[OpenCL] Fix serialization of OpenCLExtensionDecls

Summary:
I recently discovered that adding the following code into `opencl-c.h` causes
failure of `test/Headers/opencl-c-header.cl`:
```
#pragma OPENCL EXTENSION cl_my_ext : begin
void cl_my_ext_foobarbaz();
#pragma OPENCL EXTENSIOn cl_my_ext : end
```

Clang crashes at the assertion is `ASTReader::getGlobalSubmoduleID()`:
```
assert(I != M.SubmoduleRemap.end() && "Invalid index into submodule index remap");
```

The root cause of the problem that to deserialize `OPENCL_EXTENSION_DECLS`
section `ASTReader` needs to deserialize a Decl contained in it. In turn,
deserializing a Decl requires information about whether this declaration is
part of a (sub)module, but this information is not read yet because it is
located further in a module file.

Reviewers: Anastasia, yaxunl, JDevlieghere

Reviewed By: Anastasia

Subscribers: sidorovd, cfe-commits, asavonic

Differential Revision: https://reviews.llvm.org/D53200

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@345497 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Serialization/ASTWriter.cpp

@@ -5014,13 +5014,16 @@ ASTFileSignature ASTWriter::WriteASTCore(Sema &SemaRef, StringRef isysroot,
   WriteFPPragmaOptions(SemaRef.getFPOptions());
   WriteOpenCLExtensions(SemaRef);
   WriteOpenCLExtensionTypes(SemaRef);
-  WriteOpenCLExtensionDecls(SemaRef);
   WriteCUDAPragmas(SemaRef);
 
   // If we're emitting a module, write out the submodule information.
   if (WritingModule)
     WriteSubmodules(WritingModule);
 
+  // We need to have information about submodules to correctly deserialize
+  // decls from OpenCLExtensionDecls block
+  WriteOpenCLExtensionDecls(SemaRef);
+
   Stream.EmitRecord(SPECIAL_TYPES, SpecialTypes);
 
   // Write the record containing external, unnamed definitions.

test/SemaOpenCL/extension-begin.cl

@@ -1,37 +1,29 @@
 // Test this without pch.
-// RUN: %clang_cc1 %s -DHEADER -DHEADER_USER -triple spir-unknown-unknown -verify -pedantic -fsyntax-only
+// RUN: %clang_cc1 %s -triple spir-unknown-unknown -verify -pedantic -fsyntax-only
 
 // Test with pch.
-// RUN: %clang_cc1 %s -DHEADER -triple spir-unknown-unknown -emit-pch -o %t -verify -pedantic
-// RUN: %clang_cc1 %s -DHEADER_USER -triple spir-unknown-unknown -include-pch %t -fsyntax-only -verify -pedantic
-
-#if defined(HEADER) && !defined(INCLUDED)
-#define INCLUDED 
-
-#pragma OPENCL EXTENSION all : begin // expected-warning {{expected 'disable' - ignoring}}
-#pragma OPENCL EXTENSION all : end // expected-warning {{expected 'disable' - ignoring}}
-
-#pragma OPENCL EXTENSION my_ext : begin 
-
-struct A {
-  int a;
-};
-
-typedef struct A TypedefOfA;
-typedef const TypedefOfA* PointerOfA;
-
-void f(void);
-
-__attribute__((overloadable)) void g(long x);
-
-#pragma OPENCL EXTENSION my_ext : end
-#pragma OPENCL EXTENSION my_ext : end // expected-warning {{OpenCL extension end directive mismatches begin directive - ignoring}}
-
-__attribute__((overloadable)) void g(void);
-
-#endif // defined(HEADER) && !defined(INCLUDED)
-
-#ifdef HEADER_USER
+// RUN: %clang_cc1 -x cl %S/extension-begin.h -triple spir-unknown-unknown -emit-pch -o %t.pch -pedantic
+// RUN: %clang_cc1 %s -triple spir-unknown-unknown -include-pch %t.pch -DIMPLICIT_INCLUDE -DUSE_PCH -fsyntax-only -verify -pedantic
+
+// Test with modules
+// RUN: rm -rf %t.modules
+// RUN: mkdir -p %t.modules
+//
+// RUN: %clang_cc1 -cl-std=CL1.2 -DIMPLICIT_INCLUDE -include %S/extension-begin.h -triple spir-unknown-unknown -O0 -emit-llvm -o - -fmodules -fimplicit-module-maps -fmodules-cache-path=%t.modules %s -verify -pedantic
+//
+// RUN: rm -rf %t.modules
+// RUN: mkdir -p %t.modules
+//
+// RUN: %clang_cc1 -cl-std=CL2.0 -DIMPLICIT_INCLUDE -include %S/extension-begin.h -triple spir-unknown-unknown -O0 -emit-llvm -o - -fmodules -fimplicit-module-maps -fmodules-cache-path=%t.modules %s -verify -pedantic
+
+#ifndef IMPLICIT_INCLUDE
+#include "extension-begin.h"
+#endif // IMPLICIT_INCLUDE
+#ifndef USE_PCH
+// expected-warning@extension-begin.h:4 {{expected 'disable' - ignoring}}
+// expected-warning@extension-begin.h:5 {{expected 'disable' - ignoring}}
+// expected-warning@extension-begin.h:21 {{OpenCL extension end directive mismatches begin directive - ignoring}}
+#endif // USE_PCH
 
 #pragma OPENCL EXTENSION my_ext : enable
 void test_f1(void) {
@@ -48,9 +40,7 @@ void test_f2(void) {
   PointerOfA test_A_pointer; // expected-error {{use of type 'PointerOfA' (aka 'const struct A *') requires my_ext extension to be enabled}}
   f(); // expected-error {{use of declaration 'f' requires my_ext extension to be enabled}}
   g(0); // expected-error {{no matching function for call to 'g'}}
-        // expected-note@-26 {{candidate unavailable as it requires OpenCL extension 'my_ext' to be disabled}}
-        // expected-note@-22 {{candidate function not viable: requires 0 arguments, but 1 was provided}}
+        // expected-note@extension-begin.h:18 {{candidate unavailable as it requires OpenCL extension 'my_ext' to be disabled}}
+        // expected-note@extension-begin.h:23 {{candidate function not viable: requires 0 arguments, but 1 was provided}}
 }
 
-#endif // HEADER_USER
-

test/SemaOpenCL/extension-begin.h

@@ -0,0 +1,26 @@
+#ifndef INCLUDED
+#define INCLUDED
+
+#pragma OPENCL EXTENSION all : begin
+#pragma OPENCL EXTENSION all : end
+
+#pragma OPENCL EXTENSION my_ext : begin
+
+struct A {
+  int a;
+};
+
+typedef struct A TypedefOfA;
+typedef const __private TypedefOfA* PointerOfA;
+
+void f(void);
+
+__attribute__((overloadable)) void g(long x);
+
+#pragma OPENCL EXTENSION my_ext : end
+#pragma OPENCL EXTENSION my_ext : end
+
+__attribute__((overloadable)) void g(void);
+
+#endif // INCLUDED
+