Index: llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp
===================================================================
--- llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp
+++ llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp
@@ -2105,6 +2105,12 @@
     const std::string &UniqueModuleId) {
   assert(ExtendedGlobals.size() == MetadataInitializers.size());
 
+  // Putting globals in a comdat changes the semantic and potentially cause
+  // false negative odr violations at link time. If odr indicators are used, we
+  // keep the comdat sections, as link time odr violations will be dectected on
+  // the odr indicator symbols.
+  bool UseComdatForGlobalsGC = UseOdrIndicator;
+
   SmallVector<GlobalValue *, 16> MetadataGlobals(ExtendedGlobals.size());
   for (size_t i = 0; i < ExtendedGlobals.size(); i++) {
     GlobalVariable *G = ExtendedGlobals[i];
@@ -2114,7 +2120,8 @@
     Metadata->setMetadata(LLVMContext::MD_associated, MD);
     MetadataGlobals[i] = Metadata;
 
-    SetComdatForGlobalMetadata(G, Metadata, UniqueModuleId);
+    if(UseComdatForGlobalsGC)
+      SetComdatForGlobalMetadata(G, Metadata, UniqueModuleId);
   }
 
   // Update llvm.compiler.used, adding the new metadata globals. This is
Index: llvm/test/Instrumentation/AddressSanitizer/global_metadata.ll
===================================================================
--- llvm/test/Instrumentation/AddressSanitizer/global_metadata.ll
+++ llvm/test/Instrumentation/AddressSanitizer/global_metadata.ll
@@ -19,8 +19,8 @@
 
 ; Check that globals were instrumented:
 
-; CHECK: @global = global { i32, [60 x i8] } zeroinitializer, comdat, align 32
-; CHECK: @.str = internal constant { [14 x i8], [50 x i8] } { [14 x i8] c"Hello, world!\00", [50 x i8] zeroinitializer }, comdat($".str${{[01-9a-f]+}}"), align 32
+; CHECK: @global = global { i32, [60 x i8] } zeroinitializer, align 32
+; CHECK: @.str = internal constant { [14 x i8], [50 x i8] } { [14 x i8] c"Hello, world!\00", [50 x i8] zeroinitializer }, align 32
 
