1 files changed, 44 insertions, 0 deletions
diff --git a/include/llvm/Transforms/Utils/LCSSA.h b/include/llvm/Transforms/Utils/LCSSA.h
new file mode 100644
index 0000000000000..f0277d0215412
--- /dev/null
+++ b/include/llvm/Transforms/Utils/LCSSA.h
@@ -0,0 +1,44 @@
+//===- LCSSA.h - Loop-closed SSA transform Pass -----------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This pass transforms loops by placing phi nodes at the end of the loops for
+// all values that are live across the loop boundary.  For example, it turns
+// the left into the right code:
+//
+// for (...)                for (...)
+//   if (c)                   if (c)
+//     X1 = ...                 X1 = ...
+//   else                     else
+//     X2 = ...                 X2 = ...
+//   X3 = phi(X1, X2)         X3 = phi(X1, X2)
+// ... = X3 + 4             X4 = phi(X3)
+//                          ... = X4 + 4
+//
+// This is still valid LLVM; the extra phi nodes are purely redundant, and will
+// be trivially eliminated by InstCombine.  The major benefit of this
+// transformation is that it makes many other loop optimizations, such as
+// LoopUnswitching, simpler.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_TRANSFORMS_UTILS_LCSSA_H
+#define LLVM_TRANSFORMS_UTILS_LCSSA_H
+
+#include "llvm/IR/PassManager.h"
+
+namespace llvm {
+
+/// Converts loops into loop-closed SSA form.
+class LCSSAPass : public PassInfoMixin<LCSSAPass> {
+public:
+  PreservedAnalyses run(Function &F, AnalysisManager<Function> &AM);
+};
+} // end namespace llvm
+
+#endif // LLVM_TRANSFORMS_UTILS_LCSSA_H