[pdb] Use MsfBuilder to handle the writing PDBs.

Previously we would read a PDB, then write some of it back out,
but write the directory, super block, and other pertinent metadata
back out unchanged.  This generates incorrect PDBs since the amount
of data written was not always the same as the amount of data read.

This patch changes things to use the newly introduced `MsfBuilder`
class to write out a correct and accurate set of Msf metadata for
the data *actually* written, which opens up the door for adding and
removing type records, symbol records, and other types of data to
an existing PDB.

llvm-svn: 275627

1 files changed, 39 insertions, 8 deletions

diff --git a/llvm/lib/DebugInfo/PDB/Raw/MsfBuilder.cpp b/llvm/lib/DebugInfo/PDB/Raw/MsfBuilder.cpp
index ab739d339a9..fecefbfeb8d 100644
--- a/llvm/lib/DebugInfo/PDB/Raw/MsfBuilder.cpp
+++ b/llvm/lib/DebugInfo/PDB/Raw/MsfBuilder.cpp
@@ -24,7 +24,7 @@ MsfBuilder::MsfBuilder(uint32_t BlockSize, uint32_t MinBlockCount, bool CanGrow,
                        BumpPtrAllocator &Allocator)
     : Allocator(Allocator), IsGrowable(CanGrow), BlockSize(BlockSize),
       MininumBlocks(MinBlockCount), BlockMapAddr(kDefaultBlockMapAddr),
-      FreeBlocks(MinBlockCount + 2U, true) {
+      FreeBlocks(std::max(MinBlockCount, 2U), true) {
   FreeBlocks[kSuperBlockBlock] = false;
   FreeBlocks[BlockMapAddr] = false;
 }
@@ -59,6 +59,25 @@ Error MsfBuilder::setBlockMapAddr(uint32_t Addr) {
   return Error::success();
 }
 
+void MsfBuilder::setUnknown0(uint32_t Unk0) { Unknown0 = Unk0; }
+
+void MsfBuilder::setUnknown1(uint32_t Unk1) { Unknown1 = Unk1; }
+
+Error MsfBuilder::setDirectoryBlocksHint(ArrayRef<uint32_t> DirBlocks) {
+  for (auto B : DirectoryBlocks)
+    FreeBlocks[B] = true;
+  for (auto B : DirBlocks) {
+    if (!isBlockFree(B)) {
+      return make_error<RawError>(raw_error_code::unspecified,
+                                  "Attempt to reuse an allocated block");
+    }
+    FreeBlocks[B] = false;
+  }
+
+  DirectoryBlocks = DirBlocks;
+  return Error::success();
+}
+
 Error MsfBuilder::allocateBlocks(uint32_t NumBlocks,
                                  MutableArrayRef<uint32_t> Blocks) {
   if (NumBlocks == 0)
@@ -198,16 +217,28 @@ Expected<Layout> MsfBuilder::build() {
   L.SB->BlockMapAddr = BlockMapAddr;
   L.SB->BlockSize = BlockSize;
   L.SB->NumDirectoryBytes = computeDirectoryByteSize();
-  L.SB->Unknown0 = 0;
-  L.SB->Unknown1 = 0;
+  L.SB->Unknown0 = Unknown0;
+  L.SB->Unknown1 = Unknown1;
 
   uint32_t NumDirectoryBlocks =
       bytesToBlocks(L.SB->NumDirectoryBytes, BlockSize);
-  // The directory blocks should be re-allocated as a stable pointer.
-  std::vector<uint32_t> DirectoryBlocks;
-  DirectoryBlocks.resize(NumDirectoryBlocks);
-  if (auto EC = allocateBlocks(NumDirectoryBlocks, DirectoryBlocks))
-    return std::move(EC);
+  if (NumDirectoryBlocks > DirectoryBlocks.size()) {
+    // Our hint wasn't enough to satisfy the entire directory.  Allocate
+    // remaining pages.
+    std::vector<uint32_t> ExtraBlocks;
+    uint32_t NumExtraBlocks = NumDirectoryBlocks - DirectoryBlocks.size();
+    ExtraBlocks.resize(NumExtraBlocks);
+    if (auto EC = allocateBlocks(NumExtraBlocks, ExtraBlocks))
+      return std::move(EC);
+    DirectoryBlocks.insert(DirectoryBlocks.end(), ExtraBlocks.begin(),
+                           ExtraBlocks.end());
+  } else if (NumDirectoryBlocks < DirectoryBlocks.size()) {
+    uint32_t NumUnnecessaryBlocks = DirectoryBlocks.size() - NumDirectoryBlocks;
+    for (auto B :
+         ArrayRef<uint32_t>(DirectoryBlocks).drop_back(NumUnnecessaryBlocks))
+      FreeBlocks[B] = true;
+    DirectoryBlocks.resize(NumDirectoryBlocks);
+  }
 
   // Don't set the number of blocks in the file until after allocating Blocks
   // for