From c3cd84365e099ab6dfa4b484475ef66f33f16eab Mon Sep 17 00:00:00 2001
From: TB Schardl <neboat@mit.edu>
Date: Sat, 30 Nov 2024 09:13:46 -0500
Subject: [PATCH] [SemaExpr] Fix hyperobject-lookup lvalue conversion involving
 qualifiers and xvalues.

---
 clang/lib/AST/Type.cpp                        |  3 +-
 clang/lib/Sema/SemaExpr.cpp                   |  2 +-
 .../Cilk/hyper-lookup-lvalue-conversion.cpp   | 57 +++++++++++++++++++
 3 files changed, 60 insertions(+), 2 deletions(-)
 create mode 100644 clang/test/Cilk/hyper-lookup-lvalue-conversion.cpp

diff --git a/clang/lib/AST/Type.cpp b/clang/lib/AST/Type.cpp
index fee3f1f3319f..8a1253ed17e8 100644
--- a/clang/lib/AST/Type.cpp
+++ b/clang/lib/AST/Type.cpp
@@ -3416,7 +3416,8 @@ QualType QualType::getNonLValueExprType(const ASTContext &Context) const {
 
 QualType QualType::stripHyperobject() const {
   if (const auto *Hyperobject = getTypePtr()->getAs<HyperobjectType>())
-    return Hyperobject->getElementType();
+    return Hyperobject->getElementType().withFastQualifiers(
+        getLocalFastQualifiers());
   return *this;
 }
 
diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
index 4f99e34d18b5..ca033b097613 100644
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -2279,7 +2279,7 @@ NonOdrUseReason Sema::getNonOdrUseReasonInCurrentContext(ValueDecl *D) {
 }
 
 Expr *Sema::BuildHyperobjectLookup(Expr *E, bool Pointer) {
-  if (!Pointer && !E->isLValue())
+  if (!Pointer && !E->isGLValue())
     return E;
 
   if (getLangOpts().getCilk() != LangOptions::Cilk_opencilk)
diff --git a/clang/test/Cilk/hyper-lookup-lvalue-conversion.cpp b/clang/test/Cilk/hyper-lookup-lvalue-conversion.cpp
new file mode 100644
index 000000000000..36ff0ce5af92
--- /dev/null
+++ b/clang/test/Cilk/hyper-lookup-lvalue-conversion.cpp
@@ -0,0 +1,57 @@
+// Check unusual lvalue conversions involving hyperobject lookups, qualifiers, and xvalues.
+//
+// RUN: %clang_cc1 %s -x c++ -fopencilk -verify -S -emit-llvm -disable-llvm-passes -o - | FileCheck %s
+// expected-no-diagnostics
+
+// Simplified version of std::move for standalone test.
+namespace std {
+template <typename T>
+T &&move(T &obj) {
+  return static_cast<T &&>(obj);
+}
+}
+
+// Reducer definition.
+template <typename T> void sum_init(void *v) { *reinterpret_cast<T *>(v) = T{}; }
+
+template <typename T> void sum_reduce(void *v, void *v2) {
+  T *a = reinterpret_cast<T *>(v), *b = reinterpret_cast<T *>(v2);
+  *a += *b;
+}
+
+template <typename T> using SumReducer = T _Hyperobject(sum_init<T>, sum_reduce<T>);
+
+using Real = double;
+
+void h(Real arg);
+
+template <typename T>
+void g(const T &arg) { h(arg); }
+
+template <typename T>
+void f(T&& arg) { h(std::move(arg)); }
+
+void run() {
+  SumReducer<Real> sumAParRelError = 0;
+  // Check handling of hyperobject lookup when result requires extra const qualifier.
+  g(sumAParRelError);
+  // Check handling of hyperobject lookup when result treated as xvalue.
+  f(sumAParRelError);
+}
+
+// CHECK-LABEL: define {{.*}}void @_Z3runv()
+// CHECK: %[[SUMAPARRELERROR:.+]] = alloca double
+// CHECK: call void @llvm.reducer.register.i64(ptr %[[SUMAPARRELERROR]]
+// CHECK-NEXT: call void @_Z1gIHdEvRKT_(ptr {{.*}}%[[SUMAPARRELERROR]])
+// CHECK-NEXT: call void @_Z1fIRHdEvOT_(ptr {{.*}}%[[SUMAPARRELERROR]])
+// CHECK-NEXT: call void @llvm.reducer.unregister(ptr %sumAParRelError)
+
+// CHECK-LABEL: define {{.*}}void @_Z1gIHdEvRKT_(ptr
+// CHECK: %[[LOOKUP:.+]] = call ptr @llvm.hyper.lookup.i64(ptr
+// CHECK-NEXT: %[[VIEW:.+]] = load double, ptr %[[LOOKUP]]
+// CHECK-NEXT: call void @_Z1hd(double {{.*}}%[[VIEW]])
+
+// CHECK-LABEL: define {{.*}}void @_Z1fIRHdEvOT_(ptr
+// CHECK: %[[LOOKUP:.+]] = call ptr @llvm.hyper.lookup.i64(ptr
+// CHECK-NEXT: %[[VIEW:.+]] = load double, ptr %[[LOOKUP]]
+// CHECK-NEXT: call void @_Z1hd(double {{.*}}%[[VIEW]])