[SYCL][CMake] Enable LLVM_LINK_LLVM_DYLIB builds of the SYCL toolchain

[koparasy]

Enable building the SYCL toolchain with -DLLVM_LINK_LLVM_DYLIB=ON
(-DCLANG_LINK_CLANG_DYLIB=ON), previously unsupported.

This is a needed change to allow clang plugins to be loaded during compilation
of sycl code.

Under dylib, tools link libLLVM.so instead of the LLVM component
libraries and so don't inherit their INTERFACE properties. Fixes:

• Bump the vc-intrinsics pin to 0c3296b, which drops a spurious LLVMGenXIntrinsics
  dependency on LLVMSPIRVLib that formed an illegal cross-dylib cycle
  (LLVM -> SYCLLowerIR -> GenXIntrinsics -> SPIRVLib
  -> LLVM) and broke CMake configuration.
• LLVMSPIRVLib is not part of libLLVM.so: link it explicitly in
  spirv-to-ir-wrapper and sycl-jit (matching llvm-spirv).
• sycl-post-link and sycl-jit include vc-intrinsics headers; add the
  LLVMGenXIntrinsics INTERFACE include directories explicitly.

All changes are guarded by LLVM_LINK_LLVM_DYLIB; static builds are
unchanged.

[koparasy]

@vmustya for your verifier.

[koparasy]

@intel/llvm-reviewers-runtime @intel/dpcpp-tools-reviewers @intel/dpcpp-esimd-reviewers can you please review?

[YuriPlyakhin]

Is there a CI coverage for the configuration this PR enables?

I have not found LLVM_LINK_LLVM_DYLIB=ON under .github/workflows/ or in buildbot/configure.py.

Could you please add a --llvm-link-dylib-style switch to buildbot/configure.py and a nightly job (or even less frequent would be fine)?

[YuriPlyakhin]

• drops a spurious
  LLVMSPIRVLib dependency on LLVMGenXIntrinsics

did you mean:
drops a spurious LLVMGenXIntrinsics dependency on LLVMSPIRVLib
?

[koparasy]

Is there a CI coverage for the configuration this PR enables?

I have not found LLVM_LINK_LLVM_DYLIB=ON under .github/workflows/ or in buildbot/configure.py.

Could you please add a --llvm-link-dylib-style switch to buildbot/configure.py and a nightly job (or even less frequent would be fine)?

Done in 0de19b2

[koparasy]

This looks to me as the common pattern in nightly, see https://github.com/intel/llvm/pull/23052/changes#diff-f8dae70b8775cf9c5fb547e9210ddc33d1e878401bfcf752b4fbdf16b1b601bbL55 . Can anyone verify that we can ignore this warning?

[KornevNikita]

yeah let's ignore this

[KornevNikita]

nightly changes lgtm

[koparasy]

@intel/dpcpp-esimd-reviewers can you please review this. Thank you!

[YuriPlyakhin]

Is this line necessary (DCLANG_LINK_CLANG_DYLIB)?

Please, check:

llvm/clang/CMakeLists.txt

Line 357 in bf6137c

set(CLANG_LINK_CLANG_DYLIB ${LLVM_LINK_LLVM_DYLIB} CACHE BOOL

[koparasy]

I believe what I have is more robust. If cmakelist.txt is modified (unlikely), I still want both of them to be enabled to test our build.

Do you want me to modify and skip the setting?

[YuriPlyakhin]

I want to avoid side effects.

Example (I did not verify it though):

On Windows, CAN_BUILD_LLVM_DYLIB is OFF for MSVC, so cmake_dependent_option force-sets LLVM_LINK_LLVM_DYLIB=OFF:

llvm/llvm/CMakeLists.txt

Lines 977 to 983 in c2098bb

	set(CAN_BUILD_LLVM_DYLIB OFF)
	if(NOT MSVC OR LLVM_BUILD_LLVM_DYLIB_VIS)
	set(CAN_BUILD_LLVM_DYLIB ON)
	endif()
	cmake_dependent_option(LLVM_LINK_LLVM_DYLIB "Link tools against the libllvm dynamic library" OFF
	"CAN_BUILD_LLVM_DYLIB" OFF)

Explicit -DCLANG_LINK_CLANG_DYLIB=ON seems to result in error in the case, when 2 settings do not match:

llvm/clang/CMakeLists.txt

Lines 360 to 363 in bf6137c

	if (NOT LLVM_LINK_LLVM_DYLIB AND CLANG_LINK_CLANG_DYLIB)
	message(FATAL_ERROR "Cannot set CLANG_LINK_CLANG_DYLIB=ON when "
	"LLVM_LINK_LLVM_DYLIB=OFF")
	endif()

[YuriPlyakhin]

But I let @intel/dpcpp-devops-reviewers make a decision, they own this configuration file.

[YuriPlyakhin]

changes in llvm LGTM