Index: flang/test/Fir/global.fir
===================================================================
--- flang/test/Fir/global.fir
+++ flang/test/Fir/global.fir
@@ -1,6 +1,9 @@
 // RUN: tco %s | FileCheck %s
 // RUN: %flang_fc1 -emit-llvm  %s -o - | FileCheck %s
 
+// CHECK: $w_i86 = comdat any
+// CHECK: $str1 = comdat any
+
 // CHECK: @g_i0 = global i32 0
 fir.global @g_i0 : i32 {
   %1 = arith.constant 0 : i32
@@ -25,11 +28,11 @@
 // CHECK: @C_i511 = common global i32 0
 fir.global common @C_i511 (0:i32) : i32
 
-// CHECK: @w_i86 = weak global i32 86
+// CHECK: @w_i86 = weak global i32 86, comdat
 fir.global weak @w_i86 (86:i32) : i32
 
-// CHECK: @str1 = global [6 x i8] c"Hello!"
-fir.global @str1 : !fir.char<1,6> {
+// CHECK: @str1 = linkonce global [6 x i8] c"Hello!", comdat
+fir.global linkonce @str1 : !fir.char<1,6> {
   %1 = fir.string_lit "Hello!"(6) : !fir.char<1,6>
   fir.has_value %1 : !fir.char<1,6>
 }
Index: mlir/lib/Target/LLVMIR/ModuleTranslation.cpp
===================================================================
--- mlir/lib/Target/LLVMIR/ModuleTranslation.cpp
+++ mlir/lib/Target/LLVMIR/ModuleTranslation.cpp
@@ -672,6 +672,11 @@
     if (op.getSection().hasValue())
       var->setSection(*op.getSection());
 
+    auto TargetTriple = llvm::Triple(llvmModule->getTargetTriple());
+    if (var->isWeakForLinker() && !var->hasCommonLinkage() &&
+        !var->isDeclarationForLinker() && TargetTriple.supportsCOMDAT())
+      var->setComdat(llvmModule->getOrInsertComdat(var->getName()));
+
     addRuntimePreemptionSpecifier(op.getDsoLocal(), var);
 
     Optional<uint64_t> alignment = op.getAlignment();
Index: mlir/test/Target/LLVMIR/llvmir.mlir
===================================================================
--- mlir/test/Target/LLVMIR/llvmir.mlir
+++ mlir/test/Target/LLVMIR/llvmir.mlir
@@ -1,5 +1,10 @@
 // RUN: mlir-translate -mlir-to-llvmir -split-input-file %s | FileCheck %s
 
+// CHECK: $linkonce = comdat any
+// CHECK: $weak = comdat any
+// CHECK: $linkonce_odr = comdat any
+// CHECK: $weak_odr = comdat any
+
 // CHECK: @global_aligned32 = private global i64 42, align 32
 "llvm.mlir.global"() ({}) {sym_name = "global_aligned32", global_type = i64, value = 42 : i64, linkage = #llvm.linkage<private>, alignment = 32} : () -> ()
 
@@ -93,9 +98,9 @@
 llvm.mlir.global internal @internal(42 : i32) : i32
 // CHECK: @available_externally = available_externally global i32 42
 llvm.mlir.global available_externally @available_externally(42 : i32) : i32
-// CHECK: @linkonce = linkonce global i32 42
+// CHECK: @linkonce = linkonce global i32 42, comdat
 llvm.mlir.global linkonce @linkonce(42 : i32) : i32
-// CHECK: @weak = weak global i32 42
+// CHECK: @weak = weak global i32 42, comdat
 llvm.mlir.global weak @weak(42 : i32) : i32
 // CHECK: @common = common global i32 0
 llvm.mlir.global common @common(0 : i32) : i32
@@ -103,9 +108,9 @@
 llvm.mlir.global appending @appending(dense<[1,2,3]> : tensor<3xi32>) : !llvm.array<3xi32>
 // CHECK: @extern_weak = extern_weak global i32
 llvm.mlir.global extern_weak @extern_weak() : i32
-// CHECK: @linkonce_odr = linkonce_odr global i32 42
+// CHECK: @linkonce_odr = linkonce_odr global i32 42, comdat
 llvm.mlir.global linkonce_odr @linkonce_odr(42 : i32) : i32
-// CHECK: @weak_odr = weak_odr global i32 42
+// CHECK: @weak_odr = weak_odr global i32 42, comdat
 llvm.mlir.global weak_odr @weak_odr(42 : i32) : i32
 // CHECK: @external = external global i32
 llvm.mlir.global external @external() : i32
@@ -1490,7 +1495,8 @@
 
 // -----
 
-// CHECK: @forward_use_of_address = linkonce global ptr @address_declared_after_use
+// CHECK: $forward_use_of_address = comdat any
+// CHECK: @forward_use_of_address = linkonce global ptr @address_declared_after_use, comdat
 llvm.mlir.global linkonce @forward_use_of_address() : !llvm.ptr<f32> {
   %0 = llvm.mlir.addressof @address_declared_after_use : !llvm.ptr<f32>
   llvm.return %0 : !llvm.ptr<f32>
@@ -1500,7 +1506,8 @@
 
 // -----
 
-// CHECK: @take_self_address = linkonce global { i32, ptr } {{.*}} ptr @take_self_address
+// CHECK: $take_self_address = comdat any
+// CHECK: @take_self_address = linkonce global { i32, ptr } {{.*}} ptr @take_self_address }, comdat
 llvm.mlir.global linkonce @take_self_address() : !llvm.struct<(i32, !llvm.ptr<i32>)> {
   %z32 = llvm.mlir.constant(0 : i32) : i32
   %0 = llvm.mlir.undef : !llvm.struct<(i32, !llvm.ptr<i32>)>