Fix PR3408 by making a non-obvious assumption very obvious, and
handling the flaw inherent in that assumption. :)
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@62984 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Scalar/LoopRotation.cpp b/lib/Transforms/Scalar/LoopRotation.cpp
index 1118ed5..aed84e2 100644
--- a/lib/Transforms/Scalar/LoopRotation.cpp
+++ b/lib/Transforms/Scalar/LoopRotation.cpp
@@ -12,7 +12,6 @@
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "loop-rotate"
-
#include "llvm/Transforms/Scalar.h"
#include "llvm/Function.h"
#include "llvm/Instructions.h"
@@ -26,7 +25,6 @@
#include "llvm/Support/Debug.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/SmallVector.h"
-
using namespace llvm;
#define MAX_HEADER_SIZE 16
@@ -178,6 +176,12 @@
assert(NewHeader && "Unable to determine new loop header");
assert(L->contains(NewHeader) && !L->contains(Exit) &&
"Unable to determine loop header and exit blocks");
+
+ // This code assumes that new header has exactly one predecessor. Remove any
+ // single entry PHI nodes in it.
+ assert(NewHeader->getSinglePredecessor() &&
+ "New header doesn't have one pred!");
+ FoldSingleEntryPHINodes(NewHeader);
// Copy PHI nodes and other instructions from original header
// into original pre-header. Unlike original header, original pre-header is