Fix issue in regscavenger when scavenging a callee-saved register that has not been spilled.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@77912 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 8 insertions, 1 deletions

diff --git a/lib/CodeGen/RegisterScavenging.cpp b/lib/CodeGen/RegisterScavenging.cpp
index e32d23264d..e1c8f2fe22 100644
--- a/lib/CodeGen/RegisterScavenging.cpp
+++ b/lib/CodeGen/RegisterScavenging.cpp
@@ -471,9 +471,16 @@ unsigned RegScavenger::scavengeRegister(const TargetRegisterClass *RC,
     Reg = Candidates.find_next(Reg);
   }
 
-  assert(ScavengedReg == 0 && 
+  assert(ScavengedReg == 0 &&
          "Scavenger slot is live, unable to scavenge another register!");
 
+  // Make sure SReg is marked as used. It could be considered available if it is
+  // one of the callee saved registers, but hasn't been spilled.
+  if (!isUsed(SReg)) {
+    MBB->addLiveIn(SReg);
+    setUsed(SReg);
+  }
+
   // Spill the scavenged register before I.
   TII->storeRegToStackSlot(*MBB, I, SReg, true, ScavengingFrameIndex, RC);
   MachineBasicBlock::iterator II = prior(I);