[clang] 327c64c - [HIP][SPIRV] Implicit `new`/`delete` should be `cdecl` on host (#152023)

[via cfe-commits]

Author: Alex Voicu
Date: 2025-08-08T12:31:28-07:00
New Revision: 327c64cd6a69e35fe1351d4f5e89cd235e34ccc8

URL: https://github.com/llvm/llvm-project/commit/327c64cd6a69e35fe1351d4f5e89cd235e34ccc8
DIFF: https://github.com/llvm/llvm-project/commit/327c64cd6a69e35fe1351d4f5e89cd235e34ccc8.diff

LOG: [HIP][SPIRV] Implicit `new`/`delete` should be `cdecl` on host (#152023)

Client apps can (and in the case of the MSVC STL do) set cdecl
explicitly on `new` / `delete` implementations. On the other hand, Clang
generates implicit decls with the target's default CC. This is
problematic for SPIR-V, since the default there is spir_function, which
is not compatible. Since we cannot change pre-existing headers /
implementations, this patch sets the CC to C for the implicit host-side
decls, when compiling for device, to prevent the conflict. This is fine
because the host-side overloards do not get emitted on device.

Added: 
    clang/test/SemaHIP/amdgcnspirv-implicit-alloc-function-calling-conv.hip

Modified: 
    clang/lib/Sema/SemaExprCXX.cpp

Removed: 
    


################################################################################
diff  --git a/clang/lib/Sema/SemaExprCXX.cpp b/clang/lib/Sema/SemaExprCXX.cpp
index 0edfd6015cbd9..9c5554173d262 100644
--- a/clang/lib/Sema/SemaExprCXX.cpp
+++ b/clang/lib/Sema/SemaExprCXX.cpp
@@ -3497,6 +3497,19 @@ void Sema::DeclareGlobalAllocationFunction(DeclarationName Name,
   }
 
   auto CreateAllocationFunctionDecl = [&](Attr *ExtraAttr) {
+    // The MSVC STL has explicit cdecl on its (host-side) allocation function
+    // specializations for the allocation, so in order to prevent a CC clash
+    // we use the host's CC, if available, or CC_C as a fallback, for the
+    // host-side implicit decls, knowing these do not get emitted when compiling
+    // for device.
+    if (getLangOpts().CUDAIsDevice && ExtraAttr &&
+        isa<CUDAHostAttr>(ExtraAttr) &&
+        Context.getTargetInfo().getTriple().isSPIRV()) {
+      if (auto *ATI = Context.getAuxTargetInfo())
+        EPI.ExtInfo = EPI.ExtInfo.withCallingConv(ATI->getDefaultCallingConv());
+      else
+        EPI.ExtInfo = EPI.ExtInfo.withCallingConv(CallingConv::CC_C);
+    }
     QualType FnType = Context.getFunctionType(Return, Params, EPI);
     FunctionDecl *Alloc = FunctionDecl::Create(
         Context, GlobalCtx, SourceLocation(), SourceLocation(), Name, FnType,

diff  --git a/clang/test/SemaHIP/amdgcnspirv-implicit-alloc-function-calling-conv.hip b/clang/test/SemaHIP/amdgcnspirv-implicit-alloc-function-calling-conv.hip
new file mode 100644
index 0000000000000..c3e7e1a5cd59e
--- /dev/null
+++ b/clang/test/SemaHIP/amdgcnspirv-implicit-alloc-function-calling-conv.hip
@@ -0,0 +1,32 @@
+// RUN: %clang_cc1 %s -fcuda-is-device -std=c++17 -triple spirv32 -verify
+// RUN: %clang_cc1 %s -fcuda-is-device -std=c++17 -triple spirv64 -verify
+// RUN: %clang_cc1 %s -fcuda-is-device -std=c++17 -triple spirv64-amd-amdhsa -verify
+// RUN: %clang_cc1 %s -fcuda-is-device -std=c++17 -triple spirv32 -aux-triple x86_64-unknown-linux-gnu -verify
+// RUN: %clang_cc1 %s -fcuda-is-device -std=c++17 -triple spirv64 -aux-triple x86_64-unknown-linux-gnu -verify
+// RUN: %clang_cc1 %s -fcuda-is-device -std=c++17 -triple spirv64-amd-amdhsa -aux-triple x86_64-unknown-linux-gnu -verify
+// RUN: %clang_cc1 %s -fcuda-is-device -std=c++17 -triple spirv32 -aux-triple x86_64-pc-windows-msvc -verify
+// RUN: %clang_cc1 %s -fcuda-is-device -std=c++17 -triple spirv64 -aux-triple x86_64-pc-windows-msvc -verify
+// RUN: %clang_cc1 %s -fcuda-is-device -std=c++17 -triple spirv64-amd-amdhsa -aux-triple x86_64-pc-windows-msvc -verify
+
+// expected-no-diagnostics
+
+namespace std
+{
+    enum class align_val_t : __SIZE_TYPE__ {};
+    struct nothrow_t { explicit nothrow_t() = default; };
+    extern nothrow_t const nothrow;
+}
+
+void* __attribute__((cdecl)) operator new(__SIZE_TYPE__);
+void* __attribute__((cdecl)) operator new[](__SIZE_TYPE__);
+void* __attribute__((cdecl)) operator new(__SIZE_TYPE__, ::std::align_val_t);
+void* __attribute__((cdecl)) operator new[](__SIZE_TYPE__, ::std::align_val_t);
+
+void __attribute__((cdecl)) operator delete(void*) noexcept;
+void __attribute__((cdecl)) operator delete[](void*) noexcept;
+void __attribute__((cdecl)) operator delete(void*, __SIZE_TYPE__) noexcept;
+void __attribute__((cdecl)) operator delete[](void*, __SIZE_TYPE__) noexcept;
+void __attribute__((cdecl)) operator delete(void*, ::std::align_val_t) noexcept;
+void __attribute__((cdecl)) operator delete[](void*, ::std::align_val_t) noexcept;
+void __attribute__((cdecl)) operator delete(void*, __SIZE_TYPE__, ::std::align_val_t) noexcept;
+void __attribute__((cdecl)) operator delete[](void*, __SIZE_TYPE__, ::std::align_val_t) noexcept;