[AVX] Make Inits Foldable

Manage Inits in a FoldingSet.  This provides several benefits:

- Memory for Inits is properly managed

- Duplicate Inits are folded into Flyweights, saving memory

- It enforces const-correctness, protecting against certain classes
  of bugs

The above benefits allow Inits to be used in more contexts, which in
turn provides more dynamism to TableGen.  This enhanced capability
will be used by the AVX code generator to a fold common patterns
together.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@134907 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/utils/TableGen/CodeGenTarget.cpp b/utils/TableGen/CodeGenTarget.cpp
index 929791c..ceaa82f 100644
--- a/utils/TableGen/CodeGenTarget.cpp
+++ b/utils/TableGen/CodeGenTarget.cpp
@@ -402,7 +402,7 @@
 
   // Parse the list of return types.
   std::vector<MVT::SimpleValueType> OverloadedVTs;
-  ListInit *TypeList = R->getValueAsListInit("RetTypes");
+  const ListInit *TypeList = R->getValueAsListInit("RetTypes");
   for (unsigned i = 0, e = TypeList->getSize(); i != e; ++i) {
     Record *TyEl = TypeList->getElementAsRecord(i);
     assert(TyEl->isSubClassOf("LLVMType") && "Expected a type!");
@@ -470,7 +470,7 @@
   }
 
   // Parse the intrinsic properties.
-  ListInit *PropList = R->getValueAsListInit("Properties");
+  const ListInit *PropList = R->getValueAsListInit("Properties");
   for (unsigned i = 0, e = PropList->getSize(); i != e; ++i) {
     Record *Property = PropList->getElementAsRecord(i);
     assert(Property->isSubClassOf("IntrinsicProperty") &&