diff --git a/llvm/lib/ExecutionEngine/JITLink/COFFLinkGraphBuilder.h b/llvm/lib/ExecutionEngine/JITLink/COFFLinkGraphBuilder.h
--- a/llvm/lib/ExecutionEngine/JITLink/COFFLinkGraphBuilder.h
+++ b/llvm/lib/ExecutionEngine/JITLink/COFFLinkGraphBuilder.h
@@ -114,6 +114,7 @@
   struct ComdatExportRequest {
     COFFSymbolIndex SymbolIndex;
     jitlink::Linkage Linkage;
+    orc::ExecutorAddrDiff Size;
   };
   std::vector<Optional<ComdatExportRequest>> PendingComdatExports;
 
diff --git a/llvm/lib/ExecutionEngine/JITLink/COFFLinkGraphBuilder.cpp b/llvm/lib/ExecutionEngine/JITLink/COFFLinkGraphBuilder.cpp
--- a/llvm/lib/ExecutionEngine/JITLink/COFFLinkGraphBuilder.cpp
+++ b/llvm/lib/ExecutionEngine/JITLink/COFFLinkGraphBuilder.cpp
@@ -579,7 +579,8 @@
       dbgs() << "    " << SymIndex
              << ": Partially supported IMAGE_COMDAT_SELECT_LARGEST was used"
                 " in section "
-             << Symbol.getSectionNumber() << "\n";
+             << Symbol.getSectionNumber() << " (size: " << Definition->Length
+             << ")\n";
     });
     L = Linkage::Weak;
     break;
@@ -594,9 +595,9 @@
                                     formatv("{0:d}", Definition->Selection));
   }
   }
-  PendingComdatExports[Symbol.getSectionNumber()] = {SymIndex, L};
-  return &G->addAnonymousSymbol(*B, Symbol.getValue(), Definition->Length,
-                                false, false);
+  PendingComdatExports[Symbol.getSectionNumber()] = {SymIndex, L,
+                                                     Definition->Length};
+  return nullptr;
 }
 
 // Process the second symbol of COMDAT sequence.
@@ -604,31 +605,27 @@
 COFFLinkGraphBuilder::exportCOMDATSymbol(COFFSymbolIndex SymIndex,
                                          StringRef SymbolName,
                                          object::COFFSymbolRef Symbol) {
+  Block *B = getGraphBlock(Symbol.getSectionNumber());
   auto &PendingComdatExport = PendingComdatExports[Symbol.getSectionNumber()];
-  COFFSymbolIndex TargetIndex = PendingComdatExport->SymbolIndex;
-  Linkage L = PendingComdatExport->Linkage;
-  jitlink::Symbol *Target = getGraphSymbol(TargetIndex);
-  assert(Target && "COMDAT leaader is invalid.");
-  assert((llvm::count_if(G->defined_symbols(),
-                         [&](const jitlink::Symbol *Sym) {
-                           return Sym->getName() == SymbolName;
-                         }) == 0) &&
-         "Duplicate defined symbol");
-  Target->setName(SymbolName);
-  Target->setLinkage(L);
-  Target->setCallable(Symbol.getComplexType() ==
-                      COFF::IMAGE_SYM_DTYPE_FUNCTION);
-  Target->setScope(Scope::Default);
+  // NOTE: ComdatDef->Legnth is the size of "section" not size of symbol.
+  // We use zero symbol size to not reach out of bound of block when symbol
+  // offset is non-zero.
+  auto GSym = &G->addDefinedSymbol(
+      *B, Symbol.getValue(), SymbolName, 0, PendingComdatExport->Linkage,
+      Scope::Default, Symbol.getComplexType() == COFF::IMAGE_SYM_DTYPE_FUNCTION,
+      false);
   LLVM_DEBUG({
     dbgs() << "    " << SymIndex
            << ": Exporting COMDAT graph symbol for COFF symbol \"" << SymbolName
            << "\" in section " << Symbol.getSectionNumber() << "\n";
-    dbgs() << "      " << *Target << "\n";
+    dbgs() << "      " << *GSym << "\n";
   });
+  setGraphSymbol(Symbol.getSectionNumber(), PendingComdatExport->SymbolIndex,
+                 *GSym);
+  DefinedSymbols[SymbolName] = GSym;
   PendingComdatExport = None;
-  DefinedSymbols[SymbolName] = Target;
-  return Target;
+  return GSym;
 }
 
