[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.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@331844 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/StackSlotColoring.cpp

@@ -423,7 +423,7 @@ bool StackSlotColoring::RemoveDeadStores(MachineBasicBlock* MBB) {
     if (!(LoadReg = TII->isLoadFromStackSlot(*I, FirstSS, LoadSize)))
       continue;
     // Skip the ...pseudo debugging... instructions between a load and store.
-    while ((NextMI != E) && NextMI->isDebugValue()) {
+    while ((NextMI != E) && NextMI->isDebugInstr()) {
       ++NextMI;
       ++I;
     }