Introduce CDataLayout & -fvk-use-c-layout (#8136)

Closes #8112. ~~The issue asks for a "C layout", but in this PR I use
the term "CPU layout" because this naming was pre-existing in the
codebase as `kCPULayoutRulesImpl_`. The primary purpose of this layout
is to match CPU-side struct definitions with the shader side. I'm open
to better naming suggestions, though.~~

Edit: switched back to using `CDataLayout` & `-fvk-use-c-layout`, as the
CPU target depends on the object layout rules of existing CPU layout
rules, but they're incompatible with actual shaders. So a new
`kCLayoutRulesImpl_` was needed anyway.

---------

Co-authored-by: Ellie Hermaszewska <ellieh@nvidia.com>

1 files changed, 57 insertions, 0 deletions

diff --git a/tests/spirv/c-layout-buffer-2.slang b/tests/spirv/c-layout-buffer-2.slang
new file mode 100644
index 000000000..0d388d095
--- /dev/null
+++ b/tests/spirv/c-layout-buffer-2.slang
@@ -0,0 +1,57 @@
+//TEST:SIMPLE(filecheck=SPIRV): -stage closesthit -entry chit -target spirv -fvk-use-c-layout
+struct RayPayload
+{
+    float3 color;
+};
+
+struct A {
+    int64_t a1;
+    int32_t a2;
+};
+
+struct B {
+    A a;
+    uint32_t b;
+};
+
+struct Push {
+    B *p;
+};
+
+[[vk::push_constant]] Push push;
+
+struct C {
+    int i;
+    A a;
+};
+
+struct D {
+    C c;
+    int j;
+};
+
+[[vk::shader_record]]
+cbuffer ShaderRecord
+{
+    D d;
+}
+
+[[shader("closesthit")]]
+void chit(inout RayPayload payload : SV_RayPayload, in float2 barys_yz : SV_IntersectionAttributes) {
+    let barys = float3(1.0 - barys_yz.x - barys_yz.y, barys_yz);
+    payload.color = barys;
+
+    push.p->b = d.j + d.c.i;
+}
+
+// SPIRV: OpMemberDecorate %A_c 0 Offset 0
+// SPIRV: OpMemberDecorate %A_c 1 Offset 8
+// SPIRV: OpMemberDecorate %C_c 0 Offset 0
+// SPIRV: OpMemberDecorate %C_c 1 Offset 8
+// SPIRV: OpMemberDecorate %D_c 0 Offset 0
+// SPIRV: OpMemberDecorate %D_c 1 Offset 24
+// SPIRV: OpMemberDecorate %B_c 0 Offset 0
+// SPIRV: OpMemberDecorate %B_c 1 Offset 16
+
+// SPIRV: %_ptr_PushConstant_Push_c = OpTypePointer PushConstant %Push_c
+// SPIRV: %_ptr_ShaderRecordBufferKHR_SLANG_ParameterGroup_ShaderRecord_c = OpTypePointer ShaderRecordBufferKHR %SLANG_ParameterGroup_ShaderRecord_c