diff --git a/llvm/lib/Transforms/Coroutines/CoroSplit.cpp b/llvm/lib/Transforms/Coroutines/CoroSplit.cpp
--- a/llvm/lib/Transforms/Coroutines/CoroSplit.cpp
+++ b/llvm/lib/Transforms/Coroutines/CoroSplit.cpp
@@ -871,11 +871,17 @@
                                   OrigF.getParent()->end(), ActiveSuspend);
   }
 
-  // Replace all args with undefs. The buildCoroutineFrame algorithm already
-  // rewritten access to the args that occurs after suspend points with loads
-  // and stores to/from the coroutine frame.
-  for (Argument &A : OrigF.args())
-    VMap[&A] = UndefValue::get(A.getType());
+  // Replace all args with dummy instructions. If an argument is the old frame
+  // pointer, the dummy will be replaced by the new frame pointer once it is
+  // computed below. Uses of all other arguments should have already been
+  // rewritten by buildCoroutineFrame() to use loads/stores on the coroutine
+  // frame.
+  SmallVector<Instruction *> DummyArgs;
+  for (Argument &A : OrigF.args()) {
+    DummyArgs.push_back(
+        new BitCastInst(UndefValue::get(A.getType()), A.getType()));
+    VMap[&A] = DummyArgs.back();
+  }
 
   SmallVector<ReturnInst *, 4> Returns;
 
@@ -1019,6 +1025,13 @@
   if (OldVFrame != NewVFrame)
     OldVFrame->replaceAllUsesWith(NewVFrame);
 
