Mark all uses as <undef> when joining a copy.

This way, shrinkToUses() will ignore the instruction that is about to be
deleted, and we avoid leaving invalid live ranges that SplitKit doesn't like.

Fix a misunderstanding in MachineVerifier about <def,undef> operands. The
<undef> flag is valid on def operands where it has the same meaning as <undef>
on a use operand. It only applies to sub-register defines which also read the
full register.

llvm-svn: 128642

1 files changed, 3 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/SimpleRegisterCoalescing.h b/llvm/lib/CodeGen/SimpleRegisterCoalescing.h
index 11849dfca05..6e79a40c8b2 100644
--- a/llvm/lib/CodeGen/SimpleRegisterCoalescing.h
+++ b/llvm/lib/CodeGen/SimpleRegisterCoalescing.h
@@ -176,6 +176,9 @@ namespace llvm {
     /// cycles Start and End or NULL if there are no uses.
     MachineOperand *lastRegisterUse(SlotIndex Start, SlotIndex End,
                                     unsigned Reg, SlotIndex &LastUseIdx) const;
+
+    /// markAsJoined - Remember that CopyMI has already been joined.
+    void markAsJoined(MachineInstr *CopyMI);
   };
 
 } // End llvm namespace