[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/MachineCSE.cpp b/llvm/lib/CodeGen/MachineCSE.cpp
index ce85034..75a3d07 100644
--- a/llvm/lib/CodeGen/MachineCSE.cpp
+++ b/llvm/lib/CodeGen/MachineCSE.cpp
@@ -314,7 +314,7 @@
   unsigned LookAheadLeft = LookAheadLimit;
   while (LookAheadLeft) {
     // Skip over dbg_value's.
-    while (I != E && I != EE && I->isDebugValue())
+    while (I != E && I != EE && I->isDebugInstr())
       ++I;
 
     if (I == EE) {
@@ -353,7 +353,7 @@
 
 bool MachineCSE::isCSECandidate(MachineInstr *MI) {
   if (MI->isPosition() || MI->isPHI() || MI->isImplicitDef() || MI->isKill() ||
-      MI->isInlineAsm() || MI->isDebugValue())
+      MI->isInlineAsm() || MI->isDebugInstr())
     return false;
 
   // Ignore copies.