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File indexing completed on 2026-05-10 08:44:43
0001 //===- LCSSA.h - Loop-closed SSA transform Pass -----------------*- C++ -*-===// 0002 // 0003 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 0004 // See https://llvm.org/LICENSE.txt for license information. 0005 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 0006 // 0007 //===----------------------------------------------------------------------===// 0008 // 0009 // This pass transforms loops by placing phi nodes at the end of the loops for 0010 // all values that are live across the loop boundary. For example, it turns 0011 // the left into the right code: 0012 // 0013 // for (...) for (...) 0014 // if (c) if (c) 0015 // X1 = ... X1 = ... 0016 // else else 0017 // X2 = ... X2 = ... 0018 // X3 = phi(X1, X2) X3 = phi(X1, X2) 0019 // ... = X3 + 4 X4 = phi(X3) 0020 // ... = X4 + 4 0021 // 0022 // This is still valid LLVM; the extra phi nodes are purely redundant, and will 0023 // be trivially eliminated by InstCombine. The major benefit of this 0024 // transformation is that it makes many other loop optimizations, such as 0025 // LoopUnswitching, simpler. 0026 // 0027 //===----------------------------------------------------------------------===// 0028 0029 #ifndef LLVM_TRANSFORMS_UTILS_LCSSA_H 0030 #define LLVM_TRANSFORMS_UTILS_LCSSA_H 0031 0032 #include "llvm/IR/PassManager.h" 0033 0034 namespace llvm { 0035 0036 /// Converts loops into loop-closed SSA form. 0037 class LCSSAPass : public PassInfoMixin<LCSSAPass> { 0038 public: 0039 PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM); 0040 }; 0041 } // end namespace llvm 0042 0043 #endif // LLVM_TRANSFORMS_UTILS_LCSSA_H
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