Index: llvm/docs/LangRef.rst
===================================================================
--- llvm/docs/LangRef.rst
+++ llvm/docs/LangRef.rst
@@ -1907,6 +1907,10 @@
 
     If an argmemonly function reads or writes memory other than the pointer
     arguments, or has other side-effects, the behavior is undefined.
+``globalmemonly``
+   This attribute indicates that the only memory accessed inside a function,
+   that is visible to the callee, is global memory. If the function reads or
+   writes other memory that is visible to the callee, the behavior is undefined.
 ``returns_twice``
     This attribute indicates that this function can return twice. The C
     ``setjmp`` is an example of such a function. The compiler disables
Index: llvm/include/llvm/AsmParser/LLToken.h
===================================================================
--- llvm/include/llvm/AsmParser/LLToken.h
+++ llvm/include/llvm/AsmParser/LLToken.h
@@ -252,6 +252,7 @@
   kw_immarg,
   kw_byref,
   kw_mustprogress,
+  kw_globalmemonly,
 
   kw_type,
   kw_opaque,
Index: llvm/include/llvm/Bitcode/LLVMBitCodes.h
===================================================================
--- llvm/include/llvm/Bitcode/LLVMBitCodes.h
+++ llvm/include/llvm/Bitcode/LLVMBitCodes.h
@@ -672,6 +672,7 @@
   ATTR_KIND_NO_SANITIZE_COVERAGE = 76,
   ATTR_KIND_ELEMENTTYPE = 77,
   ATTR_KIND_DISABLE_SANITIZER_INSTRUMENTATION = 78,
+  ATTR_KIND_GLOBALMEMONLY = 79
 };
 
 enum ComdatSelectionKindCodes {
Index: llvm/include/llvm/IR/Attributes.td
===================================================================
--- llvm/include/llvm/IR/Attributes.td
+++ llvm/include/llvm/IR/Attributes.td
@@ -92,6 +92,9 @@
 /// Provide pointer element type to intrinsic.
 def ElementType : TypeAttr<"elementtype", [ParamAttr]>;
 
+/// Function can only access or modify global variables
+def GlobalMemOnly : EnumAttr<"globalmemonly", [FnAttr]>;
+
 /// Function may only access memory that is inaccessible from IR.
 def InaccessibleMemOnly : EnumAttr<"inaccessiblememonly", [FnAttr]>;
 
Index: llvm/lib/AsmParser/LLLexer.cpp
===================================================================
--- llvm/lib/AsmParser/LLLexer.cpp
+++ llvm/lib/AsmParser/LLLexer.cpp
@@ -708,6 +708,7 @@
   KEYWORD(immarg);
   KEYWORD(byref);
   KEYWORD(mustprogress);
+  KEYWORD(globalmemonly);
 
   KEYWORD(type);
   KEYWORD(opaque);
Index: llvm/lib/Bitcode/Reader/BitcodeReader.cpp
===================================================================
--- llvm/lib/Bitcode/Reader/BitcodeReader.cpp
+++ llvm/lib/Bitcode/Reader/BitcodeReader.cpp
@@ -1533,6 +1533,8 @@
     return Attribute::MustProgress;
   case bitc::ATTR_KIND_HOT:
     return Attribute::Hot;
+  case bitc::ATTR_KIND_GLOBALMEMONLY:
+    return Attribute::GlobalMemOnly;
   }
 }
 
Index: llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
===================================================================
--- llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
+++ llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
@@ -764,6 +764,8 @@
     return bitc::ATTR_KIND_BYREF;
   case Attribute::MustProgress:
     return bitc::ATTR_KIND_MUSTPROGRESS;
+  case Attribute::GlobalMemOnly:
+    return bitc::ATTR_KIND_GLOBALMEMONLY;
   case Attribute::EndAttrKinds:
     llvm_unreachable("Can not encode end-attribute kinds marker.");
   case Attribute::None:
Index: llvm/lib/Transforms/Utils/CodeExtractor.cpp
===================================================================
--- llvm/lib/Transforms/Utils/CodeExtractor.cpp
+++ llvm/lib/Transforms/Utils/CodeExtractor.cpp
@@ -904,6 +904,7 @@
       case Attribute::Dereferenceable:
       case Attribute::DereferenceableOrNull:
       case Attribute::ElementType:
+      case Attribute::GlobalMemOnly:
       case Attribute::InAlloca:
       case Attribute::InReg:
       case Attribute::InaccessibleMemOnly:
Index: llvm/test/Bitcode/attributes.ll
===================================================================
--- llvm/test/Bitcode/attributes.ll
+++ llvm/test/Bitcode/attributes.ll
@@ -478,6 +478,12 @@
         ret void;
 }
 
+; CHECK: define void @f81() #51
+define void @f81() globalmemonly
+{
+        ret void;
+}
+
 ; CHECK: attributes #0 = { noreturn }
 ; CHECK: attributes #1 = { nounwind }
 ; CHECK: attributes #2 = { readnone }
@@ -529,4 +535,5 @@
 ; CHECK: attributes #48 = { nosanitize_coverage }
 ; CHECK: attributes #49 = { noprofile }
 ; CHECK: attributes #50 = { disable_sanitizer_instrumentation }
+; CHECK: attributes #51 = { globalmemonly }
 ; CHECK: attributes #[[NOBUILTIN]] = { nobuiltin }