Lazily defer duplicating the live interval we are splitting until we know it is

necessary.

Sometimes, live range splitting doesn't shrink the current interval, but simply
changes some instructions to use a new interval. That makes the original more
suitable for spilling. In this case, we don't need to duplicate the original.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@110481 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 4 insertions, 3 deletions

diff --git a/lib/CodeGen/InlineSpiller.cpp b/lib/CodeGen/InlineSpiller.cpp
index 1492566cfe..5ac66105d8 100644
--- a/lib/CodeGen/InlineSpiller.cpp
+++ b/lib/CodeGen/InlineSpiller.cpp
@@ -113,9 +113,10 @@ bool InlineSpiller::split() {
   splitAnalysis_.analyze(li_);
 
   if (const MachineLoop *loop = splitAnalysis_.getBestSplitLoop()) {
-    SplitEditor(splitAnalysis_, lis_, vrm_, *newIntervals_)
-      .splitAroundLoop(loop);
-    return true;
+    // We can split, but li_ may be left intact with fewer uses.
+    if (SplitEditor(splitAnalysis_, lis_, vrm_, *newIntervals_)
+          .splitAroundLoop(loop))
+      return true;
   }
   return false;
 }