diff --git a/llvm/lib/ExecutionEngine/JITLink/JITLink.cpp b/llvm/lib/ExecutionEngine/JITLink/JITLink.cpp
--- a/llvm/lib/ExecutionEngine/JITLink/JITLink.cpp
+++ b/llvm/lib/ExecutionEngine/JITLink/JITLink.cpp
@@ -213,7 +213,12 @@
     // Transfer all symbols with offset less than SplitIndex to NewBlock.
     while (!BlockSymbols.empty() &&
            BlockSymbols.back()->getOffset() < SplitIndex) {
-      BlockSymbols.back()->setBlock(NewBlock);
+      auto *Sym = BlockSymbols.back();
+      // If the symbol extends beyond the split, update the size to be within
+      // the new block.
+      if (Sym->getOffset() + Sym->getSize() > SplitIndex)
+        Sym->setSize(SplitIndex - Sym->getOffset());
+      Sym->setBlock(NewBlock);
       BlockSymbols.pop_back();
     }
 
diff --git a/llvm/unittests/ExecutionEngine/JITLink/LinkGraphTests.cpp b/llvm/unittests/ExecutionEngine/JITLink/LinkGraphTests.cpp
--- a/llvm/unittests/ExecutionEngine/JITLink/LinkGraphTests.cpp
+++ b/llvm/unittests/ExecutionEngine/JITLink/LinkGraphTests.cpp
@@ -493,6 +493,9 @@
                                 false, false);
   auto &S4 = G.addDefinedSymbol(B1, 12, "S4", 4, Linkage::Strong,
                                 Scope::Default, false, false);
+  // Add a symbol that extends beyond the split.
+  auto &S5 = G.addDefinedSymbol(B1, 0, "S5", 16, Linkage::Strong,
+                                Scope::Default, false, false);
 
   // Add an extra block, EB, and target symbols, and use these to add edges
   // from B1 to EB.
@@ -538,6 +541,11 @@
   EXPECT_EQ(&S4.getBlock(), &B1);
   EXPECT_EQ(S4.getOffset(), 4U);
 
+  EXPECT_EQ(&S5.getBlock(), &B2);
+  EXPECT_EQ(S5.getOffset(), 0U);
+  // Size shrinks to fit.
+  EXPECT_EQ(S5.getSize(), 8U);
+
   // Check that edges in B1 have been transferred as expected:
   // Both blocks should now have two edges each at offsets 0 and 4.
   EXPECT_EQ(llvm::size(B1.edges()), 2);