[LoopUnroll] Ensure we create prolog loops in simplified form.

llvm-svn: 277502

2 files changed, 13 insertions, 1 deletions

diff --git a/llvm/lib/Transforms/Utils/LoopUnrollRuntime.cpp b/llvm/lib/Transforms/Utils/LoopUnrollRuntime.cpp
index 861a50cf354..16197a9206e 100644
--- a/llvm/lib/Transforms/Utils/LoopUnrollRuntime.cpp
+++ b/llvm/lib/Transforms/Utils/LoopUnrollRuntime.cpp
@@ -112,6 +112,18 @@ static void ConnectProlog(Loop *L, Value *BECount, unsigned Count,
     }
   }
 
+  // Make sure that created prolog loop is in simplified form
+  SmallVector<BasicBlock *, 4> PrologExitPreds;
+  Loop *PrologLoop = LI->getLoopFor(PrologLatch);
+  if (PrologLoop) {
+    for (BasicBlock *PredBB : predecessors(PrologExit))
+      if (PrologLoop->contains(PredBB))
+        PrologExitPreds.push_back(PredBB);
+
+    SplitBlockPredecessors(PrologExit, PrologExitPreds, ".unr-lcssa", DT, LI,
+                           PreserveLCSSA);
+  }
+
   // Create a branch around the original loop, which is taken if there are no
   // iterations remaining to be executed after running the prologue.
   Instruction *InsertPt = PrologExit->getTerminator();
diff --git a/llvm/test/Transforms/LoopUnroll/runtime-loop.ll b/llvm/test/Transforms/LoopUnroll/runtime-loop.ll
index 2fc4dbd26c7..d1b5f84661b 100644
--- a/llvm/test/Transforms/LoopUnroll/runtime-loop.ll
+++ b/llvm/test/Transforms/LoopUnroll/runtime-loop.ll
@@ -23,7 +23,7 @@ target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f3
 ; PROLOG: %indvars.iv.prol = phi i64 [ %indvars.iv.next.prol, %for.body.prol ], [ 0, %for.body.prol.preheader ]
 ; PROLOG:  %prol.iter.sub = sub i32 %prol.iter, 1
 ; PROLOG:  %prol.iter.cmp = icmp ne i32 %prol.iter.sub, 0
-; PROLOG:  br i1 %prol.iter.cmp, label %for.body.prol, label %for.body.prol.loopexit, !llvm.loop !0
+; PROLOG:  br i1 %prol.iter.cmp, label %for.body.prol, label %for.body.prol.loopexit.unr-lcssa, !llvm.loop !0
 
 
 define i32 @test(i32* nocapture %a, i32 %n) nounwind uwtable readonly {