[sycl-post-link] Fix a crash during spec-constant properties generation

[ghost]

The sycl-post-link tool crashed during processing an IR where a
specialization constant with a padding is present, for example a
specialization constant of such type:

struct alignas(32) coeff_str_aligned_t {
  std::array<float, 3> coeffs;
  size_t number;
};

In the IR, the constant looks like the following:

@_ZL8coeff_id = internal addrspace(1) constant %"class.cl::sycl::specialization_id" { %struct.coeff_str_aligned_t { %"class.std::array" zeroinitializer, i64 0, [8 x i8] undef } }, align 32

That '[8 x i8] undef' led to the crash.

This patch fixes the issue and adds the following optimization: if the
default value of a specialization constant or a part of such default value
is undefined, the value (or its part) is passed into an invocation of the
'__spirv_SpecConstantComposite' function as is.

Co-authored-by: Steffen Larsen steffen.larsen@intel.com
Signed-off-by: Pavel Samolysov pavel.samolysov@intel.com

[steffenlarsen]

Would it make sense to add a SYCL test (probably in llvm-test-suite) to ensure that the default values and offsets given to the runtime are correct when encountering this kind of padding?

[ghost]

Good idea, @steffenlarsen I've extended the vector convolution demo test in llvm-test-suite to handle an aligned structure: intel/llvm-test-suite#830

[ghost]

/verify with intel/llvm-test-suite#830

[ghost]

/verify with intel/llvm-test-suite#830

[ghost]

Some problems with the test infrastructure.

[ghost]

/verify with intel/llvm-test-suite#830

[ghost]

I tried the solution locally with this test: https://github.com/intel/llvm-test-suite/pull/830/files#diff-ec64dcd370d47e70aa3c7dcb41f18fb8780a11422e6065b9866fce62e75f1973 and the application crushes in the runtime (at program_manager.cpp). It's the time to debug.

[ghost]

I've pushed a new commit with changes in the spec. constant metadata generation, this works along with the changes from @steffenlarsen applied in commit 12d7c1f The idea is to skip undefined values during metadata IDs generation to let the padding processing handle such values as padding that they actually are.

[ghost]

/verify with intel/llvm-test-suite#830

[ghost]

Some tests failed but they are unrelated to the changes. The SYCL :: SpecConstants/vector-convolution-demo.cpp test added in intel/llvm-test-suite#830 passed.

[mlychkov]

Some tests failed but they are unrelated to the changes. The SYCL :: SpecConstants/vector-convolution-demo.cpp test added in intel/llvm-test-suite#830 passed.

Could you please check if failed tests have issues or create new ones for them?

[ghost]

@mlychkov I've created one and there already is one for another failure.

[ghost]

I would like to get a review from @steffenlarsen before merging. @steffenlarsen Could you have a look, please?

[steffenlarsen]

LGTM! It's a little confusing that ID has an ID member, but not enough that I worry about it.

[ghost]

I thought about it but didn't manage to make better naming.