[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/AVR/AVRInstrInfo.cpp b/llvm/lib/Target/AVR/AVRInstrInfo.cpp
index 1a89a13..0c32334 100644
--- a/llvm/lib/Target/AVR/AVRInstrInfo.cpp
+++ b/llvm/lib/Target/AVR/AVRInstrInfo.cpp
@@ -273,7 +273,7 @@
 
   while (I != MBB.begin()) {
     --I;
-    if (I->isDebugValue()) {
+    if (I->isDebugInstr()) {
       continue;
     }
 
@@ -444,7 +444,7 @@
 
   while (I != MBB.begin()) {
     --I;
-    if (I->isDebugValue()) {
+    if (I->isDebugInstr()) {
       continue;
     }
     //:TODO: add here the missing jmp instructions once they are implemented