From 7b3392326c40c3c20697816acae597ba7b3144eb Mon Sep 17 00:00:00 2001
From: dim <dim@FreeBSD.org>
Date: Thu, 20 Oct 2011 21:10:27 +0000
Subject: Vendor import of llvm release_30 branch r142614:
 http://llvm.org/svn/llvm-project/llvm/branches/release_30@142614

---
 lib/CodeGen/MachineCSE.cpp | 11 +++++++++++
 1 file changed, 11 insertions(+)

(limited to 'lib/CodeGen/MachineCSE.cpp')

diff --git a/lib/CodeGen/MachineCSE.cpp b/lib/CodeGen/MachineCSE.cpp
index 3a60a37..7eda8c1 100644
--- a/lib/CodeGen/MachineCSE.cpp
+++ b/lib/CodeGen/MachineCSE.cpp
@@ -430,13 +430,24 @@ bool MachineCSE::ProcessBlock(MachineBasicBlock *MBB) {
       unsigned NewReg = CSMI->getOperand(i).getReg();
       if (OldReg == NewReg)
         continue;
+
       assert(TargetRegisterInfo::isVirtualRegister(OldReg) &&
              TargetRegisterInfo::isVirtualRegister(NewReg) &&
              "Do not CSE physical register defs!");
+
       if (!isProfitableToCSE(NewReg, OldReg, CSMI, MI)) {
         DoCSE = false;
         break;
       }
+
+      // Don't perform CSE if the result of the old instruction cannot exist
+      // within the register class of the new instruction.
+      const TargetRegisterClass *OldRC = MRI->getRegClass(OldReg);
+      if (!MRI->constrainRegClass(NewReg, OldRC)) {
+        DoCSE = false;
+        break;
+      }
+
       CSEPairs.push_back(std::make_pair(OldReg, NewReg));
       --NumDefs;
     }
-- 
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