Index: lib/Target/AMDGPU/AMDGPUISelLowering.h
===================================================================
--- lib/Target/AMDGPU/AMDGPUISelLowering.h
+++ lib/Target/AMDGPU/AMDGPUISelLowering.h
@@ -149,6 +149,9 @@
   SDValue LowerCall(CallLoweringInfo &CLI,
                     SmallVectorImpl<SDValue> &InVals) const override;
 
+  SDValue LowerDYNAMIC_STACKALLOC(SDValue Op,
+                                  SelectionDAG &DAG) const;
+
   SDValue LowerOperation(SDValue Op, SelectionDAG &DAG) const override;
   SDValue PerformDAGCombine(SDNode *N, DAGCombinerInfo &DCI) const override;
   void ReplaceNodeResults(SDNode * N,
Index: lib/Target/AMDGPU/AMDGPUISelLowering.cpp
===================================================================
--- lib/Target/AMDGPU/AMDGPUISelLowering.cpp
+++ lib/Target/AMDGPU/AMDGPUISelLowering.cpp
@@ -113,6 +113,9 @@
   setOperationAction(ISD::BR_JT, MVT::Other, Expand);
   setOperationAction(ISD::BRIND, MVT::Other, Expand);
 
+  // This is totally unsupported, just custom lower to produce an error.
+  setOperationAction(ISD::DYNAMIC_STACKALLOC, MVT::i32, Custom);
+
   // We need to custom lower some of the intrinsics
   setOperationAction(ISD::INTRINSIC_WO_CHAIN, MVT::Other, Custom);
 
@@ -613,6 +616,15 @@
   return SDValue();
 }
 
+SDValue AMDGPUTargetLowering::LowerDYNAMIC_STACKALLOC(SDValue Op,
+                                                      SelectionDAG &DAG) const {
+  const Function &Fn = *DAG.getMachineFunction().getFunction();
+
+  DiagnosticInfoUnsupported NoDynamicAlloca(Fn, "dynamic alloca");
+  DAG.getContext()->diagnose(NoDynamicAlloca);
+  return SDValue();
+}
+
 SDValue AMDGPUTargetLowering::LowerOperation(SDValue Op,
                                              SelectionDAG &DAG) const {
   switch (Op.getOpcode()) {
@@ -639,6 +651,7 @@
   case ISD::UINT_TO_FP: return LowerUINT_TO_FP(Op, DAG);
   case ISD::FP_TO_SINT: return LowerFP_TO_SINT(Op, DAG);
   case ISD::FP_TO_UINT: return LowerFP_TO_UINT(Op, DAG);
+  case ISD::DYNAMIC_STACKALLOC: return LowerDYNAMIC_STACKALLOC(Op, DAG);
   }
   return Op;
 }
Index: lib/Target/AMDGPU/AMDGPUPromoteAlloca.cpp
===================================================================
--- lib/Target/AMDGPU/AMDGPUPromoteAlloca.cpp
+++ lib/Target/AMDGPU/AMDGPUPromoteAlloca.cpp
@@ -276,6 +276,9 @@
 }
 
 void AMDGPUPromoteAlloca::visitAlloca(AllocaInst &I) {
+  if (!I.isStaticAlloca())
+    return;
+
   IRBuilder<> Builder(&I);
 
   // First try to replace the alloca with a vector
Index: test/CodeGen/AMDGPU/dynamic_stackalloc.ll
===================================================================
--- /dev/null
+++ test/CodeGen/AMDGPU/dynamic_stackalloc.ll
@@ -0,0 +1,11 @@
+; RUN: not llc -march=amdgcn -mcpu=tahiti -mattr=+promote-alloca -verify-machineinstrs < %s 2>&1 | FileCheck %s
+; RUN: not llc -march=amdgcn -mcpu=tahiti -mattr=-promote-alloca -verify-machineinstrs < %s 2>&1 | FileCheck %s
+; RUN: not llc -march=r600 -mcpu=cypress < %s 2>&1 | FileCheck %s
+
+; CHECK: error: unsupported dynamic alloca in test_dynamic_stackalloc
+
+define void @test_dynamic_stackalloc(i32 addrspace(1)* %out, i32 %n) {
+  %alloca = alloca i32, i32 %n
+  store volatile i32 0, i32* %alloca
+  ret void
+}