Clean up static analyzer warnings.

Clang's static analyzer found several potential cases of undefined
behavior, use of un-initialized values, and potentially null pointer
dereferences in tablegen, Support, MC, and ADT. This cleans them up
with specific assertions on the assumptions of the code.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@224154 91177308-0d34-0410-b5e6-96231b3b80d8

utils/TableGen/CodeGenDAGPatterns.cpp

@@ -2569,8 +2569,10 @@ FindPatternInputsAndOutputs(TreePattern *I, TreePatternNode *Pat,
       I->error("set destination should be a register!");
 
     DefInit *Val = dyn_cast<DefInit>(Dest->getLeafValue());
-    if (!Val)
+    if (!Val) {
       I->error("set destination should be a register!");
+      continue;
+    }
 
     if (Val->getDef()->isSubClassOf("RegisterClass") ||
         Val->getDef()->isSubClassOf("ValueType") ||

utils/TableGen/CodeGenInstruction.cpp

@@ -537,7 +537,7 @@ bool CodeGenInstAlias::tryAliasOpMatch(DagInit *Result, unsigned AliasOpNo,
   // If both are Operands with the same MVT, allow the conversion. It's
   // up to the user to make sure the values are appropriate, just like
   // for isel Pat's.
-  if (InstOpRec->isSubClassOf("Operand") &&
+  if (InstOpRec->isSubClassOf("Operand") && ADI &&
       ADI->getDef()->isSubClassOf("Operand")) {
     // FIXME: What other attributes should we check here? Identical
     // MIOperandInfo perhaps?

utils/TableGen/CodeGenRegisters.cpp

@@ -146,6 +146,7 @@ void CodeGenRegister::buildObjectGraph(CodeGenRegBank &RegBank) {
 }
 
 const std::string &CodeGenRegister::getName() const {
+  assert(TheDef && "no def");
   return TheDef->getName();
 }