[llvm] cddcc4c - A couple style tweaks on top of 5c0d1b2f9 [nfc]

[Philip Reames via llvm-commits]

Author: Philip Reames
Date: 2021-06-03T14:14:59-07:00
New Revision: cddcc4cff5052bc8a2311fea83f54b0caa1cbb4c

URL: https://github.com/llvm/llvm-project/commit/cddcc4cff5052bc8a2311fea83f54b0caa1cbb4c
DIFF: https://github.com/llvm/llvm-project/commit/cddcc4cff5052bc8a2311fea83f54b0caa1cbb4c.diff

LOG: A couple style tweaks on top of 5c0d1b2f9 [nfc]

Added: 
    

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

Removed: 
    


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diff  --git a/llvm/lib/Transforms/Utils/LoopUnroll.cpp b/llvm/lib/Transforms/Utils/LoopUnroll.cpp
index fa0a51424a8a..76036dc2234a 100644
--- a/llvm/lib/Transforms/Utils/LoopUnroll.cpp
+++ b/llvm/lib/Transforms/Utils/LoopUnroll.cpp
@@ -411,6 +411,10 @@ LoopUnrollResult llvm::UnrollLoop(Loop *L, UnrollLoopOptions ULO, LoopInfo *LI,
       dbgs() << "  No single exiting block\n";
   });
 
+  // Warning: ExactTripCount is the exact trip count for the block ending in
+  // ExitingBI, not neccessarily an exact exit count *for the loop*.  The
+  // distinction comes when we have an exiting latch, but the loop exits
+  // through another exit first.
   const unsigned ExactTripCount = ExitingBI ?
     SE->getSmallConstantTripCount(L,ExitingBI->getParent()) : 0;
   const bool ExactUnroll = (ExactTripCount && ExactTripCount == ULO.Count);
@@ -762,13 +766,13 @@ LoopUnrollResult llvm::UnrollLoop(Loop *L, UnrollLoopOptions ULO, LoopInfo *LI,
             return None;
           return j == 0;
         }
-        if (ExactUnroll)
-          return j == 0;
-        // Full, but non-exact unrolling
+        // Complete (but possibly inexact) unrolling
         if (j == 0)
           return true;
         if (MaxTripCount && j >= MaxTripCount)
           return false;
+        // Warning: ExactTripCount is the trip count of the exiting
+        // block which ends in ExitingBI, not neccessarily the loop.
         if (ExactTripCount && j != ExactTripCount)
           return false;
         return None;