diff --git a/llvm/lib/Analysis/GlobalsModRef.cpp b/llvm/lib/Analysis/GlobalsModRef.cpp
--- a/llvm/lib/Analysis/GlobalsModRef.cpp
+++ b/llvm/lib/Analysis/GlobalsModRef.cpp
@@ -913,6 +913,10 @@
   ModRefInfo ConservativeResult =
       Call->onlyReadsMemory() ? ModRefInfo::Ref : ModRefInfo::ModRef;
 
+  if (Function *F = Call->getCalledFunction())
+    if (!F->hasNoSync())
+      return ConservativeResult;
+
   // Iterate through all the arguments to the called function. If any argument
   // is based on GV, return the conservative result.
   for (auto &A : Call->args()) {
diff --git a/llvm/test/Analysis/GlobalsModRef/functions_without_nosync.ll b/llvm/test/Analysis/GlobalsModRef/functions_without_nosync.ll
new file mode 100644
--- /dev/null
+++ b/llvm/test/Analysis/GlobalsModRef/functions_without_nosync.ll
@@ -0,0 +1,37 @@
+; RUN: opt -globals-aa -gvn -S < %s | FileCheck %s
+;
+; Functions w/o `nosync` attribute may communicate via memory and must be
+; treated conservatively.
+
+target datalayout = "e-i64:64-i128:128-v16:16-v32:32-n16:32:64"
+target triple = "nvptx64-nvidia-cuda"
+
+@s = internal local_unnamed_addr addrspace(3) global i32 undef, align 4
+
+; CHECK-LABEL: @bar_sync
+; CHECK: store
+; CHECK: tail call void @llvm.nvvm.bar.sync(i32 0)
+; CHECK: load
+define dso_local i32 @bar_sync(i32 %0) local_unnamed_addr {
+  store i32 %0, i32* addrspacecast (i32 addrspace(3)* @s to i32*), align 4
+  tail call void @llvm.nvvm.bar.sync(i32 0)
+  %2 = load i32, i32* addrspacecast (i32 addrspace(3)* @s to i32*), align 4
+  ret i32 %2
+}
+
+declare void @llvm.nvvm.bar.sync(i32) #0
+
+; CHECK-LABEL: @barrier0
+; CHECK: store
+; CHECK: tail call void @llvm.nvvm.barrier0()
+; CHECK: load
+define dso_local i32 @barrier0(i32 %0) local_unnamed_addr  {
+  store i32 %0, i32* addrspacecast (i32 addrspace(3)* @s to i32*), align 4
+  tail call void @llvm.nvvm.barrier0()
+  %2 = load i32, i32* addrspacecast (i32 addrspace(3)* @s to i32*), align 4
+  ret i32 %2
+}
+
+declare void @llvm.nvvm.barrier0() #0
+
+attributes #0 = { convergent nounwind }