Index: docs/LangRef.rst
===================================================================
--- docs/LangRef.rst
+++ docs/LangRef.rst
@@ -1602,6 +1602,14 @@
 Similarly, if no funclet EH pads have been entered-but-not-yet-exited,
 executing a ``call`` or ``invoke`` with a ``"funclet"`` bundle is undefined behavior.
 
+GC Transition Operand Bundles
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+GC transition operand bundles are characterized by the
+``"gc-transition"`` operand bundle tag.
+
+TODO
+
 .. _moduleasm:
 
 Module-Level Inline Assembly
Index: include/llvm/IR/LLVMContext.h
===================================================================
--- include/llvm/IR/LLVMContext.h
+++ include/llvm/IR/LLVMContext.h
@@ -71,8 +71,9 @@
   /// Additionally, this scheme allows LLVM to efficiently check for specific
   /// operand bundle tags without comparing strings.
   enum {
-    OB_deopt = 0,   // "deopt"
-    OB_funclet = 1, // "funclet"
+    OB_deopt = 0,         // "deopt"
+    OB_funclet = 1,       // "funclet"
+    OB_gc_transition = 2, // "gc-transition"
   };
 
   /// getMDKindID - Return a unique non-zero ID for the specified metadata kind.
Index: lib/IR/LLVMContext.cpp
===================================================================
--- lib/IR/LLVMContext.cpp
+++ lib/IR/LLVMContext.cpp
@@ -137,6 +137,11 @@
   assert(FuncletEntry->second == LLVMContext::OB_funclet &&
          "funclet operand bundle id drifted!");
   (void)FuncletEntry;
+
+  auto *GCTransitionEntry = pImpl->getOrInsertBundleTag("gc-transition");
+  assert(GCTransitionEntry->second == LLVMContext::OB_gc_transition &&
+         "gc-transition operand bundle id drifted!");
+  (void)GCTransitionEntry;
 }
 LLVMContext::~LLVMContext() { delete pImpl; }
 
Index: lib/IR/Verifier.cpp
===================================================================
--- lib/IR/Verifier.cpp
+++ lib/IR/Verifier.cpp
@@ -2514,7 +2514,8 @@
 
   // Verify that a callsite has at most one "deopt" and one "funclet" operand
   // bundle.
-  bool FoundDeoptBundle = false, FoundFuncletBundle = false;
+  bool FoundDeoptBundle = false, FoundFuncletBundle = false,
+       FoundGCTransitionBundle = false;
   for (unsigned i = 0, e = CS.getNumOperandBundles(); i < e; ++i) {
     OperandBundleUse BU = CS.getOperandBundleAt(i);
     uint32_t Tag = BU.getTagID();
@@ -2522,6 +2523,11 @@
       Assert(!FoundDeoptBundle, "Multiple deopt operand bundles", I);
       FoundDeoptBundle = true;
     }
+    if (Tag == LLVMContext::OB_gc_transition) {
+      Assert(!FoundGCTransitionBundle, "Multiple gc-transition operand bundles",
+             I);
+      FoundGCTransitionBundle = true;
+    }
     if (Tag == LLVMContext::OB_funclet) {
       Assert(!FoundFuncletBundle, "Multiple funclet operand bundles", I);
       FoundFuncletBundle = true;
Index: lib/Transforms/Scalar/RewriteStatepointsForGC.cpp
===================================================================
--- lib/Transforms/Scalar/RewriteStatepointsForGC.cpp
+++ lib/Transforms/Scalar/RewriteStatepointsForGC.cpp
@@ -1404,8 +1404,11 @@
   if (UseDeoptBundles) {
     CallArgs = {CS.arg_begin(), CS.arg_end()};
     DeoptArgs = GetDeoptBundleOperands(CS);
-    // TODO: we don't fill in TransitionArgs or Flags in this branch, but we
-    // could have an operand bundle for that too.
+    if (auto TransitionBundle =
+            CS.getOperandBundle(LLVMContext::OB_gc_transition)) {
+      Flags |= uint32_t(StatepointFlags::GCTransition);
+      TransitionArgs = TransitionBundle->Inputs;
+    }
     AttributeSet OriginalAttrs = CS.getAttributes();
 
     Attribute AttrID = OriginalAttrs.getAttribute(AttributeSet::FunctionIndex,
Index: test/Transforms/RewriteStatepointsForGC/deopt-bundles/basic.ll
===================================================================
--- test/Transforms/RewriteStatepointsForGC/deopt-bundles/basic.ll
+++ test/Transforms/RewriteStatepointsForGC/deopt-bundles/basic.ll
@@ -63,3 +63,11 @@
   %lpad = landingpad token cleanup
   resume token undef
 }
+
+define i32 addrspace(1)* @f4(i32 addrspace(1)* %arg) gc "statepoint-example" {
+; CHECK-LABEL: @f4(
+ entry:
+; CHECK: @llvm.experimental.gc.statepoint.p0f_isVoidf(i64 2882400000, i32 0, void ()* @g, i32 0, i32 1, i32 2, i32 400, i8 90,
+  call void @g() [ "gc-transition"(i32 400, i8 90) ]
+  ret i32 addrspace(1)* %arg
+}
Index: test/Verifier/operand-bundles.ll
===================================================================
--- test/Verifier/operand-bundles.ll
+++ test/Verifier/operand-bundles.ll
@@ -47,3 +47,16 @@
   %x = add i32 42, 1
   ret void
 }
+
+define void @f_gc_transition(i32* %ptr) {
+; CHECK: Multiple gc-transition operand bundles
+; CHECK-NEXT: call void @g() [ "gc-transition"(i32 42, i64 100, i32 %x), "gc-transition"(float 0.000000e+00, i64 100, i32 %l) ]
+; CHECK-NOT: call void @g() [ "gc-transition"(i32 42, i64 120, i32 %x) ]
+
+ entry:
+  %l = load i32, i32* %ptr
+  call void @g() [ "gc-transition"(i32 42, i64 100, i32 %x), "gc-transition"(float 0.0, i64 100, i32 %l) ]
+  call void @g() [ "gc-transition"(i32 42, i64 120) ]  ;; The verifier should not complain about this one
+  %x = add i32 42, 1
+  ret void
+}