Use the DiagnosticHandler to print diagnostics when reading bitcode.

The bitcode reading interface used std::error_code to report an error to the
callers and it is the callers job to print diagnostics.

This is not ideal for error handling or diagnostic reporting:

* For error handling, all that the callers care about is 3 possibilities:
  * It worked
  * The bitcode file is corrupted/invalid.
  * The file is not bitcode at all.

* For diagnostic, it is user friendly to include far more information
  about the invalid case so the user can find out what is wrong with the
  bitcode file. This comes up, for example, when a developer introduces a
  bug while extending the format.

The compromise we had was to have a lot of error codes.

With this patch we use the DiagnosticHandler to communicate with the
human and std::error_code to communicate with the caller.

This allows us to have far fewer error codes and adds the infrastructure to
print better diagnostics. This is so because the diagnostics are printed when
he issue is found. The code that detected the problem in alive in the stack and
can pass down as much context as needed. As an example the patch updates
test/Bitcode/invalid.ll.

Using a DiagnosticHandler also moves the fatal/non-fatal error decision to the
caller. A simple one like llvm-dis can just use fatal errors. The gold plugin
needs a bit more complex treatment because of being passed non-bitcode files. An
hypothetical interactive tool would make all bitcode errors non-fatal.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@225562 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Bitcode/ReaderWriter.h

@@ -14,6 +14,7 @@
 #ifndef LLVM_BITCODE_READERWRITER_H
 #define LLVM_BITCODE_READERWRITER_H
 
+#include "llvm/IR/DiagnosticInfo.h"
 #include "llvm/Support/ErrorOr.h"
 #include "llvm/Support/MemoryBuffer.h"
 #include <memory>
@@ -30,24 +31,28 @@ namespace llvm {
   /// Read the header of the specified bitcode buffer and prepare for lazy
   /// deserialization of function bodies.  If successful, this moves Buffer. On
   /// error, this *does not* move Buffer.
-  ErrorOr<Module *> getLazyBitcodeModule(std::unique_ptr<MemoryBuffer> &&Buffer,
-                                         LLVMContext &Context);
+  ErrorOr<Module *>
+  getLazyBitcodeModule(std::unique_ptr<MemoryBuffer> &&Buffer,
+                       LLVMContext &Context,
+                       DiagnosticHandlerFunction DiagnosticHandler = nullptr);
 
   /// Read the header of the specified stream and prepare for lazy
   /// deserialization and streaming of function bodies.
-  ErrorOr<std::unique_ptr<Module>>
-  getStreamedBitcodeModule(StringRef Name, DataStreamer *Streamer,
-                           LLVMContext &Context);
+  ErrorOr<std::unique_ptr<Module>> getStreamedBitcodeModule(
+      StringRef Name, DataStreamer *Streamer, LLVMContext &Context,
+      DiagnosticHandlerFunction DiagnosticHandler = nullptr);
 
   /// Read the header of the specified bitcode buffer and extract just the
   /// triple information. If successful, this returns a string. On error, this
   /// returns "".
-  std::string getBitcodeTargetTriple(MemoryBufferRef Buffer,
-                                     LLVMContext &Context);
+  std::string
+  getBitcodeTargetTriple(MemoryBufferRef Buffer, LLVMContext &Context,
+                         DiagnosticHandlerFunction DiagnosticHandler = nullptr);
 
   /// Read the specified bitcode file, returning the module.
-  ErrorOr<Module *> parseBitcodeFile(MemoryBufferRef Buffer,
-                                     LLVMContext &Context);
+  ErrorOr<Module *>
+  parseBitcodeFile(MemoryBufferRef Buffer, LLVMContext &Context,
+                   DiagnosticHandlerFunction DiagnosticHandler = nullptr);
 
   /// WriteBitcodeToFile - Write the specified module to the specified
   /// raw output stream.  For streams where it matters, the given stream
@@ -138,32 +143,26 @@ namespace llvm {
   }
 
   const std::error_category &BitcodeErrorCategory();
-  enum class BitcodeError {
-    ConflictingMETADATA_KINDRecords,
-    CouldNotFindFunctionInStream,
-    ExpectedConstant,
-    InsufficientFunctionProtos,
-    InvalidBitcodeSignature,
-    InvalidBitcodeWrapperHeader,
-    InvalidConstantReference,
-    InvalidID, // A read identifier is not found in the table it should be in.
-    InvalidInstructionWithNoBB,
-    InvalidRecord, // A read record doesn't have the expected size or structure
-    InvalidTypeForValue, // Type read OK, but is invalid for its use
-    InvalidTYPETable,
-    InvalidType,    // We were unable to read a type
-    MalformedBlock, // We are unable to advance in the stream.
-    MalformedGlobalInitializerSet,
-    InvalidMultipleBlocks, // We found multiple blocks of a kind that should
-                           // have only one
-    NeverResolvedValueFoundInFunction,
-    NeverResolvedFunctionFromBlockAddress,
-    InvalidValue // Invalid version, inst number, attr number, etc
-  };
+  enum class BitcodeError { InvalidBitcodeSignature, CorruptedBitcode };
   inline std::error_code make_error_code(BitcodeError E) {
     return std::error_code(static_cast<int>(E), BitcodeErrorCategory());
   }
 
+  class BitcodeDiagnosticInfo : public DiagnosticInfo {
+    const Twine &Msg;
+    std::error_code EC;
+
+  public:
+    BitcodeDiagnosticInfo(std::error_code EC, DiagnosticSeverity Severity,
+                          const Twine &Msg);
+    void print(DiagnosticPrinter &DP) const override;
+    std::error_code getError() const { return EC; };
+
+    static bool classof(const DiagnosticInfo *DI) {
+      return DI->getKind() == DK_Bitcode;
+    }
+  };
+
 } // End llvm namespace
 
 namespace std {