[pdb/lld] Write a valid FPM.

The PDB reserves certain blocks for the FPM that describe which
blocks in the file are allocated and which are free.  We weren't
filling that out at all, and in some cases we were even stomping
it with incorrect data.  This patch writes a correct FPM.

Differential Revision: https://reviews.llvm.org/D36235

llvm-svn: 309896

1 files changed, 28 insertions, 0 deletions

diff --git a/llvm/lib/DebugInfo/PDB/Native/PDBFileBuilder.cpp b/llvm/lib/DebugInfo/PDB/Native/PDBFileBuilder.cpp
index a8b80ac..09e86bf 100644
--- a/llvm/lib/DebugInfo/PDB/Native/PDBFileBuilder.cpp
+++ b/llvm/lib/DebugInfo/PDB/Native/PDBFileBuilder.cpp
@@ -155,6 +155,31 @@ Expected<uint32_t> PDBFileBuilder::getNamedStreamIndex(StringRef Name) const {
   return SN;
 }
 
+void PDBFileBuilder::commitFpm(WritableBinaryStream &MsfBuffer,
+                               const MSFLayout &Layout) {
+  auto FpmStream =
+      WritableMappedBlockStream::createFpmStream(Layout, MsfBuffer, Allocator);
+
+  // We only need to create the alt fpm stream so that it gets initialized.
+  WritableMappedBlockStream::createFpmStream(Layout, MsfBuffer, Allocator,
+                                             true);
+
+  uint32_t BI = 0;
+  BinaryStreamWriter FpmWriter(*FpmStream);
+  while (BI < Layout.SB->NumBlocks) {
+    uint8_t ThisByte = 0;
+    for (uint32_t I = 0; I < 8; ++I) {
+      bool IsFree =
+          (BI < Layout.SB->NumBlocks) ? Layout.FreePageMap.test(BI) : true;
+      uint8_t Mask = uint8_t(IsFree) << I;
+      ThisByte |= Mask;
+      ++BI;
+    }
+    cantFail(FpmWriter.writeObject(ThisByte));
+  }
+  assert(FpmWriter.bytesRemaining() == 0);
+}
+
 Error PDBFileBuilder::commit(StringRef Filename) {
   assert(!Filename.empty());
   auto ExpectedLayout = finalizeMsfLayout();
@@ -173,6 +198,9 @@ Error PDBFileBuilder::commit(StringRef Filename) {
 
   if (auto EC = Writer.writeObject(*Layout.SB))
     return EC;
+
+  commitFpm(Buffer, Layout);
+
   uint32_t BlockMapOffset =
       msf::blockToOffset(Layout.SB->BlockMapAddr, Layout.SB->BlockSize);
   Writer.setOffset(BlockMapOffset);