Index: test/wasm/Inputs/comdat1.ll
===================================================================
--- /dev/null
+++ test/wasm/Inputs/comdat1.ll
@@ -0,0 +1,11 @@
+$inlineFn = comdat any
+@constantData = weak_odr constant [3 x i8] c"abc", comdat($inlineFn)
+define linkonce_odr i32 @inlineFn() comdat {
+entry:
+  ret i32 ptrtoint ([3 x i8]* @constantData to i32)
+}
+
+define i32 @callInline1() {
+entry:
+    ret i32 ptrtoint (i32 ()* @inlineFn to i32)
+}
Index: test/wasm/Inputs/comdat2.ll
===================================================================
--- /dev/null
+++ test/wasm/Inputs/comdat2.ll
@@ -0,0 +1,11 @@
+$inlineFn = comdat any
+@constantData = weak_odr constant [3 x i8] c"abc", comdat($inlineFn)
+define linkonce_odr i32 @inlineFn() comdat {
+entry:
+  ret i32 ptrtoint ([3 x i8]* @constantData to i32)
+}
+
+define i32 @callInline2() {
+entry:
+    ret i32 ptrtoint (i32 ()* @inlineFn to i32)
+}
Index: test/wasm/comdats.ll
===================================================================
--- /dev/null
+++ test/wasm/comdats.ll
@@ -0,0 +1,62 @@
+; RUN: llc -filetype=obj -mtriple=wasm32-unknown-uknown-wasm %p/Inputs/comdat1.ll -o %t1.o
+; RUN: llc -filetype=obj -mtriple=wasm32-unknown-uknown-wasm %p/Inputs/comdat2.ll -o %t2.o
+; RUN: llc -filetype=obj -mtriple=wasm32-unknown-uknown-wasm %s -o %t.o
+; RUN: lld -flavor wasm -o %t.wasm %t.o %t1.o %t2.o
+; RUN: obj2yaml %t.wasm | FileCheck %s
+
+declare i32 @inlineFn()
+
+define void @_start() local_unnamed_addr {
+entry:
+  %call = call i32 @inlineFn()
+  ret void
+}
+
+; CHECK:       - Type:            GLOBAL
+; CHECK-NEXT:    Globals:
+; CHECK-NEXT:      - Type:            I32
+; CHECK-NEXT:        Mutable:         true
+; CHECK-NEXT:        InitExpr:
+; CHECK-NEXT:          Opcode:          I32_CONST
+; CHECK-NEXT:          Value:           66576
+; CHECK-NEXT:  - Type:            EXPORT
+; CHECK-NEXT:    Exports:
+; CHECK-NEXT:      - Name:            memory
+; CHECK-NEXT:        Kind:            MEMORY
+; CHECK-NEXT:        Index:           0
+; CHECK-NEXT:      - Name:            _start
+; CHECK-NEXT:        Kind:            FUNCTION
+; CHECK-NEXT:        Index:           0
+; CHECK-NEXT:      - Name:            inlineFn
+; CHECK-NEXT:        Kind:            FUNCTION
+; CHECK-NEXT:        Index:           1
+; CHECK-NEXT:      - Name:            callInline1
+; CHECK-NEXT:        Kind:            FUNCTION
+; CHECK-NEXT:        Index:           2
+; CHECK-NEXT:      - Name:            callInline2
+; CHECK-NEXT:        Kind:            FUNCTION
+; CHECK-NEXT:        Index:           3
+; CHECK-NEXT:  - Type:            ELEM
+; CHECK-NEXT:    Segments:
+; CHECK-NEXT:      - Offset:
+; CHECK-NEXT:          Opcode:          I32_CONST
+; CHECK-NEXT:          Value:           1
+; CHECK-NEXT:        Functions:       [ 1 ]
+; CHECK-NEXT:  - Type:            CODE
+; CHECK-NEXT:    Functions:
+; CHECK-NEXT:      - Locals:
+; CHECK-NEXT:        Body:            1081808080001A0B
+; CHECK-NEXT:      - Locals:
+; CHECK-NEXT:        Body:            4180888080000B
+; CHECK-NEXT:      - Locals:
+; CHECK-NEXT:        Body:            4181808080000B
+; CHECK-NEXT:      - Locals:
+; CHECK-NEXT:        Body:            4181808080000B
+; CHECK-NEXT:  - Type:            DATA
+; CHECK-NEXT:    Segments:
+; CHECK-NEXT:      - SectionOffset:   7
+; CHECK-NEXT:        MemoryIndex:     0
+; CHECK-NEXT:        Offset:
+; CHECK-NEXT:          Opcode:          I32_CONST
+; CHECK-NEXT:          Value:           1024
+; CHECK-NEXT:        Content:         '616263'
Index: test/wasm/relocatable.ll
===================================================================
--- test/wasm/relocatable.ll
+++ test/wasm/relocatable.ll
@@ -17,6 +17,13 @@
 @func_addr2 = hidden global i32()* @foo_import, align 4
 @data_addr1 = hidden global i64* @data_import, align 8
 
