[Preamble] Reuse preamble even if an unsaved file does not exist

When a preamble is created an unsaved file not existing on disk is
already part of PrecompiledPreamble::FilesInPreamble. However, when
checking whether the preamble can be re-used, a failed stat of such an
unsaved file invalidated the preamble, which led to pointless and time
consuming preamble regenerations on subsequent reparses.

Do not require anymore that unsaved files should exist on disk.

This avoids costly preamble invalidations depending on timing issues for
the cases where the file on disk might be removed just to be regenerated
a bit later.

It also allows an IDE to provide in-memory files that might not exist on
disk, e.g. because the build system hasn't generated those yet.

Differential Revision: https://reviews.llvm.org/D41005


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@361226 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 70 insertions, 4 deletions

diff --git a/unittests/Frontend/PCHPreambleTest.cpp b/unittests/Frontend/PCHPreambleTest.cpp
index 70567405f1..0dc567efaa 100644
--- a/unittests/Frontend/PCHPreambleTest.cpp
+++ b/unittests/Frontend/PCHPreambleTest.cpp
@@ -52,7 +52,10 @@ class PCHPreambleTest : public ::testing::Test {
   FileSystemOptions FSOpts;
 
 public:
-  void SetUp() override {
+  void SetUp() override { ResetVFS(); }
+  void TearDown() override {}
+
+  void ResetVFS() {
     VFS = new ReadCountingInMemoryFileSystem();
     // We need the working directory to be set to something absolute,
     // otherwise it ends up being inadvertently set to the current
@@ -63,9 +66,6 @@ public:
     VFS->setCurrentWorkingDirectory("//./");
   }
 
-  void TearDown() override {
-  }
-
   void AddFile(const std::string &Filename, const std::string &Contents) {
     ::time_t now;
     ::time(&now);
@@ -123,6 +123,72 @@ private:
   }
 };
 
+TEST_F(PCHPreambleTest, ReparseReusesPreambleWithUnsavedFileNotExistingOnDisk) {
+  std::string Header1 = "//./header1.h";
+  std::string MainName = "//./main.cpp";
+  AddFile(MainName, R"cpp(
+#include "//./header1.h"
+int main() { return ZERO; }
+)cpp");
+  RemapFile(Header1, "#define ZERO 0\n");
+
+  // Parse with header file provided as unsaved file, which does not exist on
+  // disk.
+  std::unique_ptr<ASTUnit> AST(ParseAST(MainName));
+  ASSERT_TRUE(AST.get());
+  ASSERT_FALSE(AST->getDiagnostics().hasErrorOccurred());
+
+  // Reparse and check that the preamble was reused.
+  ASSERT_TRUE(ReparseAST(AST));
+  ASSERT_EQ(AST->getPreambleCounterForTests(), 1U);
+}
+
+TEST_F(PCHPreambleTest, ReparseReusesPreambleAfterUnsavedFileWasCreatedOnDisk) {
+  std::string Header1 = "//./header1.h";
+  std::string MainName = "//./main.cpp";
+  AddFile(MainName, R"cpp(
+#include "//./header1.h"
+int main() { return ZERO; }
+)cpp");
+  RemapFile(Header1, "#define ZERO 0\n");
+
+  // Parse with header file provided as unsaved file, which does not exist on
+  // disk.
+  std::unique_ptr<ASTUnit> AST(ParseAST(MainName));
+  ASSERT_TRUE(AST.get());
+  ASSERT_FALSE(AST->getDiagnostics().hasErrorOccurred());
+
+  // Create the unsaved file also on disk and check that preamble was reused.
+  AddFile(Header1, "#define ZERO 0\n");
+  ASSERT_TRUE(ReparseAST(AST));
+  ASSERT_EQ(AST->getPreambleCounterForTests(), 1U);
+}
+
+TEST_F(PCHPreambleTest,
+       ReparseReusesPreambleAfterUnsavedFileWasRemovedFromDisk) {
+  std::string Header1 = "//./foo/header1.h";
+  std::string MainName = "//./main.cpp";
+  std::string MainFileContent = R"cpp(
+#include "//./foo/header1.h"
+int main() { return ZERO; }
+)cpp";
+  AddFile(MainName, MainFileContent);
+  AddFile(Header1, "#define ZERO 0\n");
+  RemapFile(Header1, "#define ZERO 0\n");
+
+  // Parse with header file provided as unsaved file, which exists on disk.
+  std::unique_ptr<ASTUnit> AST(ParseAST(MainName));
+  ASSERT_TRUE(AST.get());
+  ASSERT_FALSE(AST->getDiagnostics().hasErrorOccurred());
+  ASSERT_EQ(AST->getPreambleCounterForTests(), 1U);
+
+  // Remove the unsaved file from disk and check that the preamble was reused.
+  ResetVFS();
+  AddFile(MainName, MainFileContent);
+  ASSERT_TRUE(ReparseAST(AST));
+  ASSERT_EQ(AST->getPreambleCounterForTests(), 1U);
+}
+
 TEST_F(PCHPreambleTest, ReparseWithOverriddenFileDoesNotInvalidatePreamble) {
   std::string Header1 = "//./header1.h";
   std::string Header2 = "//./header2.h";