[llvm] r293313 - NFC: Add debug tracing for more cases where loop unrolling fails.

[Anna Thomas via llvm-commits]

Author: annat
Date: Fri Jan 27 11:57:05 2017
New Revision: 293313

URL: http://llvm.org/viewvc/llvm-project?rev=293313&view=rev
Log:
NFC: Add debug tracing for more cases where loop unrolling fails.

Modified:
    llvm/trunk/lib/Transforms/Utils/LoopUnroll.cpp

Modified: llvm/trunk/lib/Transforms/Utils/LoopUnroll.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/LoopUnroll.cpp?rev=293313&r1=293312&r2=293313&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Utils/LoopUnroll.cpp (original)
+++ llvm/trunk/lib/Transforms/Utils/LoopUnroll.cpp Fri Jan 27 11:57:05 2017
@@ -306,8 +306,10 @@ bool llvm::UnrollLoop(Loop *L, unsigned
     Count = TripCount;
 
   // Don't enter the unroll code if there is nothing to do.
-  if (TripCount == 0 && Count < 2 && PeelCount == 0)
+  if (TripCount == 0 && Count < 2 && PeelCount == 0) {
+    DEBUG(dbgs() << "Won't unroll; almost nothing to do\n");
     return false;
+  }
 
   assert(Count > 0);
   assert(TripMultiple > 0);
@@ -362,8 +364,12 @@ bool llvm::UnrollLoop(Loop *L, unsigned
                                   PreserveLCSSA)) {
     if (Force)
       RuntimeTripCount = false;
-    else
+    else {
+      DEBUG(
+          dbgs() << "Wont unroll; prolog and epilog code could not be inserted "
+                    "when assuming runtime trip count\n");
       return false;
+    }
   }
 
   // Notify ScalarEvolution that the loop will be substantially changed,