+$func_comdat = comdat any
+@data_comdat = weak_odr constant [3 x i8] c"abc", comdat($func_comdat)
+define linkonce_odr i32 @func_comdat() comdat {
+entry:
+  ret i32 ptrtoint ([3 x i8]* @data_comdat to i32)
+}
+
 ; CHECK:      --- !WASM
 ; CHECK-NEXT: FileHeader:
 ; CHECK-NEXT:   Version:         0x00000001
@@ -49,7 +56,7 @@
 ; CHECK-NEXT:         GlobalType:      I32
 ; CHECK-NEXT:         GlobalMutable:   false
 ; CHECK-NEXT:   - Type:            FUNCTION
-; CHECK-NEXT:     FunctionTypes:   [ 0, 2 ]
+; CHECK-NEXT:     FunctionTypes:   [ 0, 2, 2 ]
 ; CHECK-NEXT:   - Type:            TABLE
 ; CHECK-NEXT:     Tables:
 ; CHECK-NEXT:       - ElemType:        ANYFUNC
@@ -71,6 +78,11 @@
 ; CHECK-NEXT:         Mutable:         false
 ; CHECK-NEXT:         InitExpr:
 ; CHECK-NEXT:           Opcode:          I32_CONST
+; CHECK-NEXT:           Value:           20
+; CHECK-NEXT:       - Type:            I32
+; CHECK-NEXT:         Mutable:         false
+; CHECK-NEXT:         InitExpr:
+; CHECK-NEXT:           Opcode:          I32_CONST
 ; CHECK-NEXT:           Value:           8
 ; CHECK-NEXT:       - Type:            I32
 ; CHECK-NEXT:         Mutable:         false
@@ -90,18 +102,24 @@
 ; CHECK-NEXT:       - Name:            my_func
 ; CHECK-NEXT:         Kind:            FUNCTION
 ; CHECK-NEXT:         Index:           3
+; CHECK-NEXT:       - Name:            func_comdat
+; CHECK-NEXT:         Kind:            FUNCTION
+; CHECK-NEXT:         Index:           4
 ; CHECK-NEXT:       - Name:            hello_str
 ; CHECK-NEXT:         Kind:            GLOBAL
 ; CHECK-NEXT:         Index:           1
-; CHECK-NEXT:       - Name:            func_addr1
+; CHECK-NEXT:       - Name:            data_comdat
 ; CHECK-NEXT:         Kind:            GLOBAL
 ; CHECK-NEXT:         Index:           2
-; CHECK-NEXT:       - Name:            func_addr2
+; CHECK-NEXT:       - Name:            func_addr1
 ; CHECK-NEXT:         Kind:            GLOBAL
 ; CHECK-NEXT:         Index:           3
-; CHECK-NEXT:       - Name:            data_addr1
+; CHECK-NEXT:       - Name:            func_addr2
 ; CHECK-NEXT:         Kind:            GLOBAL
 ; CHECK-NEXT:         Index:           4
+; CHECK-NEXT:       - Name:            data_addr1
+; CHECK-NEXT:         Kind:            GLOBAL
+; CHECK-NEXT:         Index:           5
 ; CHECK-NEXT:   - Type:            ELEM
 ; CHECK-NEXT:     Segments:
 ; CHECK-NEXT:       - Offset:
@@ -119,11 +137,16 @@
 ; CHECK-NEXT:       - Type:            R_WEBASSEMBLY_FUNCTION_INDEX_LEB
 ; CHECK-NEXT:         Index:           1
 ; CHECK-NEXT:         Offset:          0x00000013
+; CHECK-NEXT:       - Type:            R_WEBASSEMBLY_MEMORY_ADDR_SLEB
+; CHECK-NEXT:         Index:           2
+; CHECK-NEXT:         Offset:          0x0000001F
 ; CHECK-NEXT:     Functions:
 ; CHECK-NEXT:       - Locals:
-; CHECK-NEXT:         Body:          4180808080001080808080000B
