[LoopUnrollRuntime] Bailout when multiple exiting blocks to the unique latch exit...

Currently, we do not support multiple exiting blocks to the
latch exit block. However, this bailout wasn't triggered when we had a
unique exit block (which is the latch exit), with multiple exiting
blocks to that unique exit.

Moved the bailout so that it's triggered in both cases and added
testcase.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@307291 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Transforms/Utils/LoopUnrollRuntime.cpp b/lib/Transforms/Utils/LoopUnrollRuntime.cpp
index 9ad2b707e6b236743c15dc4a04683d8b70f6fe0e..f96c0bd149a0e9f99d502c08d6fada37ec7b5fc6 100644 (file)
--- a/lib/Transforms/Utils/LoopUnrollRuntime.cpp
+++ b/lib/Transforms/Utils/LoopUnrollRuntime.cpp
@@ -504,10 +504,6 @@ bool llvm::UnrollRuntimeLoopRemainder(Loop *L, unsigned Count,
     // transformed.
     if (!PreserveLCSSA)
       return false;
-    // TODO: Support multiple exiting blocks jumping to the `LatchExit`. This
-    // will need updating the logic in connectEpilog.
-    if (!LatchExit->getSinglePredecessor())
-        return false;
     SmallVector<BasicBlock *, 4> Exits;
     L->getUniqueExitBlocks(Exits);
     for (auto *BB : Exits)
@@ -517,6 +513,11 @@ bool llvm::UnrollRuntimeLoopRemainder(Loop *L, unsigned Count,
 
   assert(LatchExit && "Latch Exit should exist!");
 
+  // TODO: Support multiple exiting blocks jumping to the `LatchExit` when
+  // UnrollRuntimeMultiExit is true. This will need updating the logic in
+  // connectEpilog.
+  if (!LatchExit->getSinglePredecessor())
+    return false;
   // Use Scalar Evolution to compute the trip count. This allows more loops to
   // be unrolled than relying on induction var simplification.
   if (!SE)

diff --git a/test/Transforms/LoopUnroll/runtime-loop-multiple-exits.ll b/test/Transforms/LoopUnroll/runtime-loop-multiple-exits.ll
index 1f31a133e34d9a583c0af4fa792198e251d5be77..5cff94906d8ec939d8d336677fd82b32d2b1a8b4 100644 (file)
--- a/test/Transforms/LoopUnroll/runtime-loop-multiple-exits.ll
+++ b/test/Transforms/LoopUnroll/runtime-loop-multiple-exits.ll
@@ -184,6 +184,36 @@ for.exit2:
   ret i32 42
 }
 
+; FIXME: Support multiple exiting blocks to the unique exit block.
+define void @unique_exit(i32 %arg) {
+; CHECK-LABEL: unique_exit
+; CHECK-NOT: .unr
+; CHECK-NOT: .epil
+entry:
+  %tmp = icmp sgt i32 undef, %arg
+  br i1 %tmp, label %preheader, label %returnblock
+
+preheader:                                 ; preds = %entry
+  br label %header
+
+LoopExit:                                ; preds = %header, %latch
+  %tmp2.ph = phi i32 [ %tmp4, %header ], [ -1, %latch ]
+  br label %returnblock
+
+returnblock:                                         ; preds = %LoopExit, %entry
+  %tmp2 = phi i32 [ -1, %entry ], [ %tmp2.ph, %LoopExit ]
+  ret void
+
+header:                                           ; preds = %preheader, %latch
+  %tmp4 = phi i32 [ %inc, %latch ], [ %arg, %preheader ]
+  %inc = add nsw i32 %tmp4, 1
+  br i1 true, label %LoopExit, label %latch
+
+latch:                                            ; preds = %header
+  %cmp = icmp slt i32 %inc, undef
+  br i1 %cmp, label %header, label %LoopExit
+}
+
 ; two exiting and two exit blocks.
 ; the non-latch exiting block has duplicate edges to the non-latch exit block.
 define i64 @test5(i64 %trip, i64 %add, i1 %cond) {