+  // All uses of the arguments should have been resolved by this point,
+  // so we can safely remove the dummy values.
+  for (Instruction *DummyArg : DummyArgs) {
+    DummyArg->replaceAllUsesWith(UndefValue::get(DummyArg->getType()));
+    DummyArg->deleteValue();
+  }
+
   switch (Shape.ABI) {
   case coro::ABI::Switch:
     // Rewrite final suspend handling as it is not done via switch (allows to
diff --git a/llvm/test/Transforms/Coroutines/coro-retcon-alloca-opaque-ptr.ll b/llvm/test/Transforms/Coroutines/coro-retcon-alloca-opaque-ptr.ll
new file mode 100644
--- /dev/null
+++ b/llvm/test/Transforms/Coroutines/coro-retcon-alloca-opaque-ptr.ll
@@ -0,0 +1,90 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+
+; RUN: opt < %s -enable-coroutines -passes='default<O2>' -opaque-pointers=1 -S | FileCheck %s
+
+target datalayout = "p:64:64:64"
+
+declare {i8*, i8*, i32} @prototype_f(i8*, i1)
+define {i8*, i8*, i32} @f(i8* %buffer, i32 %n) {
+; CHECK-LABEL: @f(
+; CHECK-NEXT:  coro.return:
+; CHECK-NEXT:    [[N_VAL_SPILL_ADDR:%.*]] = getelementptr inbounds [[F_FRAME:%.*]], ptr [[BUFFER:%.*]], i64 0, i32 1
+; CHECK-NEXT:    store i32 [[N:%.*]], ptr [[N_VAL_SPILL_ADDR]], align 4
+; CHECK-NEXT:    [[TMP0:%.*]] = tail call ptr @allocate(i32 [[N]])
+; CHECK-NEXT:    store ptr [[TMP0]], ptr [[BUFFER]], align 8
+; CHECK-NEXT:    [[TMP1:%.*]] = insertvalue { ptr, ptr, i32 } { ptr @f.resume.0, ptr undef, i32 undef }, ptr [[TMP0]], 1
+; CHECK-NEXT:    [[TMP2:%.*]] = insertvalue { ptr, ptr, i32 } [[TMP1]], i32 [[N]], 2
+; CHECK-NEXT:    ret { ptr, ptr, i32 } [[TMP2]]
+;
+entry:
+  %id = call token @llvm.coro.id.retcon(i32 1024, i32 8, i8* %buffer, i8* bitcast ({i8*, i8*, i32} (i8*, i1)* @prototype_f to i8*), i8* bitcast (i8* (i32)* @allocate to i8*), i8* bitcast (void (i8*)* @deallocate to i8*))
+  %hdl = call i8* @llvm.coro.begin(token %id, i8* null)
+  br label %loop
+
+loop:
+  %n.val = phi i32 [ %n, %entry ], [ %inc, %resume ]
+  %alloca = call token @llvm.coro.alloca.alloc.i32(i32 %n.val, i32 8)
+  %ptr = call i8* @llvm.coro.alloca.get(token %alloca)
+  %unwind = call i1 (...) @llvm.coro.suspend.retcon.i1(i8* %ptr, i32 %n.val)
+  call void @llvm.coro.alloca.free(token %alloca)
+  br i1 %unwind, label %cleanup, label %resume
+
+resume:
+  %inc = add i32 %n.val, 1
+  br label %loop
+
+cleanup:
+  call i1 @llvm.coro.end(i8* %hdl, i1 0)
+  unreachable
+}
+
+
+declare {i8*, i32} @prototype_g(i8*, i1)
+define {i8*, i32} @g(i8* %buffer, i32 %n) {
+; CHECK-LABEL: @g(
+; CHECK-NEXT:  coro.return:
+; CHECK-NEXT:    store i32 [[N:%.*]], ptr [[BUFFER:%.*]], align 4
+; CHECK-NEXT:    [[TMP0:%.*]] = zext i32 [[N]] to i64
+; CHECK-NEXT:    [[TMP1:%.*]] = alloca i8, i64 [[TMP0]], align 8
+; CHECK-NEXT:    tail call void @use(ptr nonnull [[TMP1]])
+; CHECK-NEXT:    [[TMP2:%.*]] = insertvalue { ptr, i32 } { ptr @g.resume.0, i32 undef }, i32 [[N]], 1
+; CHECK-NEXT:    ret { ptr, i32 } [[TMP2]]
+;
+entry:
+  %id = call token @llvm.coro.id.retcon(i32 1024, i32 8, i8* %buffer, i8* bitcast ({i8*, i32} (i8*, i1)* @prototype_g to i8*), i8* bitcast (i8* (i32)* @allocate to i8*), i8* bitcast (void (i8*)* @deallocate to i8*))
+  %hdl = call i8* @llvm.coro.begin(token %id, i8* null)
+  br label %loop
+
+loop:
+  %n.val = phi i32 [ %n, %entry ], [ %inc, %resume ]
+  %alloca = call token @llvm.coro.alloca.alloc.i32(i32 %n.val, i32 8)
+  %ptr = call i8* @llvm.coro.alloca.get(token %alloca)
+  call void @use(i8* %ptr)
+  call void @llvm.coro.alloca.free(token %alloca)
+  %unwind = call i1 (...) @llvm.coro.suspend.retcon.i1(i32 %n.val)
+  br i1 %unwind, label %cleanup, label %resume
+
+resume:
+  %inc = add i32 %n.val, 1
+  br label %loop
+
+cleanup:
+  call i1 @llvm.coro.end(i8* %hdl, i1 0)
+  unreachable
+}
+
+declare token @llvm.coro.id.retcon(i32, i32, i8*, i8*, i8*, i8*)
+declare i8* @llvm.coro.begin(token, i8*)
+declare i1 @llvm.coro.suspend.retcon.i1(...)
+declare void @llvm.coro.suspend.retcon.isVoid(...)
+declare i1 @llvm.coro.end(i8*, i1)
+declare i8* @llvm.coro.prepare.retcon(i8*)
+declare token @llvm.coro.alloca.alloc.i32(i32, i32)
+declare i8* @llvm.coro.alloca.get(token)
+declare void @llvm.coro.alloca.free(token)
+
+declare noalias i8* @allocate(i32 %size)
+declare void @deallocate(i8* %ptr)
+
+declare void @print(i32)
+declare void @use(i8*)