[LV][REFACTOR] One more tiny fix for printing debug locations in loop vectorizer. Now consistent with the remarks emitter.

[zinovy.nis]

Summary

I refactored a bit a code for printing loop locations in the loop vectorizer. Now the location is taken from loop itself, not from it's first instruction.

[echristo]

LGTM.

Thanks!

-eric

[nadav]

LGTM.

[zinovy.nis]

Closed by commit rL209197 (authored by @zinovy.nis).

llvm/trunk/lib/Transforms/Vectorize/LoopVectorize.cpp

 static void setDebugLocFromInst(IRBuilder<> &B, const Value *Ptr) {
   if (const Instruction *Inst = dyn_cast_or_null<Instruction>(Ptr))
     B.SetCurrentDebugLocation(Inst->getDebugLoc());
   else
     B.SetCurrentDebugLocation(DebugLoc());
 }
 
 #ifndef NDEBUG
-/// \return string containing a file name and a line # for the given
-/// instruction.
-static std::string getDebugLocString(const Instruction *I) {
+/// \return string containing a file name and a line # for the given loop.
+static std::string getDebugLocString(const Loop *L) {
   std::string Result;
-  if (I) {
+  if (L) {
     raw_string_ostream OS(Result);
-    const DebugLoc &InstrDebugLoc = I->getDebugLoc();
-    if (!InstrDebugLoc.isUnknown())
-      InstrDebugLoc.print(I->getContext(), OS);
+    const DebugLoc LoopDbgLoc = L->getStartLoc();
+    if (!LoopDbgLoc.isUnknown())
+      LoopDbgLoc.print(L->getHeader()->getContext(), OS);
     else
       // Just print the module name.
-      OS << I->getParent()->getParent()->getParent()->getModuleIdentifier();
+      OS << L->getHeader()->getParent()->getParent()->getModuleIdentifier();
     OS.flush();
   }
   return Result;
 }
 #endif
 
 /// LoopVectorizationLegality checks if it is legal to vectorize a loop, and
 /// to what vectorization factor.
bool runOnFunction(Function &F) override {
     // Process each loop nest in the function.
     return Changed;
   }
 
   bool processLoop(Loop *L) {
     assert(L->empty() && "Only process inner loops.");
 
 #ifndef NDEBUG
-    const std::string DebugLocStr =
-        getDebugLocString(L->getHeader()->getFirstNonPHIOrDbgOrLifetime());
+    const std::string DebugLocStr = getDebugLocString(L);
 #endif /* NDEBUG */
 
     DEBUG(dbgs() << "\nLV: Checking a loop in \""
                  << L->getHeader()->getParent()->getName() << "\" from "
                  << DebugLocStr << "\n");
 
     LoopVectorizeHints Hints(L, DisableUnrolling);