[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/BranchFolding.cpp b/llvm/lib/CodeGen/BranchFolding.cpp
index d1dd743..8db7113 100644
--- a/llvm/lib/CodeGen/BranchFolding.cpp
+++ b/llvm/lib/CodeGen/BranchFolding.cpp
@@ -358,7 +358,7 @@
   // I1==MBB1->begin() work as expected.)
   if (I1 == MBB1->begin() && I2 != MBB2->begin()) {
     --I2;
-    while (I2->isDebugValue()) {
+    while (I2->isDebugInstr()) {
       if (I2 == MBB2->begin())
         return TailLen;
       --I2;
@@ -367,7 +367,7 @@
   }
   if (I2 == MBB2->begin() && I1 != MBB1->begin()) {
     --I1;
-    while (I1->isDebugValue()) {
+    while (I1->isDebugInstr()) {
       if (I1 == MBB1->begin())
         return TailLen;
       --I1;
@@ -1499,7 +1499,7 @@
         // Check if DBG_VALUE at the end of PrevBB is identical to the
         // DBG_VALUE at the beginning of MBB.
         while (PrevBBIter != PrevBB.begin() && MBBIter != MBB->end()
-               && PrevBBIter->isDebugValue() && MBBIter->isDebugValue()) {
+               && PrevBBIter->isDebugInstr() && MBBIter->isDebugInstr()) {
           if (!MBBIter->isIdenticalTo(*PrevBBIter))
             break;
           MachineInstr &DuplicateDbg = *MBBIter;