[AArch64][GlobalISel] Guard against no operands in matchHoistLogicOpWithSameOpcodeHands

In case both LeftHandInst and RightHandInst are IMPLICIT_DEF with no input
operands, this patch protects against the post-legalizer-combiner
matchHoistLogicOpWithSameOpcodeHands with no operands. The
prelegalizercombiner-hoist-same-hands.mir test was cleaned up a little in the
process, and has a post-legalizer run line added so that the implicit_def do
not get folded awwy.

Author: davemgreen

llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp

@@ -3095,7 +3095,9 @@ bool CombinerHelper::matchHoistLogicOpWithSameOpcodeHands(
   unsigned HandOpcode = LeftHandInst->getOpcode();
   if (HandOpcode != RightHandInst->getOpcode())
     return false;
-  if (!LeftHandInst->getOperand(1).isReg() ||
+  if (LeftHandInst->getNumOperands() < 2 ||
+      !LeftHandInst->getOperand(1).isReg() ||
+      RightHandInst->getNumOperands() < 2 ||
       !RightHandInst->getOperand(1).isReg())
     return false;