[ARM][ParallelDSP] Disable for big-endian

Bail early when we don't have a preheader and also if the target is
big endian because it's written with only little endian in mind!

Differential Revision: https://reviews.llvm.org/D59368

llvm-svn: 356243
diff --git a/llvm/test/CodeGen/ARM/ParallelDSP/multi-use-loads.ll b/llvm/test/CodeGen/ARM/ParallelDSP/multi-use-loads.ll
index 21d43b0..524424a 100644
--- a/llvm/test/CodeGen/ARM/ParallelDSP/multi-use-loads.ll
+++ b/llvm/test/CodeGen/ARM/ParallelDSP/multi-use-loads.ll
@@ -1,4 +1,7 @@
 ; RUN: llc -O3 -mtriple=arm-arm-eabi -mcpu=cortex-m33 < %s | FileCheck %s
+; RUN: llc -O3 -mtriple=armeb-arm-eabi -mcpu=cortex-m33 < %s | FileCheck %s --check-prefix=CHECK-UNSUPPORTED
+
+; CHECK-UNSUPPORTED-NOT: smlad
 
 ; CHECK-LABEL: add_user
 ; CHECK: %for.body