LLVM 17.0.0git
LoopSimplify.h
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1//===- LoopSimplify.h - Loop Canonicalization 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 performs several transformations to transform natural loops into a
10// simpler form, which makes subsequent analyses and transformations simpler and
11// more effective.
12//
13// Loop pre-header insertion guarantees that there is a single, non-critical
14// entry edge from outside of the loop to the loop header. This simplifies a
15// number of analyses and transformations, such as LICM.
16//
17// Loop exit-block insertion guarantees that all exit blocks from the loop
18// (blocks which are outside of the loop that have predecessors inside of the
19// loop) only have predecessors from inside of the loop (and are thus dominated
20// by the loop header). This simplifies transformations such as store-sinking
21// that are built into LICM.
22//
23// This pass also guarantees that loops will have exactly one backedge.
24//
25// Indirectbr instructions introduce several complications. If the loop
26// contains or is entered by an indirectbr instruction, it may not be possible
27// to transform the loop and make these guarantees. Client code should check
28// that these conditions are true before relying on them.
29//
30// Note that the simplifycfg pass will clean up blocks which are split out but
31// end up being unnecessary, so usage of this pass should not pessimize
32// generated code.
33//
34// This pass obviously modifies the CFG, but updates loop information and
35// dominator information.
36//
37//===----------------------------------------------------------------------===//
38#ifndef LLVM_TRANSFORMS_UTILS_LOOPSIMPLIFY_H
39#define LLVM_TRANSFORMS_UTILS_LOOPSIMPLIFY_H
40
41#include "llvm/IR/PassManager.h"
42
43namespace llvm {
44
45class AssumptionCache;
46class DominatorTree;
47class Loop;
48class LoopInfo;
49class MemorySSAUpdater;
50class ScalarEvolution;
51
52/// This pass is responsible for loop canonicalization.
53class LoopSimplifyPass : public PassInfoMixin<LoopSimplifyPass> {
54public:
56};
57
58/// Simplify each loop in a loop nest recursively.
59///
60/// This takes a potentially un-simplified loop L (and its children) and turns
61/// it into a simplified loop nest with preheaders and single backedges. It will
62/// update \c DominatorTree, \c LoopInfo, \c ScalarEvolution and \c MemorySSA
63/// analyses if they're non-null, and LCSSA if \c PreserveLCSSA is true.
66 bool PreserveLCSSA);
67
68} // end namespace llvm
69
70#endif // LLVM_TRANSFORMS_UTILS_LOOPSIMPLIFY_H
#define F(x, y, z)
Definition: MD5.cpp:55
This header defines various interfaces for pass management in LLVM.
A container for analyses that lazily runs them and caches their results.
Definition: PassManager.h:620
A cache of @llvm.assume calls within a function.
Concrete subclass of DominatorTreeBase that is used to compute a normal dominator tree.
Definition: Dominators.h:166
This pass is responsible for loop canonicalization.
Definition: LoopSimplify.h:53
PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM)
Represents a single loop in the control flow graph.
Definition: LoopInfo.h:547
A set of analyses that are preserved following a run of a transformation pass.
Definition: PassManager.h:152
The main scalar evolution driver.
This is an optimization pass for GlobalISel generic memory operations.
Definition: AddressRanges.h:18
bool simplifyLoop(Loop *L, DominatorTree *DT, LoopInfo *LI, ScalarEvolution *SE, AssumptionCache *AC, MemorySSAUpdater *MSSAU, bool PreserveLCSSA)
Simplify each loop in a loop nest recursively.
A CRTP mix-in to automatically provide informational APIs needed for passes.
Definition: PassManager.h:371