 } // namespace jitlink
 } // namespace llvm
\ No newline at end of file
diff --git a/llvm/test/ExecutionEngine/JITLink/X86/COFF_comdat_any.test b/llvm/test/ExecutionEngine/JITLink/X86/COFF_comdat_any.test
--- a/llvm/test/ExecutionEngine/JITLink/X86/COFF_comdat_any.test
+++ b/llvm/test/ExecutionEngine/JITLink/X86/COFF_comdat_any.test
@@ -5,10 +5,8 @@
 # Check a weak symbol is created for a COMDAT symbol with IMAGE_COMDAT_SELECT_ANY selection type.
 #
 # CHECK: Creating graph symbols...
-# CHECK:      2: Creating defined graph symbol for COFF symbol ".text" in .text (index: 2)
-# CHECK-NEXT:   0x0 (block + 0x00000000): size: 0x00000001, linkage: strong, scope: local, dead  -   <anonymous symbol>
-# CHECK-NEXT: 4: Exporting COMDAT graph symbol for COFF symbol "func" in section 2
-# CHECK-NEXT:   0x0 (block + 0x00000000): size: 0x00000001, linkage: weak, scope: default, dead  -   func
+# CHECK: 4: Exporting COMDAT graph symbol for COFF symbol "func" in section 2
+# CHECK-NEXT:   0x0 (block + 0x00000000): size: 0x00000000, linkage: weak, scope: default, dead  -   func
 
 --- !COFF
 header:
diff --git a/llvm/test/ExecutionEngine/JITLink/X86/COFF_comdat_exact_match.test b/llvm/test/ExecutionEngine/JITLink/X86/COFF_comdat_exact_match.test
--- a/llvm/test/ExecutionEngine/JITLink/X86/COFF_comdat_exact_match.test
+++ b/llvm/test/ExecutionEngine/JITLink/X86/COFF_comdat_exact_match.test
@@ -6,10 +6,8 @@
 # Doesn't check the content validation.
 #
 # CHECK: Creating graph symbols...
-# CHECK:      2: Creating defined graph symbol for COFF symbol ".text" in .text (index: 2)
-# CHECK-NEXT:   0x0 (block + 0x00000000): size: 0x00000001, linkage: strong, scope: local, dead  -   <anonymous symbol>
-# CHECK-NEXT: 4: Exporting COMDAT graph symbol for COFF symbol "func" in section 2
-# CHECK-NEXT:   0x0 (block + 0x00000000): size: 0x00000001, linkage: weak, scope: default, dead  -   func
+# CHECK: 4: Exporting COMDAT graph symbol for COFF symbol "func" in section 2
+# CHECK-NEXT:   0x0 (block + 0x00000000): size: 0x00000000, linkage: weak, scope: default, dead  -   func
 
 --- !COFF
 header:
diff --git a/llvm/test/ExecutionEngine/JITLink/X86/COFF_comdat_intervene.test b/llvm/test/ExecutionEngine/JITLink/X86/COFF_comdat_intervene.test
--- a/llvm/test/ExecutionEngine/JITLink/X86/COFF_comdat_intervene.test
+++ b/llvm/test/ExecutionEngine/JITLink/X86/COFF_comdat_intervene.test
@@ -6,9 +6,9 @@
 #
 # CHECK: Creating graph symbols...
 # CHECK:      6: Exporting COMDAT graph symbol for COFF symbol "func2" in section 3
-# CHECK-NEXT:   0x0 (block + 0x00000000): size: 0x00000001, linkage: weak, scope: default, dead  -   func2
+# CHECK-NEXT:   0x0 (block + 0x00000000): size: 0x00000000, linkage: weak, scope: default, dead  -   func2
 # CHECK:      7: Exporting COMDAT graph symbol for COFF symbol "func" in section 2
-# CHECK-NEXT:   0x0 (block + 0x00000000): size: 0x00000001, linkage: weak, scope: default, dead  -   func
+# CHECK-NEXT:   0x0 (block + 0x00000000): size: 0x00000000, linkage: weak, scope: default, dead  -   func
 
