//===- LCSSA.h - Loop-closed SSA transform Pass -----------------*- C++ -*-===// // // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. // See https://llvm.org/LICENSE.txt for license information. // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception // //===----------------------------------------------------------------------===// // // 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, FunctionAnalysisManager &AM); }; } // end namespace llvm #endif // LLVM_TRANSFORMS_UTILS_LCSSA_H

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