[PATCH] [AArch64] Enhance rematerialization by adding a new API isAsCheapAsAMove in TargetInstroInfo

[Tim Northover]

Just one comment on Quentin's comments:

================
Comment at: lib/Target/AArch64/AArch64InstrFormats.td:1615
@@ -1614,3 +1614,3 @@
                   SDPatternOperator OpNode = null_frag> {
-  let hasSideEffects = 0 in {
+  let hasSideEffects = 0, isReMaterializable = 1 in {
   // Add/Subtract immediate
----------------
Quentin Colombet wrote:
> Since we are overriding the behavior of isAsCheapAsMove, I think it would make sense to set the isAsCheapAsMove flag as well as the isRematerializable flag.
> 
> What do you think?
> 
> Also, we may want to check the uses of isAsCheapAsMove to see if we should "promote" them to the new target hook.
Careful if you do that, I don't think it is as cheap as a move on Cyclone.

http://reviews.llvm.org/D4361