44 lines
1.6 KiB
C++
44 lines
1.6 KiB
C++
//===- 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
|