Jakob Stoklund Olesen ebac0c1747 Spill mode: Hoist back-copies locally.
The leaveIntvAfter() function normally inserts a back-copy after the
requested instruction, making the back-copy kill the live range.

In spill mode, try to insert the back-copy before the last use instead.
That means the last use becomes the kill instead of the back-copy.  This
lowers the register pressure because the last use can now redefine the
same register it was reading.

This will also improve compile time: The back-copy isn't a kill, so
hoisting it in hoistCopiesForSize() won't force a recomputation of the
source live range.  Similarly, if the back-copy isn't hoisted by the
splitter, the spiller will not attempt hoisting it locally.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@139883 91177308-0d34-0410-b5e6-96231b3b80d8
2011-09-16 00:03:35 +00:00
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2011-09-15 23:45:50 +00:00
2011-09-13 19:42:23 +00:00
2011-09-13 19:42:23 +00:00