Merge pull request #21956 from akyrtzi/5.0-import-loc-pch

[5.0][ClangImporter] Fix issue with source order comparisons of clang source locations when using a bridging PCH

Author: akyrtzi

lib/ClangImporter/ClangImporter.cpp

@@ -1144,6 +1144,14 @@ ClangImporter::Implementation::getNextIncludeLoc() {
   if (!DummyIncludeBuffer.isValid()) {
     clang::SourceLocation includeLoc =
         srcMgr.getLocForStartOfFile(srcMgr.getMainFileID());
+    // Picking the beginning of the main FileID as include location is also what
+    // the clang PCH mechanism is doing (see
+    // clang::ASTReader::getImportLocation()). Choose the next source location
+    // here to avoid having the exact same import location as the clang PCH.
+    // Otherwise, if we are using a PCH for bridging header, we'll have
+    // problems with source order comparisons of clang source locations not
+    // being deterministic.
+    includeLoc = includeLoc.getLocWithOffset(1);
     DummyIncludeBuffer = srcMgr.createFileID(
         llvm::make_unique<ZeroFilledMemoryBuffer>(
           256*1024, StringRef(moduleImportBufferName)),

test/IDE/clang-importing/Inputs/bridge.h

@@ -1 +1,4 @@
+@import Foundation;
 @import somemod1;
+
+void func_in_bridge(void);

test/IDE/clang-importing/complete_with_clang_comments.swift

@@ -1,5 +1,7 @@
-// RUN: %target-swift-ide-test -code-completion -source-filename %s -code-completion-token=TOP -code-completion-comments=true \
+// RUN: %target-swift-ide-test(mock-sdk: %clang-importer-sdk) -code-completion -source-filename %s -code-completion-token=TOP -code-completion-comments=true \
 // RUN:    -import-objc-header %S/Inputs/bridge.h -I %S/Inputs/somemod1 -I %S/Inputs/somemod2 | %FileCheck %s -check-prefix=CHECK-TOP
+// RUN: %target-swift-ide-test(mock-sdk: %clang-importer-sdk) -code-completion -source-filename %s -code-completion-token=TOP -code-completion-comments=true \
+// RUN:    -import-objc-header %S/Inputs/bridge.h -pch-output-dir %t.pch -I %S/Inputs/somemod1 -I %S/Inputs/somemod2 | %FileCheck %s -check-prefix=CHECK-TOP
 
 // REQUIRES: objc_interop