+; CHECK-NEXT:         Body:            4180808080001080808080000B
 ; CHECK-NEXT:       - Locals:
-; CHECK-NEXT:         Body:          1081808080001A41010B
+; CHECK-NEXT:         Body:            1081808080001A41010B
+; CHECK-NEXT:       - Locals:
+; CHECK-NEXT:         Body:            4194808080000B
 ; CHECK-NEXT:   - Type:            DATA
 ; CHECK-NEXT:     Relocations:
 ; CHECK-NEXT:       - Type:            R_WEBASSEMBLY_TABLE_INDEX_I32
@@ -160,26 +183,43 @@
 ; CHECK-NEXT:           Opcode:          I32_CONST
 ; CHECK-NEXT:           Value:           16
 ; CHECK-NEXT:         Content:         FFFFFFFF
+; CHECK-NEXT:       - SectionOffset:   45
+; CHECK-NEXT:         MemoryIndex:     0
+; CHECK-NEXT:         Offset:
+; CHECK-NEXT:           Opcode:          I32_CONST
+; CHECK-NEXT:           Value:           20
+; CHECK-NEXT:         Content:         '616263'
 ; CHECK-NEXT:   - Type:            CUSTOM
 ; CHECK-NEXT:     Name:            linking
-; CHECK-NEXT:     DataSize:        20
+; CHECK-NEXT:     DataSize:        23
 ; CHECK-NEXT:     SegmentInfo:
 ; CHECK-NEXT:       - Index:           0
 ; CHECK-NEXT:         Name:            .rodata.hello_str
 ; CHECK-NEXT:         Alignment:       1
-; CHECK-NEXT:         Flags:           [ ]
+; CHECK-NEXT:         Flags:           [  ]
 ; CHECK-NEXT:       - Index:           1
 ; CHECK-NEXT:         Name:            .data.func_addr1
 ; CHECK-NEXT:         Alignment:       4
-; CHECK-NEXT:         Flags:           [ ]
+; CHECK-NEXT:         Flags:           [  ]
 ; CHECK-NEXT:       - Index:           2
 ; CHECK-NEXT:         Name:            .data.func_addr2
 ; CHECK-NEXT:         Alignment:       4
-; CHECK-NEXT:         Flags:           [ ]
+; CHECK-NEXT:         Flags:           [  ]
 ; CHECK-NEXT:       - Index:           3
 ; CHECK-NEXT:         Name:            .data.data_addr1
 ; CHECK-NEXT:         Alignment:       8
-; CHECK-NEXT:         Flags:           [ ]
+; CHECK-NEXT:         Flags:           [  ]
+; CHECK-NEXT:       - Index:           4
+; CHECK-NEXT:         Name:            .rodata.data_comdat
+; CHECK-NEXT:         Alignment:       1
+; CHECK-NEXT:         Flags:           [  ]
+; CHECK-NEXT:     Comdats:
+; CHECK-NEXT:       - Name:            func_comdat
+; CHECK-NEXT:         Entries:
+; CHECK-NEXT:           - Kind:            FUNCTION
+; CHECK-NEXT:             Index:           4
+; CHECK-NEXT:           - Kind:            DATA
+; CHECK-NEXT:             Index:           4
 ; CHECK-NEXT:   - Type:            CUSTOM
 ; CHECK-NEXT:     Name:            name
 ; CHECK-NEXT:     FunctionNames:
Index: wasm/InputChunks.h
===================================================================
--- wasm/InputChunks.h
+++ wasm/InputChunks.h
@@ -42,6 +42,7 @@
   virtual const uint8_t *getData() const = 0;
   virtual uint32_t getSize() const = 0;
   virtual uint32_t getInputSectionOffset() const = 0;
+  virtual StringRef getComdat() const = 0;
 
