Add `vk::offset` to specify member offsets for push constants (#6797)

* Add struct member offset qualifier for SPIRV

* Implement for GLSL target and add tests

* clean up

* fix formatting

* fix typo

* renamed GLSLStructOffset to VkStructOffset and added emit-spirv-via-glsl test case

1 files changed, 34 insertions, 0 deletions

diff --git a/tests/diagnostics/vk-offset.slang b/tests/diagnostics/vk-offset.slang
new file mode 100644
index 000000000..5dbd821c6
--- /dev/null
+++ b/tests/diagnostics/vk-offset.slang
@@ -0,0 +1,34 @@
+//DIAGNOSTIC_TEST:SIMPLE(filecheck=CHECK): -target spirv -emit-spirv-directly -entry vertexMain -stage vertex
+
+// CHECK: error 31002: attribute 'vk_offset' is not valid here
+// CHECK-NEXT: [vk::offset(16)]] struct S1
+// CHECK: error 31002: attribute 'vk_offset' is not valid here
+// CHECK-NEXT: [vk::offset(8)]] VertexOutput output;
+
+[[vk::offset(16)]] struct S1
+{
+    [[vk::offset(32)]]
+    float2 a;
+
+    float3 b;
+
+    [[vk::offset(16)]]
+    float4 c;
+  }
+
+[[vk::push_constant]]
+S1 pc;
+
+struct VertexOutput
+{
+    float3 position : SV_Position;
+}
+
+[shader("vertex")]
+VertexOutput vertexMain()
+{
+    [[vk::offset(8)]] VertexOutput output;
+    output.position = float3(pc.a.x, pc.b.y, pc.c.z);
+    return output;
+}
+