From 60a26a6578e2cca3c1092b14c3615979d12e3eab Mon Sep 17 00:00:00 2001
From: Jakob Stoklund Olesen <stoklund@2pi.dk>
Date: Mon, 21 Feb 2011 23:09:46 +0000
Subject: Add SplitKit::isOriginalEndpoint and use it to force live range
 splitting to terminate.

An original endpoint is an instruction that killed or defined the original live
range before any live ranges were split.

When splitting global live ranges, avoid creating local live ranges without any
original endpoints. We may still create global live ranges without original
endpoints, but such a range won't be split again, and live range splitting still
terminates.

llvm-svn: 126151
---
 llvm/lib/CodeGen/SplitKit.cpp | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

(limited to 'llvm/lib/CodeGen/SplitKit.cpp')

diff --git a/llvm/lib/CodeGen/SplitKit.cpp b/llvm/lib/CodeGen/SplitKit.cpp
index 5663936bf3a..a97d890c25b 100644
--- a/llvm/lib/CodeGen/SplitKit.cpp
+++ b/llvm/lib/CodeGen/SplitKit.cpp
@@ -167,6 +167,20 @@ void SplitAnalysis::calcLiveBlockInfo() {
   }
 }
 
+bool SplitAnalysis::isOriginalEndpoint(SlotIndex Idx) const {
+  unsigned OrigReg = VRM.getOriginal(CurLI->reg);
+  const LiveInterval &Orig = LIS.getInterval(OrigReg);
+  assert(!Orig.empty() && "Splitting empty interval?");
+  LiveInterval::const_iterator I = Orig.find(Idx);
+
+  // Range containing Idx should begin at Idx.
+  if (I != Orig.end() && I->start <= Idx)
+    return I->start == Idx;
+
+  // Range does not contain Idx, previous must end at Idx.
+  return I != Orig.begin() && (--I)->end == Idx;
+}
+
 void SplitAnalysis::print(const BlockPtrSet &B, raw_ostream &OS) const {
   for (BlockPtrSet::const_iterator I = B.begin(), E = B.end(); I != E; ++I) {
     unsigned count = UsingBlocks.lookup(*I);
-- 
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