 s2d_gather = image_2d_depth.Gather(sampler_reg, tc_3);
-    return ((s2d_1).xxxx + s2d_gather);
+    float s2d_level = image_2d_depth.SampleLevel(sampler_reg, tc_3, 1);
+    return (((s2d_1).xxxx + s2d_gather) + (s2d_level).xxxx);
 }

naga/tests/out/msl/image.msl

@@ -265,5 +265,6 @@ fragment depth_no_comparisonOutput depth_no_comparison(
     metal::float2 tc_3 = metal::float2(0.5);
     float s2d_1 = image_2d_depth.sample(sampler_reg, tc_3);
     metal::float4 s2d_gather = image_2d_depth.gather(sampler_reg, tc_3);
-    return depth_no_comparisonOutput { metal::float4(s2d_1) + s2d_gather };
+    float s2d_level = image_2d_depth.sample(sampler_reg, tc_3, metal::level(1));
+    return depth_no_comparisonOutput { (metal::float4(s2d_1) + s2d_gather) + metal::float4(s2d_level) };
 }

naga/tests/out/spv/image.spvasm

@@ -1,7 +1,7 @@
 ; SPIR-V
 ; Version: 1.1
 ; Generator: rspirv
-; Bound: 520
+; Bound: 526
 OpCapability Shader
 OpCapability Image1D
 OpCapability Sampled1D
@@ -687,8 +687,14 @@ OpBranch %512
 %515 = OpCompositeExtract  %7  %514 0
 %516 = OpSampledImage  %428  %511 %510
 %517 = OpImageGather  %23  %516 %280 %198
-%518 = OpCompositeConstruct  %23  %515 %515 %515 %515
+%518 = OpSampledImage  %428  %511 %510
-%519 = OpFAdd  %23  %518 %517
+%520 = OpConvertSToF  %7  %29
-OpStore %508 %519
+%519 = OpImageSampleExplicitLod  %23  %518 %280 Lod %520
+%521 = OpCompositeExtract  %7  %519 0
+%522 = OpCompositeConstruct  %23  %515 %515 %515 %515
+%523 = OpFAdd  %23  %522 %517
+%524 = OpCompositeConstruct  %23  %521 %521 %521 %521
+%525 = OpFAdd  %23  %523 %524
+OpStore %508 %525
 OpReturn
 OpFunctionEnd

naga/tests/out/wgsl/image.wgsl

@@ -235,5 +235,6 @@ fn depth_no_comparison() -> @location(0) vec4<f32> {
     const tc_3 = vec2(0.5f);
     let s2d_1 = textureSample(image_2d_depth, sampler_reg, tc_3);
     let s2d_gather = textureGather(image_2d_depth, sampler_reg, tc_3);
-    return (vec4(s2d_1) + s2d_gather);
+    let s2d_level = textureSampleLevel(image_2d_depth, sampler_reg, tc_3, 1i);
+    return ((vec4(s2d_1) + s2d_gather) + vec4(s2d_level));
 }