When dead code elimination removes all but one use, try to fold the single def into the remaining use.

Rematerialization can leave single-use loads behind that we might as well fold whenever possible.

llvm-svn: 128918

When DCE clones a live range because it separates into connected components,
make sure that the clones enter the same register allocator stage as the
register they were cloned from.

For instance, clones may be split even when they where created during spilling.
Other registers created during spilling are not candidates for splitting or even
(re-)spilling.

llvm-svn: 128524

The spill weight is not recomputed for an unspillable register - it stays infinite.

llvm-svn: 128490

llvm-svn: 128469

The instruction to be rematerialized may not be the one defining the register
that is being spilled. The traceSiblingValue() function sees through sibling
copies to find the remat candidate.

llvm-svn: 128449

The register allocator needs to know when the range shrinks.

llvm-svn: 128145

I have convinced myself that it can only happen when a phi value dies. When it
happens, allocate new virtual registers for the components.

llvm-svn: 127827

The register allocator needs to adjust its live interval unions when that happens.

llvm-svn: 127774

llvm-svn: 127773

llvm-svn: 127771

This allows the allocator to free any resources used by the virtual register,
including physical register assignments.

llvm-svn: 127560

This will we used for keeping register allocator data structures up to date
while LiveRangeEdit is trimming live intervals.

llvm-svn: 127300

LiveRangeEdit::eliminateDeadDefs() will eventually be used by coalescing,
splitting, and spilling for dead code elimination. It can delete chains of dead
instructions as long as there are no dependency loops.

llvm-svn: 127287

llvm-svn: 127181

llvm-svn: 126002

All new virtual registers created for spilling or splitting point back to their original.

llvm-svn: 125980

llvm-svn: 118661

give them individual stack slots once the are actually spilled.

llvm-svn: 117945

llvm-svn: 116962

llvm-svn: 116951

All registers created during splitting or spilling are assigned to the same
stack slot as the parent register.

When splitting or rematting, we may not spill at all. In that case the stack
slot is still assigned, but it will be dead.

llvm-svn: 116546

splitting or spillling, and to help with rematerialization.

Use LiveRangeEdit in InlineSpiller and SplitKit. This will eventually make it
possible to share remat code between InlineSpiller and SplitKit.

llvm-svn: 116543