[lld] Write the DataCRC to the output PDB

[zturner]

Summary

This matches what MSVC does, and I have confirmed that the CRC we write is the same value as the one they write.

[rnk]

lgtm! Maybe RelocCrc is the CRC of the base relocations? Unclear.

[compnerd]

lld/COFF/PDB.cpp

696

Probably can get away with auto here.

lld/COFF/PDB.cpp

 #include "llvm/DebugInfo/PDB/Native/TpiHashing.h"
 #include "llvm/DebugInfo/PDB/Native/TpiStream.h"
 #include "llvm/DebugInfo/PDB/Native/TpiStreamBuilder.h"
 #include "llvm/DebugInfo/PDB/PDB.h"
 #include "llvm/Object/COFF.h"
 #include "llvm/Support/BinaryByteStream.h"
 #include "llvm/Support/Endian.h"
 #include "llvm/Support/FileOutputBuffer.h"
+#include "llvm/Support/JamCRC.h"
 #include "llvm/Support/Path.h"
 #include "llvm/Support/ScopedPrinter.h"
 #include <memory>
 
 using namespace lld;
 using namespace lld::coff;
 using namespace llvm;
 using namespace llvm::codeview;
void PDBLinker::addSectionContrib(pdb::DbiModuleDescriptorBuilder &LinkerModule,
   pdb::SectionContrib SC;
   memset(&SC, 0, sizeof(SC));
   SC.ISect = OS->SectionIndex;
   SC.Off = C->getRVA() - OS->getRVA();
   SC.Size = C->getSize();
   if (auto *SecChunk = dyn_cast<SectionChunk>(C)) {
     SC.Characteristics = SecChunk->Header->Characteristics;
     SC.Imod = SecChunk->File->ModuleDBI->getModuleIndex();
+    ArrayRef<uint8_t> Contents = SecChunk->getContents();
+    JamCRC CRC(0);
+    ArrayRef<char> CharContents = makeArrayRef(
+        reinterpret_cast<const char *>(Contents.data()), Contents.size());
+    CRC.update(CharContents);
+    SC.DataCrc = CRC.getCRC();
   } else {
     SC.Characteristics = OS->getCharacteristics();
     // FIXME: When we start creating DBI for import libraries, use those here.
     SC.Imod = LinkerModule.getModuleIndex();
   }
-  SC.DataCrc = 0;  // FIXME
   SC.RelocCrc = 0; // FIXME
   Builder.getDbiBuilder().addSectionContrib(SC);
 }
 
 void PDBLinker::addSections(ArrayRef<OutputSection *> OutputSections,
                             ArrayRef<uint8_t> SectionTable) {
   // It's not entirely clear what this is, but the * Linker * module uses it.
   pdb::DbiStreamBuilder &DbiBuilder = Builder.getDbiBuilder();

lld/test/COFF/pdb.test

 RAW-NEXT:   40000040 flags
 RAW-NEXT:            IMAGE_SCN_CNT_INITIALIZED_DATA
 RAW-NEXT:            IMAGE_SCN_MEM_READ
 RAW:                        Original Section Headers
 RAW-NEXT: ============================================================
 RAW-NEXT:   PDB does not contain the requested image section header type
 RAW:                        Section Contributions
 RAW-NEXT: ============================================================
-RAW-NEXT:   SC[.pdata]  | mod = 0, 0001:0000, size = 12, data crc = 0, reloc crc = 0
+RAW-NEXT:   SC[.pdata]  | mod = 0, 0001:0000, size = 12, data crc = 361370162, reloc crc = 0
 RAW-NEXT:                 IMAGE_SCN_CNT_INITIALIZED_DATA | IMAGE_SCN_ALIGN_4BYTES | IMAGE_SCN_MEM_READ
-RAW-NEXT:   SC[.text]   | mod = 0, 0002:0000, size = 14, data crc = 0, reloc crc = 0
+RAW-NEXT:   SC[.text]   | mod = 0, 0002:0000, size = 14, data crc = 1682752513, reloc crc = 0
 RAW-NEXT:                 IMAGE_SCN_CNT_CODE | IMAGE_SCN_ALIGN_16BYTES | IMAGE_SCN_MEM_EXECUTE |
 RAW-NEXT:                 IMAGE_SCN_MEM_READ
-RAW-NEXT:   SC[.text]   | mod = 1, 0002:0016, size = 6, data crc = 0, reloc crc = 0
+RAW-NEXT:   SC[.text]   | mod = 1, 0002:0016, size = 6, data crc = 2139436471, reloc crc = 0
 RAW-NEXT:                 IMAGE_SCN_CNT_CODE | IMAGE_SCN_ALIGN_16BYTES | IMAGE_SCN_MEM_EXECUTE |
 RAW-NEXT:                 IMAGE_SCN_MEM_READ
-RAW-NEXT:   SC[.xdata]  | mod = 0, 0003:0000, size = 8, data crc = 0, reloc crc = 0
+RAW-NEXT:   SC[.xdata]  | mod = 0, 0003:0000, size = 8, data crc = 264583633, reloc crc = 0
 RAW-NEXT:                 IMAGE_SCN_CNT_INITIALIZED_DATA | IMAGE_SCN_ALIGN_4BYTES | IMAGE_SCN_MEM_READ
 RAW:                             Section Map
 RAW-NEXT: ============================================================
 RAW-NEXT:   Section 0000 | ovl = 0, group = 0, frame = 1, name = 65535
 RAW-NEXT:                  class = 65535, offset = 0, size =
 RAW-NEXT:                  flags = read | 32 bit addr | selector
 RAW-NEXT:   Section 0001 | ovl = 0, group = 0, frame = 2, name = 65535
 RAW-NEXT:                  class = 65535, offset = 0, size =