interference check.

llvm-svn: 121519

llvm-svn: 121411

heuristic to reshuffle register assignments when we can't find an
available reg.

llvm-svn: 121388

llvm-svn: 121319

The hint is simply tried first and then forgotten if it couldn't be allocated
immediately.

llvm-svn: 121306

abstract priority queue interface in subclasses that want to override the
priority calculations.

Subclasses must provide a getPriority() implementation instead.

This approach requires less code as long as priorities are expressable as simple
floats, and it avoids the dangers of defining potentially expensive priority
comparison functions.

It also should speed up priority_queue operations since they no longer have to
chase pointers when comparing registers. This is not measurable, though.

Preferably, we shouldn't use floats to guide code generation. The use of floats
here is derived from the use of floats for spill weights. Spill weights have a
dynamic range that doesn't lend itself easily to a fixpoint implementation.

When someone invents a stable spill weight representation, it can be reused for
allocation priorities.

llvm-svn: 121294

llvm-svn: 121283

This new register allocator is initially identical to RegAllocBasic, but it will
receive all of the tricks that RegAllocBasic won't get.

RegAllocGreedy will eventually replace linear scan.

llvm-svn: 121234