The VTBL (and VTBX) instructions are rather permissive concerning the masks they

accept. If a value in the mask is out of range, it uses the value 0, for VTBL,
or leaves the value unchanged, for VTBX.

llvm-svn: 127700

1 files changed, 8 insertions, 0 deletions

diff --git a/llvm/lib/Target/ARM/ARMISelLowering.cpp b/llvm/lib/Target/ARM/ARMISelLowering.cpp
index 180b2c3b639..35a9bf78c2e 100644
--- a/llvm/lib/Target/ARM/ARMISelLowering.cpp
+++ b/llvm/lib/Target/ARM/ARMISelLowering.cpp
@@ -3541,6 +3541,13 @@ static bool isVREVMask(const SmallVectorImpl<int> &M, EVT VT,
   return true;
 }
 
+static bool isVTBLMask(const SmallVectorImpl<int> &M, EVT VT) {
+  // We can handle <8 x i8> vector shuffles. If the index in the mask is out of
+  // range, then 0 is placed into the resulting vector. So pretty much any mask
+  // of 8 elements can work here.
+  return VT == MVT::v8i8 && M.size() == 8;
+}
+
 static bool isVTRNMask(const SmallVectorImpl<int> &M, EVT VT,
                        unsigned &WhichResult) {
   unsigned EltSz = VT.getVectorElementType().getSizeInBits();
@@ -3980,6 +3987,7 @@ ARMTargetLowering::isShuffleMaskLegal(const SmallVectorImpl<int> &M,
           isVREVMask(M, VT, 32) ||
           isVREVMask(M, VT, 16) ||
           isVEXTMask(M, VT, ReverseVEXT, Imm) ||
+          isVTBLMask(M, VT) ||
           isVTRNMask(M, VT, WhichResult) ||
           isVUZPMask(M, VT, WhichResult) ||
           isVZIPMask(M, VT, WhichResult) ||