   int32_t OutputOffset = 0;
   int32_t InputOffset = 0;
@@ -82,6 +83,8 @@
   uint32_t getInputSectionOffset() const override {
     return Segment.SectionOffset;
   }
+  StringRef getComdat() const override { return Segment.Data.Comdat; }
+
   uint32_t getAlignment() const { return Segment.Data.Alignment; }
   uint32_t startVA() const { return Segment.Data.Offset.Value.Int32; }
   uint32_t endVA() const { return startVA() + getSize(); }
@@ -111,6 +114,7 @@
   uint32_t getInputSectionOffset() const override {
     return Function.CodeSectionOffset;
   };
+  StringRef getComdat() const override { return Function.Comdat; }
 
   uint32_t getOutputIndex() const { return OutputIndex.getValue(); };
   bool hasOutputIndex() const { return OutputIndex.hasValue(); };
Index: wasm/InputFiles.cpp
===================================================================
--- wasm/InputFiles.cpp
+++ wasm/InputFiles.cpp
@@ -172,6 +172,9 @@
   ArrayRef<WasmSignature> Types = WasmObj->types();
   ArrayRef<WasmGlobal> Globals = WasmObj->globals();
 
+  for (const auto &C : WasmObj->comdats())
+    Symtab->addComdat(C, this);
+
   FunctionSymbols.resize(NumFunctionImports + Funcs.size());
   GlobalSymbols.resize(NumGlobalImports + Globals.size());
 
@@ -236,7 +239,9 @@
   // the weak symbol), then it's discardable.  We aren't considering here
   // whether the Symbol is actually ever called.
   for (uint32_t I = 0; I < Funcs.size(); ++I) {
-    if (!ReachedFunctions[I])
+    StringRef Comdat = Functions[I]->getComdat();
+    ObjFile *ComdatFile = Comdat.empty() ? this : Symtab->findComdat(Comdat);
+    if (!ReachedFunctions[I] || ComdatFile != this)
       Functions[I]->Discarded = true;
   }
   for (uint32_t I = 0; I < Globals.size(); ++I) {
@@ -249,6 +254,11 @@
     if (!ReachedGlobals[I] && Seg->isCoveredByGlobal(Globals[I]))
       Seg->Discarded = true;
   }
+  for (InputSegment *Seg : Segments) {
+    StringRef Comdat = Seg->getComdat();
+    if (!Comdat.empty() && Symtab->findComdat(Comdat) != this)
+      Seg->Discarded = true;
+  }
 
   // Populate `TableSymbols` with all symbols that are called indirectly
   uint32_t SegmentCount = WasmObj->elements().size();
Index: wasm/SymbolTable.h
===================================================================
--- wasm/SymbolTable.h
+++ wasm/SymbolTable.h
@@ -58,11 +58,15 @@
   Symbol *addDefinedGlobal(StringRef Name);
   void addLazy(ArchiveFile *F, const Archive::Symbol *Sym);
 
