[Orc] Fix remaining memory size of slab allocator

Author: weliveindetail

llvm/lib/ExecutionEngine/JITLink/JITLinkMemoryManager.cpp

@@ -116,7 +116,7 @@ InProcessMemoryManager::allocate(const JITLinkDylib *JD,
 
     sys::MemoryBlock SegMem(SlabRemaining.base(), SegmentSize);
     SlabRemaining = sys::MemoryBlock((char *)SlabRemaining.base() + SegmentSize,
-                                     SegmentSize);
+                                     SlabRemaining.allocatedSize() - SegmentSize);
 
     // Zero out the zero-fill memory.
     memset(static_cast<char *>(SegMem.base()) + Seg.getContentSize(), 0,
@@ -125,6 +125,8 @@ InProcessMemoryManager::allocate(const JITLinkDylib *JD,
     // Record the block for this segment.
     Blocks[KV.first] = std::move(SegMem);
   }
+
+  assert(SlabRemaining.allocatedSize() >= 0 && "Mapping exceeds allocation");
   return std::unique_ptr<InProcessMemoryManager::Allocation>(
       new IPMMAlloc(std::move(Blocks)));
 }