[llvm] r307417 - [LoopUnrollRuntime] NFC: use the precomputed loop exit in ConnectProlog

[Anna Thomas via llvm-commits]

Author: annat
Date: Fri Jul  7 11:05:28 2017
New Revision: 307417

URL: http://llvm.org/viewvc/llvm-project?rev=307417&view=rev
Log:
[LoopUnrollRuntime] NFC: use the precomputed loop exit in ConnectProlog

Minor refactoring to use the preexisting loop exit that's already
calculated. We do not need to recompute the loop exit in ConnectProlog.
Apart from avoiding redundant computation, this is required for
supporting multiple loop exits when Prolog remainder loops are generated.

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

Modified: llvm/trunk/lib/Transforms/Utils/LoopUnrollRuntime.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/LoopUnrollRuntime.cpp?rev=307417&r1=307416&r2=307417&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Utils/LoopUnrollRuntime.cpp (original)
+++ llvm/trunk/lib/Transforms/Utils/LoopUnrollRuntime.cpp Fri Jul  7 11:05:28 2017
@@ -65,9 +65,11 @@ static cl::opt<bool> UnrollRuntimeMultiE
 ///   than the unroll factor.
 ///
 static void ConnectProlog(Loop *L, Value *BECount, unsigned Count,
-                          BasicBlock *PrologExit, BasicBlock *PreHeader,
-                          BasicBlock *NewPreHeader, ValueToValueMapTy &VMap,
-                          DominatorTree *DT, LoopInfo *LI, bool PreserveLCSSA) {
+                          BasicBlock *PrologExit,
+                          BasicBlock *OriginalLoopLatchExit,
+                          BasicBlock *PreHeader, BasicBlock *NewPreHeader,
+                          ValueToValueMapTy &VMap, DominatorTree *DT,
+                          LoopInfo *LI, bool PreserveLCSSA) {
   BasicBlock *Latch = L->getLoopLatch();
   assert(Latch && "Loop must have a latch");
   BasicBlock *PrologLatch = cast<BasicBlock>(VMap[Latch]);
@@ -142,17 +144,15 @@ static void ConnectProlog(Loop *L, Value
   // then (BECount + 1) cannot unsigned-overflow.
   Value *BrLoopExit =
       B.CreateICmpULT(BECount, ConstantInt::get(BECount->getType(), Count - 1));
-  BasicBlock *Exit = L->getUniqueExitBlock();
-  assert(Exit && "Loop must have a single exit block only");
   // Split the exit to maintain loop canonicalization guarantees
-  SmallVector<BasicBlock*, 4> Preds(predecessors(Exit));
-  SplitBlockPredecessors(Exit, Preds, ".unr-lcssa", DT, LI,
+  SmallVector<BasicBlock *, 4> Preds(predecessors(OriginalLoopLatchExit));
+  SplitBlockPredecessors(OriginalLoopLatchExit, Preds, ".unr-lcssa", DT, LI,
                          PreserveLCSSA);
   // Add the branch to the exit block (around the unrolled loop)
-  B.CreateCondBr(BrLoopExit, Exit, NewPreHeader);
+  B.CreateCondBr(BrLoopExit, OriginalLoopLatchExit, NewPreHeader);
   InsertPt->eraseFromParent();
   if (DT)
-    DT->changeImmediateDominator(Exit, PrologExit);
+    DT->changeImmediateDominator(OriginalLoopLatchExit, PrologExit);
 }
 
 /// Connect the unrolling epilog code to the original loop.
@@ -782,8 +782,8 @@ bool llvm::UnrollRuntimeLoopRemainder(Lo
   } else {
     // Connect the prolog code to the original loop and update the
     // PHI functions.
-    ConnectProlog(L, BECount, Count, PrologExit, PreHeader, NewPreHeader,
-                  VMap, DT, LI, PreserveLCSSA);
+    ConnectProlog(L, BECount, Count, PrologExit, LatchExit, PreHeader,
+                  NewPreHeader, VMap, DT, LI, PreserveLCSSA);
   }
 
   // If this loop is nested, then the loop unroller changes the code in the