Revert "Reapply "[DebugInfo] Alternate (more efficient) MD5 fix""

This reverts commit 2e4d2d8.

Invalid checksums detected here:
https://lab.llvm.org/buildbot/#/builders/37/builds/24465

Author: pogo59

clang/lib/CodeGen/CGDebugInfo.cpp

@@ -391,14 +391,12 @@ llvm::DIFile *CGDebugInfo::getOrCreateFile(SourceLocation Loc) {
   SourceManager &SM = CGM.getContext().getSourceManager();
   StringRef FileName;
   FileID FID;
-  std::optional<llvm::DIFile::ChecksumInfo<StringRef>> CSInfo;
 
   if (Loc.isInvalid()) {
     // The DIFile used by the CU is distinct from the main source file. Call
     // createFile() below for canonicalization if the source file was specified
     // with an absolute path.
     FileName = TheCU->getFile()->getFilename();
-    CSInfo = TheCU->getFile()->getChecksum();
   } else {
     PresumedLoc PLoc = SM.getPresumedLoc(Loc);
     FileName = PLoc.getFilename();
@@ -419,13 +417,13 @@ llvm::DIFile *CGDebugInfo::getOrCreateFile(SourceLocation Loc) {
       return cast<llvm::DIFile>(V);
   }
 
-  if (!CSInfo) {
-    SmallString<64> Checksum;
-    std::optional<llvm::DIFile::ChecksumKind> CSKind =
+  SmallString<64> Checksum;
+
+  std::optional<llvm::DIFile::ChecksumKind> CSKind =
       computeChecksum(FID, Checksum);
-    if (CSKind)
-      CSInfo.emplace(*CSKind, Checksum);
-  }
+  std::optional<llvm::DIFile::ChecksumInfo<StringRef>> CSInfo;
+  if (CSKind)
+    CSInfo.emplace(*CSKind, Checksum);
   return createFile(FileName, CSInfo, getSource(SM, SM.getFileID(Loc)));
 }
 

clang/lib/CodeGen/CGDebugInfo.h

@@ -148,7 +148,7 @@ class CGDebugInfo {
   llvm::BumpPtrAllocator DebugInfoNames;
   StringRef CWDName;
 
-  llvm::DenseMap<const char *, llvm::TrackingMDRef> DIFileCache;
+  llvm::StringMap<llvm::TrackingMDRef> DIFileCache;
   llvm::DenseMap<const FunctionDecl *, llvm::TrackingMDRef> SPCache;
   /// Cache declarations relevant to DW_TAG_imported_declarations (C++
   /// using declarations and global alias variables) that aren't covered

clang/test/CodeGenCXX/debug-info-function-context.cpp

@@ -1,5 +1,5 @@
 // RUN: %clang_cc1 -emit-llvm -debug-info-kind=limited -triple x86_64-pc-linux-gnu %s \
-// RUN:     -dwarf-version=5 -main-file-name debug-info-function-context.cpp  -o - | FileCheck %s
+// RUN:     -dwarf-version=5 -main-file-name %s  -o - | FileCheck %s
 
 struct C {
   void member_function();
@@ -31,8 +31,8 @@ int global_initialized_variable = C::static_member_function();
 
 // The first DIFile is for the CU, the second is what everything else uses.
 // We're using DWARF v5 so both should have MD5 checksums.
-// CHECK: !DIFile(filename: "{{.*}}context.cpp",{{.*}} checksumkind: CSK_MD5, checksum: [[CKSUM:".*"]]
-// CHECK: ![[FILE:[0-9]+]] = !DIFile(filename: "{{.*}}context.cpp",{{.*}} checksumkind: CSK_MD5, checksum: [[CKSUM]]
+// CHECK: !DIFile(filename: "{{.*}}context.cpp",{{.*}} checksumkind: CSK_MD5
+// CHECK: ![[FILE:[0-9]+]] = !DIFile(filename: "{{.*}}context.cpp",{{.*}} checksumkind: CSK_MD5
 // CHECK: ![[C:[0-9]+]] = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "C",
 // CHECK: ![[NS:.*]] = !DINamespace(name: "ns"
 // CHECK: !DISubprogram(name: "member_function",{{.*}} scope: ![[C]],{{.*}} DISPFlagDefinition