1 files changed, 6 insertions, 32 deletions

diff --git a/llvm/lib/DebugInfo/MSF/MSFBuilder.cpp b/llvm/lib/DebugInfo/MSF/MSFBuilder.cpp
index 9cd22ab7d88..919f870b34a 100644
--- a/llvm/lib/DebugInfo/MSF/MSFBuilder.cpp
+++ b/llvm/lib/DebugInfo/MSF/MSFBuilder.cpp
@@ -29,7 +29,7 @@ static const uint32_t kFreePageMap0Block = 1;
 static const uint32_t kFreePageMap1Block = 2;
 static const uint32_t kNumReservedPages = 3;
 
-static const uint32_t kDefaultFreePageMap = kFreePageMap0Block;
+static const uint32_t kDefaultFreePageMap = kFreePageMap1Block;
 static const uint32_t kDefaultBlockMapAddr = kNumReservedPages;
 
 MSFBuilder::MSFBuilder(uint32_t BlockSize, uint32_t MinBlockCount, bool CanGrow,
@@ -112,11 +112,11 @@ Error MSFBuilder::allocateBlocks(uint32_t NumBlocks,
     FreeBlocks.resize(NewBlockCount, true);
     // If we crossed over an fpm page, we actually need to allocate 2 extra
     // blocks for each FPM group crossed and mark both blocks from the group as
-    // used.  We may not actually use them since there are many more FPM blocks
-    // present than are required to represent all blocks in a given PDB, but we
-    // need to make sure they aren't allocated to a stream or something else.
-    // At the end when committing the PDB, we'll go through and mark the
-    // extraneous ones unused.
+    // used.  FPM blocks are marked as allocated regardless of whether or not
+    // they ultimately describe the status of blocks in the file.  This means
+    // that not only are extraneous blocks at the end of the main FPM marked as
+    // allocated, but also blocks from the alternate FPM are always marked as
+    // allocated.
     while (NextFpmBlock < NewBlockCount) {
       NewBlockCount += 2;
       FreeBlocks.resize(NewBlockCount, true);
@@ -244,19 +244,6 @@ uint32_t MSFBuilder::computeDirectoryByteSize() const {
   return Size;
 }
 
-static void finalizeFpmBlockStatus(uint32_t B, ArrayRef<ulittle32_t> &FpmBlocks,
-                                   BitVector &Fpm) {
-  if (FpmBlocks.empty() || FpmBlocks.front() != B) {
-    Fpm.set(B);
-    return;
-  }
-
-  // If the next block in the actual layout is this block, it should *not* be
-  // free.
-  assert(!Fpm.test(B));
-  FpmBlocks = FpmBlocks.drop_front();
-}
-
 Expected<MSFLayout> MSFBuilder::build() {
   SuperBlock *SB = Allocator.Allocate<SuperBlock>();
   MSFLayout L;
@@ -315,19 +302,6 @@ Expected<MSFLayout> MSFBuilder::build() {
     }
   }
 
-  // FPM blocks occur in pairs at every `BlockLength` interval.  While blocks of
-  // this form are reserved for FPM blocks, not all blocks of this form will
-  // actually be needed for FPM data because there are more blocks of this form
-  // than are required to represent a PDB file with a given number of blocks.
-  // So we need to find out which blocks are *actually* going to be real FPM
-  // blocks, then mark the reset of the reserved blocks as unallocated.
-  MSFStreamLayout FpmLayout = msf::getFpmStreamLayout(L, true);
-  auto FpmBlocks = makeArrayRef(FpmLayout.Blocks);
-  for (uint32_t B = kFreePageMap0Block; B < SB->NumBlocks;
-       B += msf::getFpmIntervalLength(L)) {
-    finalizeFpmBlockStatus(B, FpmBlocks, FreeBlocks);
-    finalizeFpmBlockStatus(B + 1, FpmBlocks, FreeBlocks);
-  }
   L.FreePageMap = FreeBlocks;
 
   return L;