[DebugInfo] Examine all uses of isDebugValue() for debug instructions.

Because we create a new kind of debug instruction, DBG_LABEL, we need to
check all passes which use isDebugValue() to check MachineInstr is debug
instruction or not. When expelling debug instructions, we should expel
both DBG_VALUE and DBG_LABEL. So, I create a new function,
isDebugInstr(), in MachineInstr to check whether the MachineInstr is
debug instruction or not.

This patch has no new test case. I have run regression test and there is
no difference in regression test.

Differential Revision: https://reviews.llvm.org/D45342

Patch by Hsiangkai Wang.

llvm-svn: 331844
diff --git a/llvm/lib/Target/Hexagon/HexagonSplitDouble.cpp b/llvm/lib/Target/Hexagon/HexagonSplitDouble.cpp
index 4979ce1..386e6cb 100644
--- a/llvm/lib/Target/Hexagon/HexagonSplitDouble.cpp
+++ b/llvm/lib/Target/Hexagon/HexagonSplitDouble.cpp
@@ -163,7 +163,7 @@
   if (MI->mayLoad() || MI->mayStore())
     if (MemRefsFixed || isVolatileInstr(MI))
       return true;
-  if (MI->isDebugValue())
+  if (MI->isDebugInstr())
     return false;
 
   unsigned Opc = MI->getOpcode();