[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/AMDGPU/SIDebuggerInsertNops.cpp b/llvm/lib/Target/AMDGPU/SIDebuggerInsertNops.cpp
index 69ec381..c8ae8f7 100644
--- a/llvm/lib/Target/AMDGPU/SIDebuggerInsertNops.cpp
+++ b/llvm/lib/Target/AMDGPU/SIDebuggerInsertNops.cpp
@@ -78,8 +78,8 @@
 
   for (auto &MBB : MF) {
     for (auto MI = MBB.begin(); MI != MBB.end(); ++MI) {
-      // Skip DBG_VALUE instructions and instructions without location.
-      if (MI->isDebugValue() || !MI->getDebugLoc())
+      // Skip debug instructions and instructions without location.
+      if (MI->isDebugInstr() || !MI->getDebugLoc())
         continue;
 
       // Insert nop instruction if line number does not have nop inserted.