PR10998: It is not legal to sink an instruction past the terminator of a block; make sure we don't do that.

llvm-svn: 140428

1 files changed, 9 insertions, 1 deletions

diff --git a/llvm/lib/CodeGen/TwoAddressInstructionPass.cpp b/llvm/lib/CodeGen/TwoAddressInstructionPass.cpp
index dfd258d592e..d8793782228 100644
--- a/llvm/lib/CodeGen/TwoAddressInstructionPass.cpp
+++ b/llvm/lib/CodeGen/TwoAddressInstructionPass.cpp
@@ -177,6 +177,10 @@ char &llvm::TwoAddressInstructionPassID = TwoAddressInstructionPass::ID;
 bool TwoAddressInstructionPass::Sink3AddrInstruction(MachineBasicBlock *MBB,
                                            MachineInstr *MI, unsigned SavedReg,
                                            MachineBasicBlock::iterator OldPos) {
+  // FIXME: Shouldn't we be trying to do this before we three-addressify the
+  // instruction?  After this transformation is done, we no longer need
+  // the instruction to be in three-address form.
+
   // Check if it's safe to move this instruction.
   bool SeenStore = true; // Be conservative.
   if (!MI->isSafeToMove(TII, AA, SeenStore))
@@ -217,7 +221,11 @@ bool TwoAddressInstructionPass::Sink3AddrInstruction(MachineBasicBlock *MBB,
     break;
   }
 
-  if (!KillMI || KillMI->getParent() != MBB || KillMI == MI)
+  // If we find the instruction that kills SavedReg, and it is in an
+  // appropriate location, we can try to sink the current instruction
+  // past it.
+  if (!KillMI || KillMI->getParent() != MBB || KillMI == MI ||
+      KillMI->getDesc().isTerminator())
     return false;
 
   // If any of the definitions are used by another instruction between the