Index: llvm/trunk/lib/Target/AMDGPU/SIOptimizeExecMasking.cpp
===================================================================
--- llvm/trunk/lib/Target/AMDGPU/SIOptimizeExecMasking.cpp
+++ llvm/trunk/lib/Target/AMDGPU/SIOptimizeExecMasking.cpp
@@ -76,7 +76,7 @@
   case AMDGPU::COPY:
   case AMDGPU::S_MOV_B64: {
     const MachineOperand &Dst = MI.getOperand(0);
-    if (Dst.isReg() && Dst.getReg() == AMDGPU::EXEC)
+    if (Dst.isReg() && Dst.getReg() == AMDGPU::EXEC && MI.getOperand(1).isReg())
       return MI.getOperand(1).getReg();
     break;
   }
Index: llvm/trunk/test/CodeGen/AMDGPU/llvm.amdgcn.init.exec.ll
===================================================================
--- llvm/trunk/test/CodeGen/AMDGPU/llvm.amdgcn.init.exec.ll
+++ llvm/trunk/test/CodeGen/AMDGPU/llvm.amdgcn.init.exec.ll
@@ -74,6 +74,15 @@
   ret float %f
 }
 
+; GCN-LABEL: {{^}}init_unreachable:
+;
+; This used to crash.
+define amdgpu_ps void @init_unreachable() {
+main_body:
+  call void @llvm.amdgcn.init.exec(i64 -1)
+  unreachable
+}
+
 declare void @llvm.amdgcn.init.exec(i64) #1
 declare void @llvm.amdgcn.init.exec.from.input(i32, i32) #1