 --- !COFF
 header:
diff --git a/llvm/test/ExecutionEngine/JITLink/X86/COFF_comdat_largest.test b/llvm/test/ExecutionEngine/JITLink/X86/COFF_comdat_largest.test
--- a/llvm/test/ExecutionEngine/JITLink/X86/COFF_comdat_largest.test
+++ b/llvm/test/ExecutionEngine/JITLink/X86/COFF_comdat_largest.test
@@ -5,10 +5,8 @@
 # Check jitlink handles largest selection type as plain weak symbol.
 #
 # CHECK: Creating graph symbols...
-# CHECK:      2: Creating defined graph symbol for COFF symbol ".text" in .text (index: 2)
-# CHECK-NEXT:   0x0 (block + 0x00000000): size: 0x00000001, linkage: strong, scope: local, dead  -   <anonymous symbol>
-# CHECK-NEXT: 4: Exporting COMDAT graph symbol for COFF symbol "func" in section 2
-# CHECK-NEXT:   0x0 (block + 0x00000000): size: 0x00000001, linkage: weak, scope: default, dead  -   func
+# CHECK: 4: Exporting COMDAT graph symbol for COFF symbol "func" in section 2
+# CHECK-NEXT:   0x0 (block + 0x00000000): size: 0x00000000, linkage: weak, scope: default, dead  -   func
 
 --- !COFF
 header:
diff --git a/llvm/test/ExecutionEngine/JITLink/X86/COFF_comdat_noduplicate.test b/llvm/test/ExecutionEngine/JITLink/X86/COFF_comdat_noduplicate.test
--- a/llvm/test/ExecutionEngine/JITLink/X86/COFF_comdat_noduplicate.test
+++ b/llvm/test/ExecutionEngine/JITLink/X86/COFF_comdat_noduplicate.test
@@ -5,10 +5,8 @@
 # Check a strong symbol is created for a COMDAT symbol with IMAGE_COMDAT_SELECT_NODUPLICATES selection type.
 #
 # CHECK: Creating graph symbols...
-# CHECK:      2: Creating defined graph symbol for COFF symbol ".text" in .text (index: 2)
-# CHECK-NEXT:   0x0 (block + 0x00000000): size: 0x00000001, linkage: strong, scope: local, dead  -   <anonymous symbol>
-# CHECK-NEXT: 4: Exporting COMDAT graph symbol for COFF symbol "func" in section 2
-# CHECK-NEXT:   0x0 (block + 0x00000000): size: 0x00000001, linkage: strong, scope: default, dead  -   func
+# CHECK: 4: Exporting COMDAT graph symbol for COFF symbol "func" in section 2
+# CHECK-NEXT:   0x0 (block + 0x00000000): size: 0x00000000, linkage: strong, scope: default, dead  -   func
 
