__c11_atomic_load's _Atomic can be const

Summary:
C++11 onwards specs the non-member functions atomic_load and atomic_load_explicit as taking the atomic<T> by const (potentially volatile) pointer. C11, in its infinite wisdom, decided to drop the const, and C17 will fix this with DR459 (the current draft forgot to fix B.16, but that’s not the normative part).

clang’s lib/Headers/stdatomic.h implements these as #define to the __c11_* equivalent, which are builtins with custom typecheck. Fix the typecheck.

D47613 takes care of the libc++ side.

Discussion: http://lists.llvm.org/pipermail/cfe-dev/2018-May/058129.html

<rdar://problem/27426936>

Reviewers: rsmith

Subscribers: cfe-commits

Differential Revision: https://reviews.llvm.org/D47618

llvm-svn: 338743

3 files changed, 6 insertions, 5 deletions

diff --git a/clang/lib/Sema/SemaChecking.cpp b/clang/lib/Sema/SemaChecking.cpp
index 93dbeab5b03..2edc9ca0d7d 100644
--- a/clang/lib/Sema/SemaChecking.cpp
+++ b/clang/lib/Sema/SemaChecking.cpp
@@ -4347,7 +4347,7 @@ ExprResult Sema::SemaAtomicOpsOverloaded(ExprResult TheCallResult,
         << Ptr->getType() << Ptr->getSourceRange();
       return ExprError();
     }
-    if (AtomTy.isConstQualified() ||
+    if ((Form != Load && Form != LoadCopy && AtomTy.isConstQualified()) ||
         AtomTy.getAddressSpace() == LangAS::opencl_constant) {
       Diag(DRE->getLocStart(), diag::err_atomic_op_needs_non_const_atomic)
           << (AtomTy.isConstQualified() ? 0 : 1) << Ptr->getType()
diff --git a/clang/test/Sema/atomic-ops.c b/clang/test/Sema/atomic-ops.c
index 49310bf45b6..638c30f278c 100644
--- a/clang/test/Sema/atomic-ops.c
+++ b/clang/test/Sema/atomic-ops.c
@@ -115,7 +115,7 @@ void f(_Atomic(int) *i, const _Atomic(int) *ci,
   __c11_atomic_load(i, memory_order_seq_cst);
   __c11_atomic_load(p, memory_order_seq_cst);
   __c11_atomic_load(d, memory_order_seq_cst);
-  __c11_atomic_load(ci, memory_order_seq_cst); // expected-error {{address argument to atomic operation must be a pointer to non-const _Atomic type ('const _Atomic(int) *' invalid)}}
+  __c11_atomic_load(ci, memory_order_seq_cst);
 
   int load_n_1 = __atomic_load_n(I, memory_order_relaxed);
   int *load_n_2 = __atomic_load_n(P, memory_order_relaxed);
@@ -222,7 +222,7 @@ void f(_Atomic(int) *i, const _Atomic(int) *ci,
 
   __c11_atomic_init(ci, 0); // expected-error {{address argument to atomic operation must be a pointer to non-const _Atomic type ('const _Atomic(int) *' invalid)}}
   __c11_atomic_store(ci, 0, memory_order_release); // expected-error {{address argument to atomic operation must be a pointer to non-const _Atomic type ('const _Atomic(int) *' invalid)}}
-  __c11_atomic_load(ci, memory_order_acquire); // expected-error {{address argument to atomic operation must be a pointer to non-const _Atomic type ('const _Atomic(int) *' invalid)}}
+  __c11_atomic_load(ci, memory_order_acquire);
 
   // Ensure the <stdatomic.h> macros behave appropriately.
   atomic_int n = ATOMIC_VAR_INIT(123);
diff --git a/clang/test/SemaOpenCL/atomic-ops.cl b/clang/test/SemaOpenCL/atomic-ops.cl
index 2ec6cde2117..540520d4e32 100644
--- a/clang/test/SemaOpenCL/atomic-ops.cl
+++ b/clang/test/SemaOpenCL/atomic-ops.cl
@@ -58,7 +58,8 @@ void f(atomic_int *i, const atomic_int *ci,
   __opencl_atomic_load(i, memory_order_seq_cst, memory_scope_work_group);
   __opencl_atomic_load(p, memory_order_seq_cst, memory_scope_work_group);
   __opencl_atomic_load(d, memory_order_seq_cst, memory_scope_work_group);
-  __opencl_atomic_load(ci, memory_order_seq_cst, memory_scope_work_group); // expected-error {{address argument to atomic operation must be a pointer to non-const _Atomic type ('const __generic atomic_int *' (aka 'const __generic _Atomic(int) *') invalid)}}
+  __opencl_atomic_load(ci, memory_order_seq_cst, memory_scope_work_group);
+  __opencl_atomic_load(i_c, memory_order_seq_cst, memory_scope_work_group); // expected-error {{address argument to atomic operation must be a pointer to non-constant _Atomic type ('__constant atomic_int *' (aka '__constant _Atomic(int) *') invalid)}}
 
   __opencl_atomic_store(i, 1, memory_order_seq_cst, memory_scope_work_group);
   __opencl_atomic_store(p, 1, memory_order_seq_cst, memory_scope_work_group);
@@ -94,7 +95,7 @@ void f(atomic_int *i, const atomic_int *ci,
 
   __opencl_atomic_init(ci, 0); // expected-error {{address argument to atomic operation must be a pointer to non-const _Atomic type ('const __generic atomic_int *' (aka 'const __generic _Atomic(int) *') invalid)}}
   __opencl_atomic_store(ci, 0, memory_order_release, memory_scope_work_group); // expected-error {{address argument to atomic operation must be a pointer to non-const _Atomic type ('const __generic atomic_int *' (aka 'const __generic _Atomic(int) *') invalid)}}
-  __opencl_atomic_load(ci, memory_order_acquire, memory_scope_work_group); // expected-error {{address argument to atomic operation must be a pointer to non-const _Atomic type ('const __generic atomic_int *' (aka 'const __generic _Atomic(int) *') invalid)}}
+  __opencl_atomic_load(ci, memory_order_acquire, memory_scope_work_group);
 
   __opencl_atomic_init(&gn, 456);
   __opencl_atomic_init(&gn, (void*)0); // expected-warning{{incompatible pointer to integer conversion passing '__generic void *' to parameter of type 'int'}}