+  bool addComdat(StringRef Name, ObjFile *);
+  ObjFile *findComdat(StringRef Name) const;
+
 private:
   std::pair<Symbol *, bool> insert(StringRef Name);
 
   llvm::DenseMap<llvm::CachedHashStringRef, Symbol *> SymMap;
   std::vector<Symbol *> SymVector;
+  llvm::DenseMap<llvm::CachedHashStringRef, ObjFile *> ComdatMap;
 };
 
 extern SymbolTable *Symtab;
Index: wasm/SymbolTable.cpp
===================================================================
--- wasm/SymbolTable.cpp
+++ wasm/SymbolTable.cpp
@@ -225,3 +225,19 @@
     F->addMember(Sym);
   }
 }
+
+bool SymbolTable::addComdat(StringRef Name, ObjFile *F) {
+  DEBUG(dbgs() << "addComdat: " << Name << "\n");
+  ObjFile *&File = ComdatMap[CachedHashStringRef(Name)];
+  if (File) {
+    DEBUG(dbgs() << "COMDAT already defined\n");
+    return false;
+  }
+  File = F;
+  return true;
+}
+
+ObjFile *SymbolTable::findComdat(StringRef Name) const {
+  auto It = ComdatMap.find(CachedHashStringRef(Name));
+  return It == ComdatMap.end() ? nullptr : It->second;
+}
Index: wasm/Writer.cpp
===================================================================
--- wasm/Writer.cpp
+++ wasm/Writer.cpp
@@ -24,6 +24,7 @@
 #include "llvm/Support/LEB128.h"
 
 #include <cstdarg>
+#include <map>
 
 #define DEBUG_TYPE "lld"
 
@@ -430,6 +431,42 @@
     SubSection.finalizeContents();
     SubSection.writeToStream(OS);
   }
+
+  struct ComdatEntry { unsigned Kind; uint32_t Index; };
+  std::map<StringRef,std::vector<ComdatEntry>> Comdats;
+  uint32_t NumFunctionImports = ImportedFunctions.size();
+
+  for (uint32_t I = 0; I < DefinedFunctions.size(); ++I) {
+    StringRef Comdat = DefinedFunctions[I]->getComdat();
+    if (!Comdat.empty())
+      Comdats[Comdat].emplace_back(
+          ComdatEntry{WASM_COMDAT_FUNCTION, I + NumFunctionImports});
+  }
+  for (uint32_t I = 0; I < Segments.size(); ++I) {
+    const auto &InputSegments = Segments[I]->InputSegments;
+    StringRef Comdat = InputSegments.empty() ? StringRef()
+                                             : InputSegments[0]->getComdat();
+    for (const InputSegment *IS : InputSegments)
+      assert(IS->getComdat() == Comdat);
+    if (!Comdat.empty())
+      Comdats[Comdat].emplace_back(ComdatEntry{WASM_COMDAT_DATA, I});
+  }
+
+  if (!Comdats.empty()) {
+    SubSection SubSection(WASM_COMDAT_INFO);
+    writeUleb128(SubSection.getStream(), Comdats.size(), "num comdats");
+    for (const auto &C : Comdats) {
+      writeStr(SubSection.getStream(), C.first, "comdat name");
+      writeUleb128(SubSection.getStream(), 0, "comdat flags"); // flags for future use
+      writeUleb128(SubSection.getStream(), C.second.size(), "num entries");
+      for (const ComdatEntry &Entry : C.second) {
+        writeUleb128(SubSection.getStream(), Entry.Kind, "entry kind");
+        writeUleb128(SubSection.getStream(), Entry.Index, "entry index");
+      }
+    }
+    SubSection.finalizeContents();
+    SubSection.writeToStream(OS);
+  }
 }
 
 // Create the custom "name" section containing debug symbol names.