 --- !COFF
 header:
diff --git a/llvm/test/ExecutionEngine/JITLink/X86/COFF_comdat_any.test b/llvm/test/ExecutionEngine/JITLink/X86/COFF_comdat_offset.test
copy from llvm/test/ExecutionEngine/JITLink/X86/COFF_comdat_any.test
copy to llvm/test/ExecutionEngine/JITLink/X86/COFF_comdat_offset.test
--- a/llvm/test/ExecutionEngine/JITLink/X86/COFF_comdat_any.test
+++ b/llvm/test/ExecutionEngine/JITLink/X86/COFF_comdat_offset.test
@@ -2,13 +2,11 @@
 # RUN: yaml2obj %s -o %t
 # RUN: llvm-jitlink -noexec --debug-only=jitlink -noexec %t 2>&1 | FileCheck %s
 # 
-# Check a weak symbol is created for a COMDAT symbol with IMAGE_COMDAT_SELECT_ANY selection type.
+# Check a COMDAT symbol with an offset is handled correctly.
 #
 # CHECK: Creating graph symbols...
-# CHECK:      2: Creating defined graph symbol for COFF symbol ".text" in .text (index: 2)
-# CHECK-NEXT:   0x0 (block + 0x00000000): size: 0x00000001, linkage: strong, scope: local, dead  -   <anonymous symbol>
-# CHECK-NEXT: 4: Exporting COMDAT graph symbol for COFF symbol "func" in section 2
-# CHECK-NEXT:   0x0 (block + 0x00000000): size: 0x00000001, linkage: weak, scope: default, dead  -   func
+# CHECK: 4: Exporting COMDAT graph symbol for COFF symbol "func" in section 2
+# CHECK-NEXT:   0x1 (block + 0x00000001): size: 0x00000000, linkage: weak, scope: default, dead  -   func
 
 --- !COFF
 header:
@@ -50,7 +48,7 @@
       Number:          2
       Selection:       IMAGE_COMDAT_SELECT_ANY
   - Name:            func
-    Value:           0
+    Value:           1
     SectionNumber:   2
     SimpleType:      IMAGE_SYM_TYPE_NULL
     ComplexType:     IMAGE_SYM_DTYPE_FUNCTION
diff --git a/llvm/test/ExecutionEngine/JITLink/X86/COFF_comdat_same_size.test b/llvm/test/ExecutionEngine/JITLink/X86/COFF_comdat_same_size.test
--- a/llvm/test/ExecutionEngine/JITLink/X86/COFF_comdat_same_size.test
+++ b/llvm/test/ExecutionEngine/JITLink/X86/COFF_comdat_same_size.test
@@ -6,10 +6,8 @@
 # Doesn't check the size validation.
 #
 # CHECK: Creating graph symbols...
-# CHECK:      2: Creating defined graph symbol for COFF symbol ".text" in .text (index: 2)
-# CHECK-NEXT:   0x0 (block + 0x00000000): size: 0x00000001, linkage: strong, scope: local, dead  -   <anonymous symbol>
-# CHECK-NEXT: 4: Exporting COMDAT graph symbol for COFF symbol "func" in section 2
-# CHECK-NEXT:   0x0 (block + 0x00000000): size: 0x00000001, linkage: weak, scope: default, dead  -   func
+# CHECK: 4: Exporting COMDAT graph symbol for COFF symbol "func" in section 2
+# CHECK-NEXT:   0x0 (block + 0x00000000): size: 0x00000000, linkage: weak, scope: default, dead  -   func
 
 --- !COFF
 header:
diff --git a/llvm/test/ExecutionEngine/JITLink/X86/COFF_comdat_weak.s b/llvm/test/ExecutionEngine/JITLink/X86/COFF_comdat_weak.s
--- a/llvm/test/ExecutionEngine/JITLink/X86/COFF_comdat_weak.s
+++ b/llvm/test/ExecutionEngine/JITLink/X86/COFF_comdat_weak.s
@@ -5,10 +5,8 @@
 # Check a COMDAT any symbol is exported as a weak symbol.
 #
 # CHECK: Creating graph symbols...
-# CHECK:      6: Creating defined graph symbol for COFF symbol ".text" in .text (index: 4)
-# CHECK-NEXT:   0x0 (block + 0x00000000): size: 0x00000001, linkage: strong, scope: local, dead  -   <anonymous symbol>
-# CHECK-NEXT: 8: Exporting COMDAT graph symbol for COFF symbol "func" in section 4
-# CHECK-NEXT:   0x0 (block + 0x00000000): size: 0x00000001, linkage: weak, scope: default, dead  -   func
+# CHECK: 8: Exporting COMDAT graph symbol for COFF symbol "func" in section 4
+# CHECK-NEXT:   0x0 (block + 0x00000000): size: 0x00000000, linkage: weak, scope: default, dead  -   func
 
 	.text