[clang] [clang] Fallback to C calling convention for sycl_kernel attribute (PR #161349)

[via cfe-commits]

https://github.com/camc updated https://github.com/llvm/llvm-project/pull/161349

>From acaf93238a19bfbe6b6e1a6be59673691564305d Mon Sep 17 00:00:00 2001
From: camc <pushy-crop-cartel at duck.com>
Date: Tue, 30 Sep 2025 10:22:42 +0000
Subject: [PATCH 1/2] [clang] Fallback to C callingconv for sycl_kernel
 attribute. (#GH161077)

---
 clang/docs/ReleaseNotes.rst      | 1 +
 clang/lib/CodeGen/TargetInfo.cpp | 3 ++-
 clang/test/CodeGen/sycl-kernel.c | 5 +++++
 3 files changed, 8 insertions(+), 1 deletion(-)
 create mode 100644 clang/test/CodeGen/sycl-kernel.c

diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index e8deae50e4cb0..74580b77353d5 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -397,6 +397,7 @@ Bug Fixes to Attribute Support
 - Using ``[[gnu::cleanup(some_func)]]`` where some_func is annotated with
   ``[[gnu::error("some error")]]`` now correctly triggers an error. (#GH146520)
 - Fix a crash when the function name is empty in the `swift_name` attribute. (#GH157075)
+- Fix a crash when the ``sycl_kernel`` attribute is used while not compiling OpenCL (#GH161077).
 
 Bug Fixes to C++ Support
 ^^^^^^^^^^^^^^^^^^^^^^^^
diff --git a/clang/lib/CodeGen/TargetInfo.cpp b/clang/lib/CodeGen/TargetInfo.cpp
index 1e58c3f217812..4ff847f4f6ff6 100644
--- a/clang/lib/CodeGen/TargetInfo.cpp
+++ b/clang/lib/CodeGen/TargetInfo.cpp
@@ -123,8 +123,9 @@ unsigned TargetCodeGenInfo::getDeviceKernelCallingConv() const {
     // conventions; different targets might split structs passed as values
     // to multiple function arguments etc.
     return llvm::CallingConv::SPIR_KERNEL;
+  } else {
+    return llvm::CallingConv::C;
   }
-  llvm_unreachable("Unknown kernel calling convention");
 }
 
 void TargetCodeGenInfo::setOCLKernelStubCallingConvention(
diff --git a/clang/test/CodeGen/sycl-kernel.c b/clang/test/CodeGen/sycl-kernel.c
new file mode 100644
index 0000000000000..77410e5a216ff
--- /dev/null
+++ b/clang/test/CodeGen/sycl-kernel.c
@@ -0,0 +1,5 @@
+// RUN: %clang_cc1 -emit-llvm %s -o /dev/null
+
+__attribute__((sycl_kernel)) void foo(int *ret) {
+  *ret = 1;
+}

>From 31efdd2449637fbb9d21ddbadbe09bb22301f7ff Mon Sep 17 00:00:00 2001
From: c <c>
Date: Tue, 30 Sep 2025 22:54:15 +0000
Subject: [PATCH 2/2] Ignore device_kernel when not compiling OpenCL or CUDA

---
 clang/docs/ReleaseNotes.rst      | 2 +-
 clang/lib/CodeGen/TargetInfo.cpp | 3 +--
 clang/lib/Sema/SemaDeclAttr.cpp  | 4 +++-
 clang/lib/Sema/SemaType.cpp      | 2 +-
 4 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 74580b77353d5..e02509da7b06a 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -397,7 +397,7 @@ Bug Fixes to Attribute Support
 - Using ``[[gnu::cleanup(some_func)]]`` where some_func is annotated with
   ``[[gnu::error("some error")]]`` now correctly triggers an error. (#GH146520)
 - Fix a crash when the function name is empty in the `swift_name` attribute. (#GH157075)
-- Fix a crash when the ``sycl_kernel`` attribute is used while not compiling OpenCL (#GH161077).
+- Fix a crash when ``device_kernel`` attributes are used outside OpenCL/CUDA (#GH161077).
 
 Bug Fixes to C++ Support
 ^^^^^^^^^^^^^^^^^^^^^^^^
diff --git a/clang/lib/CodeGen/TargetInfo.cpp b/clang/lib/CodeGen/TargetInfo.cpp
index 4ff847f4f6ff6..1e58c3f217812 100644
--- a/clang/lib/CodeGen/TargetInfo.cpp
+++ b/clang/lib/CodeGen/TargetInfo.cpp
@@ -123,9 +123,8 @@ unsigned TargetCodeGenInfo::getDeviceKernelCallingConv() const {
     // conventions; different targets might split structs passed as values
     // to multiple function arguments etc.
     return llvm::CallingConv::SPIR_KERNEL;
-  } else {
-    return llvm::CallingConv::C;
   }
+  llvm_unreachable("Unknown kernel calling convention");
 }
 
 void TargetCodeGenInfo::setOCLKernelStubCallingConvention(
diff --git a/clang/lib/Sema/SemaDeclAttr.cpp b/clang/lib/Sema/SemaDeclAttr.cpp
index a8dfa4d7df2d5..74fd5d89f3db7 100644
--- a/clang/lib/Sema/SemaDeclAttr.cpp
+++ b/clang/lib/Sema/SemaDeclAttr.cpp
@@ -5204,7 +5204,9 @@ static void handleCallConvAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
 static void handleDeviceKernelAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
   const auto *FD = dyn_cast_or_null<FunctionDecl>(D);
   bool IsFunctionTemplate = FD && FD->getDescribedFunctionTemplate();
-  if (S.getLangOpts().SYCLIsDevice) {
+  if (!S.getLangOpts().OpenCL && !S.getLangOpts().CUDA) {
+    S.Diag(AL.getLoc(), diag::warn_attribute_ignored) << AL;
+  } else if (S.getLangOpts().SYCLIsDevice) {
     if (!IsFunctionTemplate) {
       S.Diag(AL.getLoc(), diag::warn_attribute_wrong_decl_type_str)
           << AL << AL.isRegularKeywordAttribute() << "function templates";
diff --git a/clang/lib/Sema/SemaType.cpp b/clang/lib/Sema/SemaType.cpp
index bee613aa5f1c5..aaa92b238376c 100644
--- a/clang/lib/Sema/SemaType.cpp
+++ b/clang/lib/Sema/SemaType.cpp
@@ -3780,7 +3780,7 @@ static CallingConv getCCForDeclaratorChunk(
       }
     }
   }
-  if (!S.getLangOpts().isSYCL()) {
+  if (S.getLangOpts().OpenCL || S.getLangOpts().CUDA) {
     for (const ParsedAttr &AL : D.getDeclSpec().getAttributes()) {
       if (AL.getKind() == ParsedAttr::AT_DeviceKernel) {
         CC = CC_DeviceKernel;