Fixed register allocator splitting a live range on a spilling variable.

If we create new intervals for a variable that is being spilled, then those new intervals are not guaranteed to also spill.  This means that anything reading from the original spilling value might not get the correct value if spills were missed.

Fixes <rdar://problem/10546864>

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@146428 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 17 insertions, 1 deletions

diff --git a/lib/CodeGen/LiveRangeEdit.cpp b/lib/CodeGen/LiveRangeEdit.cpp
index 428b252f97..a470877e12 100644
--- a/lib/CodeGen/LiveRangeEdit.cpp
+++ b/lib/CodeGen/LiveRangeEdit.cpp
@@ -210,7 +210,8 @@ bool LiveRangeEdit::foldAsLoad(LiveInterval *LI,
 
 void LiveRangeEdit::eliminateDeadDefs(SmallVectorImpl<MachineInstr*> &Dead,
                                       LiveIntervals &LIS, VirtRegMap &VRM,
-                                      const TargetInstrInfo &TII) {
+                                      const TargetInstrInfo &TII,
+                                      ArrayRef<unsigned> RegsBeingSpilled) {
   SetVector<LiveInterval*,
             SmallVector<LiveInterval*, 8>,
             SmallPtrSet<LiveInterval*, 8> > ToShrink;
@@ -290,6 +291,21 @@ void LiveRangeEdit::eliminateDeadDefs(SmallVectorImpl<MachineInstr*> &Dead,
       delegate_->LRE_WillShrinkVirtReg(LI->reg);
     if (!LIS.shrinkToUses(LI, &Dead))
       continue;
+    
+    // Don't create new intervals for a register being spilled.
+    // The new intervals would have to be spilled anyway so its not worth it.
+    // Also they currently aren't spilled so creating them and not spilling
+    // them results in incorrect code.
+    bool BeingSpilled = false;
+    for (unsigned i = 0, e = RegsBeingSpilled.size(); i != e; ++i) {
+      if (LI->reg == RegsBeingSpilled[i]) {
+        BeingSpilled = true;
+        break;
+      }
+    }
+    
+    if (BeingSpilled) continue;
+    
 
     // LI may have been separated, create new intervals.
     LI->RenumberValues(LIS);