diff --git a/llvm/lib/AsmParser/LLParser.cpp b/llvm/lib/AsmParser/LLParser.cpp
--- a/llvm/lib/AsmParser/LLParser.cpp
+++ b/llvm/lib/AsmParser/LLParser.cpp
@@ -7671,7 +7671,8 @@
     return tokError("atomicrmw cannot be unordered");
   if (!Ptr->getType()->isPointerTy())
     return error(PtrLoc, "atomicrmw operand must be a pointer");
-  if (cast<PointerType>(Ptr->getType())->getElementType() != Val->getType())
+  if (!cast<PointerType>(Ptr->getType())
+           ->isOpaqueOrPointeeTypeMatches(Val->getType()))
     return error(ValLoc, "atomicrmw value and pointer type do not match");
 
   if (Operation == AtomicRMWInst::Xchg) {
diff --git a/llvm/lib/Bitcode/Reader/BitcodeReader.cpp b/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
--- a/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
+++ b/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
@@ -5251,9 +5251,11 @@
         if (popValue(Record, OpNum, NextValueNo,
                      getPointerElementFlatType(FullTy), Val))
           return error("Invalid record");
+        FullTy = getPointerElementFlatType(FullTy);
       } else {
         if (getValueTypePair(Record, OpNum, NextValueNo, Val))
           return error("Invalid record");
+        FullTy = Val->getType();
       }
 
       if (!(NumRecords == (OpNum + 4) || NumRecords == (OpNum + 5)))
@@ -5286,7 +5288,6 @@
             Align(TheModule->getDataLayout().getTypeStoreSize(Val->getType()));
 
       I = new AtomicRMWInst(Operation, Ptr, Val, *Alignment, Ordering, SSID);
-      FullTy = getPointerElementFlatType(FullTy);
       cast<AtomicRMWInst>(I)->setVolatile(IsVol);
 
       InstructionList.push_back(I);
diff --git a/llvm/lib/IR/Instructions.cpp b/llvm/lib/IR/Instructions.cpp
--- a/llvm/lib/IR/Instructions.cpp
+++ b/llvm/lib/IR/Instructions.cpp
@@ -1602,9 +1602,9 @@
          "All operands must be non-null!");
   assert(getOperand(0)->getType()->isPointerTy() &&
          "Ptr must have pointer type!");
-  assert(getOperand(1)->getType() ==
-         cast<PointerType>(getOperand(0)->getType())->getElementType()
-         && "Ptr must be a pointer to Val type!");
+  assert(cast<PointerType>(getOperand(0)->getType())
+             ->isOpaqueOrPointeeTypeMatches(getOperand(1)->getType()) &&
+         "Ptr must be a pointer to Val type!");
   assert(Ordering != AtomicOrdering::NotAtomic &&
          "AtomicRMW instructions must be atomic!");
 }
diff --git a/llvm/test/Assembler/atomicrmw.ll b/llvm/test/Assembler/atomicrmw.ll
new file mode 100644
--- /dev/null
+++ b/llvm/test/Assembler/atomicrmw.ll
@@ -0,0 +1,18 @@
+; RUN: llvm-as %s -o - | llvm-dis | FileCheck %s
+
+; Make sure that we can parse an atomicrmw with an operand defined later in the function.
+
+; CHECK: @f
+; CHECK: atomicrmw
+define void @f() {
+  entry:
+    br label %def
+
+  use:
+    %x = atomicrmw add i32* undef, i32 %y monotonic
+    ret void
+
+  def:
+    %y = add i32 undef, undef
+    br i1 undef, label %use, label %use
+}
diff --git a/llvm/test/Assembler/opaque-ptr.ll b/llvm/test/Assembler/opaque-ptr.ll
--- a/llvm/test/Assembler/opaque-ptr.ll
+++ b/llvm/test/Assembler/opaque-ptr.ll
@@ -56,3 +56,11 @@
     %val_success = cmpxchg ptr %p, i32 %a, i32 %b acq_rel monotonic
     ret void
 }
+
+; CHECK: define void @atomicrmw(ptr %a, i32 %i)
+; CHECK:     %b = atomicrmw add ptr %a, i32 %i acquire
+; CHECK:     ret void
+define void @atomicrmw(ptr %a, i32 %i) {
+    %b = atomicrmw add ptr %a, i32 %i acquire
+    ret void
+}
diff --git a/llvm/test/Verifier/opaque-ptr.ll b/llvm/test/Verifier/opaque-ptr.ll
--- a/llvm/test/Verifier/opaque-ptr.ll
+++ b/llvm/test/Verifier/opaque-ptr.ll
@@ -17,3 +17,9 @@
     %val_success = cmpxchg ptr %p, i32 %a, i32 %b acq_rel monotonic
     ret void
 }
+
+; CHECK: @atomicrmw
+define void @atomicrmw(ptr %a, i32 %i) {
+    %b = atomicrmw add ptr %a, i32 %i acquire
+    ret void
+}