Fix FragSizeEXT builtin type to require vec2<i32> not vec2<f32>

FragSizeEXT is a two-component vector of integers per the
SPV_EXT_fragment_invocation_density spec. The validation was
incorrectly requiring vec2<f32>.

Author: LegNeato

rust/spirv-tools-core/src/validation/rules/builtins.rs

@@ -539,7 +539,7 @@ fn validate_builtin_type(
         }
 
         // === vec2<f32> builtins ===
-        BuiltIn::PointCoord | BuiltIn::SamplePosition | BuiltIn::FragSizeEXT => {
+        BuiltIn::PointCoord | BuiltIn::SamplePosition => {
             if !is_vec2_f32(pointee, definitions) {
                 return Some(ValidationError::InvalidBuiltInType {
                     builtin,
@@ -548,6 +548,16 @@ fn validate_builtin_type(
             }
         }
 
+        // === vec2<i32/u32> builtins ===
+        BuiltIn::FragSizeEXT => {
+            if !is_vec2_i32(pointee, definitions) {
+                return Some(ValidationError::InvalidBuiltInType {
+                    builtin,
+                    expected: "vec2<i32>",
+                });
+            }
+        }
+
         // === vec3<i32/u32> builtins ===
         BuiltIn::GlobalInvocationId
         | BuiltIn::LocalInvocationId
@@ -841,8 +851,6 @@ fn is_vec4_i32(ty: &Instruction, definitions: &HashMap<ResultId, Instruction>) -
     is_vec_of(ty, definitions, 4, Op::TypeInt, 32)
 }
 
-// Helper functions for mesh shader type validation
-#[allow(dead_code)]
 fn is_vec2_i32(ty: &Instruction, definitions: &HashMap<ResultId, Instruction>) -> bool {
     is_vec_of(ty, definitions, 2, Op::TypeInt, 32)
 }

rust/spirv-tools-core/src/validation/tests/mod.rs

@@ -30486,3 +30486,66 @@ fn clip_distance_input_accepted_in_fragment_with_separate_vertex_entry() {
         .validate(TargetEnv::Vulkan1_1)
         .expect("ClipDistance Input should be accepted in Fragment shader");
 }
+
+#[test]
+fn frag_size_ext_rejects_float_type() {
+    // FragSizeEXT must be vec2<i32>, not vec2<f32>
+    let text = [
+        "OpCapability Shader",
+        "OpCapability FragmentDensityEXT",
+        "OpExtension \"SPV_EXT_fragment_invocation_density\"",
+        "OpMemoryModel Logical GLSL450",
+        "OpEntryPoint Fragment %main \"main\" %fs",
+        "OpExecutionMode %main OriginUpperLeft",
+        "%void = OpTypeVoid",
+        "%float = OpTypeFloat 32",
+        "%v2f = OpTypeVector %float 2",
+        "%ptr_input_v2f = OpTypePointer Input %v2f",
+        "%fs = OpVariable %ptr_input_v2f Input",
+        "OpDecorate %fs BuiltIn FragSizeEXT",
+        "OpDecorate %fs Flat",
+        "%fn = OpTypeFunction %void",
+        "%main = OpFunction %void None %fn",
+        "%entry = OpLabel",
+        "OpReturn",
+        "OpFunctionEnd",
+    ]
+    .join("\n");
+    let error = text
+        .as_str()
+        .validate(TargetEnv::Vulkan1_1)
+        .expect_err("FragSizeEXT with vec2<f32> should be rejected");
+    assert!(
+        matches!(error, ValidationError::InvalidBuiltInType { .. }),
+        "Expected InvalidBuiltInType, got: {error:?}"
+    );
+}
+
+#[test]
+fn frag_size_ext_accepts_integer_vec2_type() {
+    // FragSizeEXT must be vec2<i32/u32>
+    let text = [
+        "OpCapability Shader",
+        "OpCapability FragmentDensityEXT",
+        "OpExtension \"SPV_EXT_fragment_invocation_density\"",
+        "OpMemoryModel Logical GLSL450",
+        "OpEntryPoint Fragment %main \"main\" %fs",
+        "OpExecutionMode %main OriginUpperLeft",
+        "%void = OpTypeVoid",
+        "%uint = OpTypeInt 32 0",
+        "%v2u = OpTypeVector %uint 2",
+        "%ptr_input_v2u = OpTypePointer Input %v2u",
+        "%fs = OpVariable %ptr_input_v2u Input",
+        "OpDecorate %fs BuiltIn FragSizeEXT",
+        "OpDecorate %fs Flat",
+        "%fn = OpTypeFunction %void",
+        "%main = OpFunction %void None %fn",
+        "%entry = OpLabel",
+        "OpReturn",
+        "OpFunctionEnd",
+    ]
+    .join("\n");
+    text.as_str()
+        .validate(TargetEnv::Vulkan1_1)
+        .expect("FragSizeEXT with vec2<u32> should be accepted");
+}