[IR] Add support for memory attribute

This implements IR and bitcode support for the memory attribute,
as specified in https://reviews.llvm.org/D135597.

The new attribute is not used for anything yet (and as such, the
old memory attributes are unaffected).

Differential Revision: https://reviews.llvm.org/D135592

llvm/lib/Bitcode/Reader/BitcodeReader.cpp

@@ -55,6 +55,7 @@
 #include "llvm/IR/IntrinsicsARM.h"
 #include "llvm/IR/LLVMContext.h"
 #include "llvm/IR/Metadata.h"
+#include "llvm/IR/ModRef.h"
 #include "llvm/IR/Module.h"
 #include "llvm/IR/ModuleSummaryIndex.h"
 #include "llvm/IR/Operator.h"
@@ -1878,6 +1879,8 @@ static Attribute::AttrKind getAttrFromCode(uint64_t Code) {
     return Attribute::InReg;
   case bitc::ATTR_KIND_JUMP_TABLE:
     return Attribute::JumpTable;
+  case bitc::ATTR_KIND_MEMORY:
+    return Attribute::Memory;
   case bitc::ATTR_KIND_MIN_SIZE:
     return Attribute::MinSize;
   case bitc::ATTR_KIND_NAKED:
@@ -2122,6 +2125,8 @@ Error BitcodeReader::parseAttributeGroupBlock() {
             B.addUWTableAttr(UWTableKind(Record[++i]));
           else if (Kind == Attribute::AllocKind)
             B.addAllocKindAttr(static_cast<AllocFnKind>(Record[++i]));
+          else if (Kind == Attribute::Memory)
+            B.addMemoryAttr(MemoryEffects::createFromIntValue(Record[++i]));
         } else if (Record[i] == 3 || Record[i] == 4) { // String attribute
           bool HasValue = (Record[i++] == 4);
           SmallString<64> KindStr;