[PowerPC] Enable printing instructions using aliases

TableGen had been nicely generating code to print a number of instructions using
shorter aliases (and PowerPC has plenty of short mnemonics), but we were not
calling it. For some of the aliases we support in the parser, TableGen can't
infer the "inverse" alias relationship, so there is still more to do.

Thus, after some hours of updating test cases...

llvm-svn: 235616
diff --git a/llvm/lib/Target/PowerPC/InstPrinter/PPCInstPrinter.cpp b/llvm/lib/Target/PowerPC/InstPrinter/PPCInstPrinter.cpp
index 1576544..046682d 100644
--- a/llvm/lib/Target/PowerPC/InstPrinter/PPCInstPrinter.cpp
+++ b/llvm/lib/Target/PowerPC/InstPrinter/PPCInstPrinter.cpp
@@ -31,6 +31,7 @@
 FullRegNames("ppc-asm-full-reg-names", cl::Hidden, cl::init(false),
              cl::desc("Use full register names when printing assembly"));
 
+#define PRINT_ALIAS_INSTR
 #include "PPCGenAsmWriter.inc"
 
 void PPCInstPrinter::printRegName(raw_ostream &OS, unsigned RegNo) const {
@@ -111,8 +112,9 @@
   // precision).  FIXME: Is there a better solution?
   if (MI->getOpcode() == TargetOpcode::COPY_TO_REGCLASS)
     return;
-  
-  printInstruction(MI, O);
+
+  if (!printAliasInstr(MI, O))
+    printInstruction(MI, O);
   printAnnotation(O, Annot);
 }