Remove a lock and use a std::unique_ptr instead.

We had a lock to guard BAlloc from being used concurrently, but that
is not very easy to understand. This patch replaces it with a
std::unique_ptr.

llvm-svn: 311056

Author: rui314

lld/ELF/InputSection.cpp

@@ -200,17 +200,12 @@ void InputSectionBase::uncompress() {
                                                 Config->IsLE, Config->Is64));
 
   size_t Size = Dec.getDecompressedSize();
-  char *OutputBuf;
-  {
-    static std::mutex Mu;
-    std::lock_guard<std::mutex> Lock(Mu);
-    OutputBuf = BAlloc.Allocate<char>(Size);
-  }
-
-  if (Error E = Dec.decompress({OutputBuf, Size}))
+  UncompressBuf.reset(new std::vector<uint8_t>(Size));
+  if (Error E = Dec.decompress({(char *)UncompressBuf->data(), Size}))
     fatal(toString(this) +
           ": decompress failed: " + llvm::toString(std::move(E)));
-  this->Data = ArrayRef<uint8_t>((uint8_t *)OutputBuf, Size);
+
+  this->Data = *UncompressBuf;
   this->Flags &= ~(uint64_t)SHF_COMPRESSED;
 }
 

lld/ELF/InputSection.h

@@ -183,6 +183,11 @@ class InputSectionBase : public SectionBase {
     assert(S % sizeof(T) == 0);
     return llvm::makeArrayRef<T>((const T *)Data.data(), S / sizeof(T));
   }
+
+private:
+  // A pointer that owns uncompressed data if a section is compressed by zlib.
+  // Since the feature is not used often, this is usually a nullptr.
+  std::unique_ptr<std::vector<uint8_t>> UncompressBuf;
 };
 
 // SectionPiece represents a piece of splittable section contents.