 ; Check emitted location descriptions:
 ; CHECK: [[VARNAME:@___asan_gen_.[0-9]+]] = private unnamed_addr constant [7 x i8] c"global\00", align 1
Index: llvm/test/Instrumentation/AddressSanitizer/global_with_comdat.ll
===================================================================
--- /dev/null
+++ llvm/test/Instrumentation/AddressSanitizer/global_with_comdat.ll
@@ -0,0 +1,100 @@
+; Check that we disable the use of comdat sections for the garbage collection
+; of globals.
+; This is to avoid false negative ODR violations detection at link time.
+; We keep using comdats for garbage collection if odr indicators are
+; enabled as indicator symbols will cause link time odr violations.
+; This is to fix PR 47925.
+;
+; RUN: opt < %s -asan -asan-module -enable-new-pm=0 -asan-globals-live-support=1 -S | FileCheck %s --check-prefixes=CHECK,NOCOMDAT
+; RUN: opt < %s -passes='asan-pipeline'             -asan-globals-live-support=1 -S | FileCheck %s --check-prefixes=CHECK,NOCOMDAT
+; Check that enabling odr indicators enables comdat for globals.
+; RUN: opt < %s -asan -asan-module -enable-new-pm=0 -asan-globals-live-support=1 -asan-use-odr-indicator=1 -S | FileCheck %s --check-prefixes=CHECK,COMDAT
+; RUN: opt < %s -passes='asan-pipeline'             -asan-globals-live-support=1 -asan-use-odr-indicator=1 -S | FileCheck %s --check-prefixes=CHECK,COMDAT
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+; Globals:
+@global = global i32 0, align 4
+@dyn_init_global = global i32 0, align 4
+@blacklisted_global = global i32 0, align 4
+@_ZZ4funcvE10static_var = internal global i32 0, align 4
+@.str = private unnamed_addr constant [14 x i8] c"Hello, world!\00", align 1
+@llvm.global_ctors = appending global [1 x { i32, void ()*, i8* }] [{ i32, void ()*, i8* } { i32 65535, void ()* @_GLOBAL__sub_I_asan_globals.cpp, i8* null }]
+
+; Check that globals were instrumented:
+
+; COMDAT: $global = comdat any
+; COMDAT: $dyn_init_global = comdat any
+; COMDAT: $"_ZZ4funcvE10static_var${{[01-9a-f]+}}" = comdat any
+; COMDAT: $".str${{[01-9a-f]+}}" = comdat any
+
+; NOCOMDAT-NOT: $global = comdat any
+; NOCOMDAT-NOT: $dyn_init_global = comdat any
+; NOCOMDAT-NOT: $"_ZZ4funcvE10static_var${{[01-9a-f]+}}" = comdat any
+; NOCOMDAT-NOT: $".str${{[01-9a-f]+}}" = comdat any
+
+; COMDAT: @global = global { i32, [60 x i8] } zeroinitializer, comdat, align 32
+; COMDAT: @dyn_init_global = global { i32, [60 x i8] } zeroinitializer, comdat, align 32
+; COMDAT: @_ZZ4funcvE10static_var = internal global { i32, [60 x i8] } zeroinitializer, comdat($"_ZZ4funcvE10static_var${{[01-9a-f]+}}"), align 32
+; COMDAT: @.str = internal constant { [14 x i8], [50 x i8] } { [14 x i8] c"Hello, world!\00", [50 x i8] zeroinitializer }, comdat($".str${{[01-9a-f]+}}"), align 32
+
+; NOCOMDAT: @global = global { i32, [60 x i8] } zeroinitializer, align 32
+; NOCOMDAT: @dyn_init_global = global { i32, [60 x i8] } zeroinitializer, align 32
+; NOCOMDAT: @_ZZ4funcvE10static_var = internal global { i32, [60 x i8] } zeroinitializer, align 32
+; NOCOMDAT: @.str = internal constant { [14 x i8], [50 x i8] } { [14 x i8] c"Hello, world!\00", [50 x i8] zeroinitializer }, align 32
+
+; Check emitted location descriptions:
+; CHECK: [[VARNAME:@___asan_gen_.[0-9]+]] = private unnamed_addr constant [7 x i8] c"global\00", align 1
+; CHECK: [[FILENAME:@___asan_gen_.[0-9]+]] = private unnamed_addr constant [22 x i8] c"/tmp/asan-globals.cpp\00", align 1
+; CHECK: [[LOCDESCR:@___asan_gen_.[0-9]+]] = private unnamed_addr constant { [22 x i8]*, i32, i32 } { [22 x i8]* [[FILENAME]], i32 5, i32 5 }
+; COMDAT: @__asan_global_global = {{.*}}i64 ptrtoint ({ i32, [60 x i8] }* @global to i64){{.*}} section "asan_globals"{{.*}}, !associated
+; COMDAT: @__asan_global_.str = {{.*}}i64 ptrtoint ({ [14 x i8], [50 x i8] }* @{{.str|1}} to i64){{.*}} section "asan_globals"{{.*}}, !associated
+
+; The metadata has to be inserted to llvm.compiler.used to avoid being stripped
+; during LTO.
+; CHECK: @llvm.compiler.used {{.*}} @__asan_global_global {{.*}} section "llvm.metadata"
+
+; Check that location descriptors and global names were passed into __asan_register_globals:
+; CHECK: call void @__asan_register_elf_globals(i64 ptrtoint (i64* @___asan_globals_registered to i64), i64 ptrtoint (i64* @__start_asan_globals to i64), i64 ptrtoint (i64* @__stop_asan_globals to i64))
+
+; Function Attrs: nounwind sanitize_address
+define internal void @__cxx_global_var_init() #0 section ".text.startup" {
+entry:
+  %0 = load i32, i32* @global, align 4
+  store i32 %0, i32* @dyn_init_global, align 4
+  ret void
+}
+
+; Function Attrs: nounwind sanitize_address
+define void @_Z4funcv() #1 {
+entry:
+  %literal = alloca i8*, align 8
+  store i8* getelementptr inbounds ([14 x i8], [14 x i8]* @.str, i32 0, i32 0), i8** %literal, align 8
+  ret void
+}
+
+; Function Attrs: nounwind sanitize_address
+define internal void @_GLOBAL__sub_I_asan_globals.cpp() #0 section ".text.startup" {
+entry:
+  call void @__cxx_global_var_init()
+  ret void
+}
+
+attributes #0 = { nounwind sanitize_address }
+attributes #1 = { nounwind sanitize_address "less-precise-fpmad"="false" "frame-pointer"="none" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "no-realign-stack" "stack-protector-buffer-size"="8" "unsafe-fp-math"="false" "use-soft-float"="false" }
+
+!llvm.asan.globals = !{!0, !1, !2, !3, !4}
+!llvm.ident = !{!5}
+
+!0 = !{i32* @global, !6, !"global", i1 false, i1 false}
+!1 = !{i32* @dyn_init_global, !7, !"dyn_init_global", i1 true, i1 false}
+!2 = !{i32* @blacklisted_global, null, null, i1 false, i1 true}
+!3 = !{i32* @_ZZ4funcvE10static_var, !8, !"static_var", i1 false, i1 false}
+!4 = !{[14 x i8]* @.str, !9, !"<string literal>", i1 false, i1 false}
+
+!5 = !{!"clang version 3.5.0 (211282)"}
+
+!6 = !{!"/tmp/asan-globals.cpp", i32 5, i32 5}
+!7 = !{!"/tmp/asan-globals.cpp", i32 7, i32 5}
+!8 = !{!"/tmp/asan-globals.cpp", i32 12, i32 14}
+!9 = !{!"/tmp/asan-globals.cpp", i32 14, i32 25}
Index: llvm/test/Instrumentation/AddressSanitizer/instrument-section-invalid-c-ident.ll
===================================================================
--- llvm/test/Instrumentation/AddressSanitizer/instrument-section-invalid-c-ident.ll
+++ llvm/test/Instrumentation/AddressSanitizer/instrument-section-invalid-c-ident.ll
@@ -11,7 +11,7 @@
 @data2 = dso_local global i32 2, align 4
 @__invalid$c$name_sym_data1 = internal constant i8* bitcast (i32* @data1 to i8*), section "invalid$c$name", align 8
 @__invalid$c$name_sym_data2 = internal constant i8* bitcast (i32* @data2 to i8*), section "invalid$c$name", align 8
-; CHECK: @"__invalid$c$name_sym_data1" = internal constant{{.*}}, section "invalid$c$name", comdat
-; CHECK-NEXT: @"__invalid$c$name_sym_data2" = internal constant{{.*}}, section "invalid$c$name", comdat
+; CHECK: @"__invalid$c$name_sym_data1" = internal constant{{.*}}, section "invalid$c$name"
+; CHECK-NEXT: @"__invalid$c$name_sym_data2" = internal constant{{.*}}, section "invalid$c$name"
 ; CHECK: @"__asan_global___invalid$c$name_sym_data1"
 ; CHECK-NEXT: @"__asan_global___invalid$c$name_sym_data2"