Revert "[LoopUnroll] Use the upper bound of the loop trip count to fullly unroll a loop"

This reverts commit r284044.

llvm-svn: 284051

1 files changed, 9 insertions, 18 deletions

diff --git a/llvm/lib/Transforms/Utils/LoopUnroll.cpp b/llvm/lib/Transforms/Utils/LoopUnroll.cpp
index 847224753f4..77b744ec881 100644
--- a/llvm/lib/Transforms/Utils/LoopUnroll.cpp
+++ b/llvm/lib/Transforms/Utils/LoopUnroll.cpp
@@ -187,10 +187,6 @@ static bool needToInsertPhisForLCSSA(Loop *L, std::vector<BasicBlock *> Blocks,
 /// iterations via an early branch, but control may not exit the loop from the
 /// LatchBlock's terminator prior to TripCount iterations.
 ///
-/// PreserveCondBr indicates whether the conditional branch of the LatchBlock
-/// needs to be preserved.  It is needed when we use trip count upper bound to
-/// fully unroll the loop.
-///
 /// Similarly, TripMultiple divides the number of times that the LatchBlock may
 /// execute without exiting the loop.
 ///
@@ -207,10 +203,9 @@ static bool needToInsertPhisForLCSSA(Loop *L, std::vector<BasicBlock *> Blocks,
 /// DominatorTree if they are non-null.
 bool llvm::UnrollLoop(Loop *L, unsigned Count, unsigned TripCount, bool Force,
                       bool AllowRuntime, bool AllowExpensiveTripCount,
-                      bool PreserveCondBr, unsigned TripMultiple, LoopInfo *LI,
-                      ScalarEvolution *SE, DominatorTree *DT,
-                      AssumptionCache *AC, OptimizationRemarkEmitter *ORE,
-                      bool PreserveLCSSA) {
+                      unsigned TripMultiple, LoopInfo *LI, ScalarEvolution *SE,
+                      DominatorTree *DT, AssumptionCache *AC,
+                      OptimizationRemarkEmitter *ORE, bool PreserveLCSSA) {
   BasicBlock *Preheader = L->getLoopPreheader();
   if (!Preheader) {
     DEBUG(dbgs() << "  Can't unroll; loop preheader-insertion failed.\n");
@@ -544,16 +539,12 @@ bool llvm::UnrollLoop(Loop *L, unsigned Count, unsigned TripCount, bool Force,
     if (CompletelyUnroll) {
       if (j == 0)
         Dest = LoopExit;
-      // If using trip count upper bound to completely unroll, we need to keep
-      // the conditional branch except the last one because the loop may exit
-      // after any iteration.
-      assert(NeedConditional &&
-             "NeedCondition cannot be modified by both complete "
-             "unrolling and runtime unrolling");
-      NeedConditional = (PreserveCondBr && j);
-    } else if (j != BreakoutTrip && (TripMultiple == 0 || j % TripMultiple != 0)) {
-      // If we know the trip count or a multiple of it, we can safely use an
-      // unconditional branch for some iterations.
+      NeedConditional = false;
+    }
+
+    // If we know the trip count or a multiple of it, we can safely use an
+    // unconditional branch for some iterations.
+    if (j != BreakoutTrip && (TripMultiple == 0 || j % TripMultiple != 0)) {
       NeedConditional = false;
     }