[OpenCL] Allow blocks to capture arrays in OpenCL

[sidorovd]

Summary

Patch by Egor Churaev

[sidorovd]

Previously this patch was reviewed here: https://reviews.llvm.org/D26794 . I wasn't able to update it, so I created a new one with the comments applied.

[Anastasia]

LGTM! There is a small comment that can be addressed before the final commit. Thanks!

lib/Sema/SemaExpr.cpp

14627 ↗

(On Diff #164159)

It would be good to add spec reference here.

[sidorovd]

Reference to the Spec was added

cfe/trunk/lib/Sema/SemaExpr.cpp

static bool captureInBlock(BlockScopeInfo *BSI, VarDecl *Var,
                                  const bool BuildAndDiagnose,
                                  QualType &CaptureType,
                                  QualType &DeclRefType,
                                  const bool Nested,
                                  Sema &S) {
   Expr *CopyExpr = nullptr;
   bool ByRef = false;
 
-  // Blocks are not allowed to capture arrays.
-  if (CaptureType->isArrayType()) {
+  // Blocks are not allowed to capture arrays, excepting OpenCL.
+  // OpenCL v2.0 s1.12.5 (revision 40): arrays are captured by reference
+  // (decayed to pointers).
+  if (!S.getLangOpts().OpenCL && CaptureType->isArrayType()) {
     if (BuildAndDiagnose) {
       S.Diag(Loc, diag::err_ref_array_type);
       S.Diag(Var->getLocation(), diag::note_previous_decl)
       << Var->getDeclName();
     }
     return false;
   }
 

cfe/trunk/test/SemaOpenCL/block-array-capturing.cl

+// RUN: %clang_cc1 -O0 -cl-std=CL2.0 -triple spir64-unkown-unkown -emit-llvm %s -o -| FileCheck %s
+// expected-no-diagnostics
+
+typedef int (^block_t)();
+
+int block_typedef_kernel(global int* res) {
+  // CHECK: %{{.*}} = alloca <{ i32, i32, [3 x i32] }>
+  int a[3] = {1, 2, 3};
+  // CHECK: call void @llvm.memcpy{{.*}}
+  block_t b = ^() { return a[0]; };
+  return b();
+}
+
+// CHECK: define {{.*}} @__block_typedef_kernel_block_invoke
+// CHECK: %{{.*}} = getelementptr inbounds [3 x i32], [3 x i32] addrspace(4)* %{{.*}}, i64 0, i64 0
+// CHECK-NOT: call void @llvm.memcpy{{.*}}