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[SYCL] Disallow passing kernel by value for sycl_kernel attribute #15702

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[SYCL] Disallow passing kernel by value for sycl_kernel attribute #15702

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af03188
[SYCL] something deprecated attr propagation
AndreiZibrov Oct 15, 2024
1c5c2a4
Make error and fix test arguments
steffenlarsen Jul 29, 2025
3d724b4
Merge remote-tracking branch 'intel/sycl' into HEAD
steffenlarsen Jul 29, 2025
c1477b8
Fix formatting
steffenlarsen Jul 29, 2025
e5d1286
Merge remote-tracking branch 'intel/sycl' into HEAD
steffenlarsen Jul 29, 2025
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12 changes: 4 additions & 8 deletions clang/lib/Sema/SemaSYCL.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1122,18 +1122,14 @@ getKernelInvocationKind(FunctionDecl *KernelCallerFunc) {

// The SYCL kernel's 'object type' used for diagnostics and naming/mangling is
// the first parameter to a function template using the sycl_kernel
// attribute. In SYCL 1.2.1, this was passed by value,
// and in SYCL 2020, it is passed by reference.
// attribute. In SYCL 2020, this is passed by reference.
static QualType GetSYCLKernelObjectType(const FunctionDecl *KernelCaller) {
assert(KernelCaller->getNumParams() > 0 && "Insufficient kernel parameters");
QualType KernelParamTy = KernelCaller->getParamDecl(0)->getType();

// SYCL 2020 kernels are passed by reference.
if (KernelParamTy->isReferenceType())
KernelParamTy = KernelParamTy->getPointeeType();

// SYCL 1.2.1
return KernelParamTy.getUnqualifiedType();
assert(KernelParamTy->isReferenceType() && "Since SYCL 2020 kernels must be passed by reference.");
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I'm not a fan of the assert message. I think you can just say kernel must be passed by reference.

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I've changed it back. It seems like this assert gets hit before we issue a proper diagnostic for this kind of misuse.

return KernelParamTy = KernelParamTy->getPointeeType();
}

/// \return the target of given SYCL accessor type
Expand Down Expand Up @@ -5038,7 +5034,7 @@ void SemaSYCL::CheckSYCLKernelCall(FunctionDecl *KernelFunc,

// check that calling kernel conforms to spec
QualType KernelParamTy = KernelFunc->getParamDecl(0)->getType();
if (not KernelParamTy->isReferenceType()) {
if (! KernelParamTy->isReferenceType()) {
// passing by value. emit warning if using SYCL 2020 or greater
if (SemaRef.LangOpts.getSYCLVersion() >= LangOptions::SYCL_2020)
Diag(KernelFunc->getLocation(), diag::warn_sycl_pass_by_value_deprecated);
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If we still have a diagnostic for deprecation for this case, you cannot assert in GetSYCLKernelObjectType

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I've changed this to be an error. That said, even with it being an error, it is still checked later than the assert, so I am still on the side of no assertions.

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