[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/CodeGen/LiveVariables.cpp b/llvm/lib/CodeGen/LiveVariables.cpp
index 87bb08a..0b92eab 100644
--- a/llvm/lib/CodeGen/LiveVariables.cpp
+++ b/llvm/lib/CodeGen/LiveVariables.cpp
@@ -499,7 +499,7 @@
 
 void LiveVariables::runOnInstr(MachineInstr &MI,
                                SmallVectorImpl<unsigned> &Defs) {
-  assert(!MI.isDebugValue());
+  assert(!MI.isDebugInstr());
   // Process all of the operands of the instruction...
   unsigned NumOperandsToProcess = MI.getNumOperands();
 
@@ -576,7 +576,7 @@
   DistanceMap.clear();
   unsigned Dist = 0;
   for (MachineInstr &MI : *MBB) {
-    if (MI.isDebugValue())
+    if (MI.isDebugInstr())
       continue;
     DistanceMap.insert(std::make_pair(&MI, Dist++));