LLVM  9.0.0svn
LCSSA.h
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1 //===- LCSSA.h - Loop-closed SSA transform Pass -----------------*- C++ -*-===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // This pass transforms loops by placing phi nodes at the end of the loops for
10 // all values that are live across the loop boundary. For example, it turns
11 // the left into the right code:
12 //
13 // for (...) for (...)
14 // if (c) if (c)
15 // X1 = ... X1 = ...
16 // else else
17 // X2 = ... X2 = ...
18 // X3 = phi(X1, X2) X3 = phi(X1, X2)
19 // ... = X3 + 4 X4 = phi(X3)
20 // ... = X4 + 4
21 //
22 // This is still valid LLVM; the extra phi nodes are purely redundant, and will
23 // be trivially eliminated by InstCombine. The major benefit of this
24 // transformation is that it makes many other loop optimizations, such as
25 // LoopUnswitching, simpler.
26 //
27 //===----------------------------------------------------------------------===//
28 
29 #ifndef LLVM_TRANSFORMS_UTILS_LCSSA_H
30 #define LLVM_TRANSFORMS_UTILS_LCSSA_H
31 
32 #include "llvm/IR/PassManager.h"
33 
34 namespace llvm {
35 
36 /// Converts loops into loop-closed SSA form.
37 class LCSSAPass : public PassInfoMixin<LCSSAPass> {
38 public:
40 };
41 } // end namespace llvm
42 
43 #endif // LLVM_TRANSFORMS_UTILS_LCSSA_H
Converts loops into loop-closed SSA form.
Definition: LCSSA.h:37
This class represents lattice values for constants.
Definition: AllocatorList.h:23
F(f)
A CRTP mix-in to automatically provide informational APIs needed for passes.
Definition: PassManager.h:372
A set of analyses that are preserved following a run of a transformation pass.
Definition: PassManager.h:153
PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM)
Definition: LCSSA.cpp:479
A container for analyses that lazily runs them and caches their results.
This header defines various interfaces for pass management in LLVM.