Update the tag for Init to match how it's defined.

llvm-svn: 134908

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.

llvm-svn: 134907

llvm-svn: 132636

llvm-svn: 132624

A TableGen backend can define how certain classes can be expanded into
ordered sets of defs, typically by evaluating a specific field in the
record. The SetTheory class can then evaluate DAG expressions that refer
to these named sets.

A number of standard set and list operations are predefined, and the
backend can add more specialized operators if needed. The -print-sets
backend is used by SetTheory.td to provide examples.

This is intended to simplify how register classes are defined:

  def GR32_NOSP : RegisterClass<"X86", [i32], 32, (sub GR32, ESP)>;

llvm-svn: 132621