[Vulkan] Avoid explicit layout decoration on non-interface allocations

[kabu1204]

SPIR-V codegen currently emits ArrayStride and Offset decorations for non-interface allocations in GetStructArrayType(). That is correct for descriptor-backed interface blocks, but not for static workgroup allocations.

I hit this while bringing up tilelang vulkan shared memory allocation path: the vulkan validation rejected shaders that used shared memory lowered through this path:

tvm.error.InternalError: Check failed: res == SPV_SUCCESS (-10 vs. 0) :
index=44 error:[VUID-StandaloneSpirv-None-10684] Invalid explicit layout decorations on type for operand '25[%_ptr_Workgroup__struct_24]'
  %A_shared = OpVariable %_ptr_Workgroup__struct_24 Workgroup

FIX: This PR keeps layout decoration for interface blocks, and skips for non-interface allocations such as static shared/workgroup memory. A new compile-only test is added for this.

One possible concern is that there's already a pre-existing test using fetch_to_shared.

[gemini-code-assist]

Summary of Changes

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This pull request refines the SPIR-V code generation process to prevent Vulkan validation errors that occurred when explicit layout decorations were incorrectly applied to non-interface allocations, such as static shared memory. By making these decorations conditional, the system now correctly distinguishes between interface blocks requiring explicit layouts and other memory types, ensuring shader validity.

Highlights

• Conditional Layout Decorations: SPIR-V ArrayStride and Offset decorations are now applied conditionally, only for descriptor-backed interface blocks.
• Fixes Vulkan Validation Error: This change resolves a Vulkan validation error related to invalid explicit layout decorations on non-interface allocations, specifically static workgroup memory.
• New Test Case: A compile-only test test_codegen_static_shared_memory was added to verify the correct handling of static shared/workgroup memory allocations.

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Code Review

This pull request addresses an issue in the SPIR-V codegen where explicit layout decorations (ArrayStride and Offset) were incorrectly applied to non-interface allocations, such as static workgroup memory, causing validation failures. The fix correctly makes these decorations conditional, applying them only for descriptor-backed interface blocks by checking the interface_block flag in IRBuilder::GetStructArrayType. A new compile-only test, test_codegen_static_shared_memory, is added to verify the fix for static shared memory allocations. The changes are correct and address the described issue.