From cc07e04262fe4bc35469fbadc53d2ec7bfd02fe2 Mon Sep 17 00:00:00 2001 From: Jakob Stoklund Olesen Date: Thu, 28 Jul 2011 20:48:23 +0000 Subject: Reverse order of RS_Split live ranges under -compact-regions. There are two conflicting strategies in play: - Under high register pressure, we want to assign large live ranges first. Smaller live ranges are easier to place afterwards. - Live range splitting is guided by interference, so splitting should be deferred until interference is as realistic as possible. With the recent changes to the live range stages, and with compact regions enabled, it is less traumatic to split a live range too early. If some of the split products were too big, they can often be split again. By reversing the RS_Split order, we get this queue order: 1. Normal live ranges, large to small. 2. RS_Split live ranges, large to small. The large-to-small order improves RAGreedy's puzzle solving skills under high register pressure. It may cause a bit more iterated splitting, but we handle that better now. With this change, -compact-regions is mostly an improvement on SPEC. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@136388 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/CodeGen/RegAllocGreedy.cpp | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) (limited to 'lib/CodeGen/RegAllocGreedy.cpp') diff --git a/lib/CodeGen/RegAllocGreedy.cpp b/lib/CodeGen/RegAllocGreedy.cpp index 1f0c241dd2..239c8e4359 100644 --- a/lib/CodeGen/RegAllocGreedy.cpp +++ b/lib/CodeGen/RegAllocGreedy.cpp @@ -398,12 +398,15 @@ void RAGreedy::enqueue(LiveInterval *LI) { if (ExtraRegInfo[Reg].Stage == RS_New) ExtraRegInfo[Reg].Stage = RS_Assign; - if (ExtraRegInfo[Reg].Stage == RS_Split) + if (ExtraRegInfo[Reg].Stage == RS_Split) { // Unsplit ranges that couldn't be allocated immediately are deferred until // everything else has been allocated. Long ranges are allocated last so // they are split against realistic interference. - Prio = (1u << 31) - Size; - else { + if (CompactRegions) + Prio = Size; + else + Prio = (1u << 31) - Size; + } else { // Everything else is allocated in long->short order. Long ranges that don't // fit should be spilled ASAP so they don't create interference. Prio = (1u << 31) + Size; -- cgit v1.2.3-18-g5258