X86: Properly decode shuffle masks when the constant pool type is weird

It's possible for the constant pool entry for the shuffle mask to come
from a completely different operation.  This occurs when Constants have
the same bit pattern but have different types.

Make DecodePSHUFBMask tolerant of types which, after a bitcast, are
appropriately sized vector types.

This fixes PR22188.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@225597 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Target/X86/X86MCInstLower.cpp

@@ -1161,7 +1161,7 @@ void X86AsmPrinter::EmitInstruction(const MachineInstr *MI) {
 
     if (auto *C = getConstantFromPool(*MI, MaskOp)) {
       SmallVector<int, 16> Mask;
-      DecodePSHUFBMask(C, Mask);
+      DecodePSHUFBMask(C, TM.getSubtargetImpl()->getDataLayout(), Mask);
       if (!Mask.empty())
         OutStreamer.AddComment(getShuffleComment(DstOp, SrcOp, Mask));
     }