framework. It's purpose is not to improve register allocation per se,
but to make it easier to develop powerful live range splitting. I call
it the basic allocator because it is as simple as a global allocator
can be but provides the building blocks for sophisticated register
allocation with live range splitting. 

A minimal implementation is provided that trivially spills whenever it
runs out of registers. I'm checking in now to get high-level design
and style feedback. I've only done minimal testing. The next step is
implementing a "greedy" allocation algorithm that does some register
reassignment and makes better splitting decisions.

llvm-svn: 117174

llvm-svn: 117173

llvm-svn: 117172

llvm-svn: 117171

llvm-svn: 117170

When a block has exactly two uses and the register is both live-in and live-out,
don't isolate the block. We would be inserting two copies, so we haven't really
made any progress.

If the live-in and live-out values separate into disconnected components after
splitting, we would be making progress. We can't detect that for now.

llvm-svn: 117169

llvm-svn: 117166

llvm-svn: 117165

Apple builds.  Radar 8585383.

llvm-svn: 117164

llvm-svn: 117158

llvm-svn: 117157

llvm-svn: 117156

llvm-svn: 117155

llvm-svn: 117154

llvm-svn: 117151

llvm-svn: 117145

An exit block with a critical edge must only have predecessors in the loop, or
just before the loop. This guarantees that the inserted copies in the loop
predecessors dominate the exit block.

llvm-svn: 117144

llvm-svn: 117143

llvm-svn: 117134

llvm-svn: 117133

llvm-svn: 117132

llvm-svn: 117131

llvm-svn: 117130

llvm-svn: 117128

llvm-svn: 117126

llvm-svn: 117124

llvm-svn: 117122

llvm-svn: 117121

llvm-svn: 117119

llvm-svn: 117115

definitions.

llvm-svn: 117114

Patch by Frits van Bommel!

llvm-svn: 117113

llvm-svn: 117111

See PR 8473.

llvm-svn: 117109

llvm-svn: 117108

actually changed.

Patch by Frits van Bommel!

llvm-svn: 117102

llvm-svn: 117099

llvm-svn: 117095

test equality to 1, and fix/update documentation to reflect this

llvm-svn: 117094

lit -jN causes crash on Cygwin's python.

llvm-svn: 117093