Avoid comparing invalid slot indexes, and assert that it doesn't happen.

The SlotIndex created by the default construction does not represent a position
in the function, and it doesn't make sense to compare it to other indexes.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@126924 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 2 insertions, 1 deletions

diff --git a/include/llvm/CodeGen/SlotIndexes.h b/include/llvm/CodeGen/SlotIndexes.h
index 8d3b1c0933..153e520a47 100644
--- a/include/llvm/CodeGen/SlotIndexes.h
+++ b/include/llvm/CodeGen/SlotIndexes.h
@@ -135,6 +135,7 @@ namespace llvm {
     }
 
     IndexListEntry& entry() const {
+      assert(isValid() && "Attempt to compare reserved index.");
       return *lie.getPointer();
     }
 
@@ -530,7 +531,7 @@ namespace llvm {
     /// Returns the instruction for the given index, or null if the given
     /// index has no instruction associated with it.
     MachineInstr* getInstructionFromIndex(SlotIndex index) const {
-      return index.entry().getInstr();
+      return index.isValid() ? index.entry().getInstr() : 0;
     }
 
     /// Returns the next non-null index.