[clang] [CUDA][HIP] Fix implicit attribute of builtin (PR #138162)

[Yaxun Liu via cfe-commits]

https://github.com/yxsamliu created https://github.com/llvm/llvm-project/pull/138162

When a builtin function with generic pointer parameter is passed a pointer with address space, clang creates an overloaded builtin function but does not make it implicit. This causes error when the builtin is called by device functions since CUDA/HIP relies on the implicit attribute to treat a builtin function as callable on both host and device sides.

Fixed by making the created overloaded builtin functions implicit.

>From 9c73c14588c64623bfa6bcb4fd11e6e12dc0745e Mon Sep 17 00:00:00 2001
From: "Yaxun (Sam) Liu" <yaxun.liu at amd.com>
Date: Thu, 1 May 2025 12:08:05 -0400
Subject: [PATCH] [CUDA][HIP] Fix implicit attribute of builtin

When a builtin function with generic pointer parameter is passed
a pointer with address space, clang creates an overloaded
builtin function but does not make it implicit. This causes
error when the builtin is called by device functions
since CUDA/HIP relies on the implicit attribute to treat
a builtin function as callable on both host and device
sides.

Fixed by making the created overloaded builtin functions implicit.
---
 clang/lib/Sema/SemaExpr.cpp               |  1 +
 clang/test/SemaCUDA/overloaded-builtin.cu | 23 +++++++++++++++++++++++
 2 files changed, 24 insertions(+)
 create mode 100644 clang/test/SemaCUDA/overloaded-builtin.cu

diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
index 0cd86dc54b0ab..d9eccb31e6d1e 100644
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -6358,6 +6358,7 @@ static FunctionDecl *rewriteBuiltinFunctionDecl(Sema *Sema, ASTContext &Context,
   }
   OverloadDecl->setParams(Params);
   Sema->mergeDeclAttributes(OverloadDecl, FDecl);
+  OverloadDecl->setImplicit(true);
   return OverloadDecl;
 }
 
diff --git a/clang/test/SemaCUDA/overloaded-builtin.cu b/clang/test/SemaCUDA/overloaded-builtin.cu
new file mode 100644
index 0000000000000..719bfea4aef2f
--- /dev/null
+++ b/clang/test/SemaCUDA/overloaded-builtin.cu
@@ -0,0 +1,23 @@
+// expected-no-diagnostics
+
+// RUN: %clang_cc1 -triple x86_64-unknown-linux-gnu -aux-triple amdgcn-amd-amdhsa -fsyntax-only -verify -xhip %s
+// RUN: %clang_cc1 -triple amdgcn-amd-amdhsa -fsyntax-only -fcuda-is-device -verify -xhip %s
+
+#include "Inputs/cuda.h"
+
+__global__ void kernel() {                         
+  __attribute__((address_space(0))) void *mem_ptr;
+  (void)__builtin_amdgcn_is_shared(mem_ptr);
+}
+
+template<typename T>
+__global__ void template_kernel(T *p) {                         
+  __attribute__((address_space(0))) void *mem_ptr;
+  (void)__builtin_amdgcn_is_shared(mem_ptr);
+}
+
+int main() {
+  int *p;
+  kernel<<<1,1>>>();
+  template_kernel<<<1,1>>>(p);
+}