+; CHECK-LABEL: imulq512:
+; CHECK: ## BB#0:
+; CHECK-NEXT: vpmuludq %zmm0, %zmm1, %zmm2
+; CHECK-NEXT: vpsrlq $32, %zmm0, %zmm3
+; CHECK-NEXT: vpmuludq %zmm3, %zmm1, %zmm3
+; CHECK-NEXT: vpsllq $32, %zmm3, %zmm3
+; CHECK-NEXT: vpaddq %zmm3, %zmm2, %zmm2
+; CHECK-NEXT: vpsrlq $32, %zmm1, %zmm1
+; CHECK-NEXT: vpmuludq %zmm0, %zmm1, %zmm0
+; CHECK-NEXT: vpsllq $32, %zmm0, %zmm0
+; CHECK-NEXT: vpaddq %zmm0, %zmm2, %zmm0
+; CHECK-NEXT: retq