[clang] [OpenCL] Suppress -Wreturn-stack-address for function-scope local variable (PR #181602)

[via cfe-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang

Author: Wenju He (wenju-he)

<details>
<summary>Changes</summary>

when __cl_clang_function_scope_local_variables extension is enabled.

OpenCL local variable has lifetime of work-group, not function call stack.

---
Full diff: https://github.com/llvm/llvm-project/pull/181602.diff


2 Files Affected:

- (modified) clang/lib/Sema/CheckExprLifetime.cpp (+7) 
- (added) clang/test/SemaOpenCL/function-scope-local-return.cl (+13) 


``````````diff
diff --git a/clang/lib/Sema/CheckExprLifetime.cpp b/clang/lib/Sema/CheckExprLifetime.cpp
index 5d4b4508541b7..c2f2aa8fc9487 100644
--- a/clang/lib/Sema/CheckExprLifetime.cpp
+++ b/clang/lib/Sema/CheckExprLifetime.cpp
@@ -1337,6 +1337,13 @@ checkExprLifetimeImpl(Sema &SemaRef, const InitializedEntity *InitEntity,
         // expression.
         if (LK == LK_StmtExprResult)
           return false;
+        if (auto *VD = dyn_cast<VarDecl>(DRE->getDecl())) {
+          if (VD->getType().getAddressSpace() == LangAS::opencl_local &&
+              SemaRef.getOpenCLOptions().isAvailableOption(
+                  "__cl_clang_function_scope_local_variables",
+                  SemaRef.getLangOpts()))
+            return false;
+        }
         SemaRef.Diag(DiagLoc, diag::warn_ret_stack_addr_ref)
             << InitEntity->getType()->isReferenceType() << DRE->getDecl()
             << isa<ParmVarDecl>(DRE->getDecl()) << (LK == LK_MustTail)
diff --git a/clang/test/SemaOpenCL/function-scope-local-return.cl b/clang/test/SemaOpenCL/function-scope-local-return.cl
new file mode 100644
index 0000000000000..1de86b4293a9a
--- /dev/null
+++ b/clang/test/SemaOpenCL/function-scope-local-return.cl
@@ -0,0 +1,13 @@
+// RUN: %clang_cc1 %s -verify -pedantic -fsyntax-only -cl-std=CL3.0
+
+// Check returning a pointer to a local address space variable does not warn
+// if __cl_clang_function_scope_local_variables extension is enabled.
+
+// expected-no-diagnostics
+
+#pragma OPENCL EXTENSION __cl_clang_function_scope_local_variables : enable
+
+local int* get_group_scratch() {
+  local int data[64];
+  return data;
+}

``````````

</details>


https://github.com/llvm/llvm-project/pull/181602