1//===- LoopPassManager.cpp - Loop pass management -------------------------===//
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#include "llvm/Transforms/Scalar/LoopPassManager.h"
10#include "llvm/Analysis/LoopInfo.h"
11
12using namespace llvm;
13
14// Explicit template instantiations and specialization defininitions for core
15// template typedefs.
16namespace llvm {
17template class PassManager<Loop, LoopAnalysisManager,
18                           LoopStandardAnalysisResults &, LPMUpdater &>;
19
20/// Explicitly specialize the pass manager's run method to handle loop nest
21/// structure updates.
22template <>
23PreservedAnalyses
24PassManager<Loop, LoopAnalysisManager, LoopStandardAnalysisResults &,
25            LPMUpdater &>::run(Loop &L, LoopAnalysisManager &AM,
26                               LoopStandardAnalysisResults &AR, LPMUpdater &U) {
27  PreservedAnalyses PA = PreservedAnalyses::all();
28
29  if (DebugLogging)
30    dbgs() << "Starting Loop pass manager run.\n";
31
32  // Request PassInstrumentation from analysis manager, will use it to run
33  // instrumenting callbacks for the passes later.
34  PassInstrumentation PI = AM.getResult<PassInstrumentationAnalysis>(L, AR);
35  for (auto &Pass : Passes) {
36    if (DebugLogging)
37      dbgs() << "Running pass: " << Pass->name() << " on " << L;
38
39    // Check the PassInstrumentation's BeforePass callbacks before running the
40    // pass, skip its execution completely if asked to (callback returns false).
41    if (!PI.runBeforePass<Loop>(*Pass, L))
42      continue;
43
44    PreservedAnalyses PassPA = Pass->run(L, AM, AR, U);
45
46    // do not pass deleted Loop into the instrumentation
47    if (U.skipCurrentLoop())
48      PI.runAfterPassInvalidated<Loop>(*Pass);
49    else
50      PI.runAfterPass<Loop>(*Pass, L);
51
52    // If the loop was deleted, abort the run and return to the outer walk.
53    if (U.skipCurrentLoop()) {
54      PA.intersect(std::move(PassPA));
55      break;
56    }
57
58#ifndef NDEBUG
59    // Verify the loop structure and LCSSA form before visiting the loop.
60    L.verifyLoop();
61    assert(L.isRecursivelyLCSSAForm(AR.DT, AR.LI) &&
62           "Loops must remain in LCSSA form!");
63#endif
64
65    // Update the analysis manager as each pass runs and potentially
66    // invalidates analyses.
67    AM.invalidate(L, PassPA);
68
69    // Finally, we intersect the final preserved analyses to compute the
70    // aggregate preserved set for this pass manager.
71    PA.intersect(std::move(PassPA));
72
73    // FIXME: Historically, the pass managers all called the LLVM context's
74    // yield function here. We don't have a generic way to acquire the
75    // context and it isn't yet clear what the right pattern is for yielding
76    // in the new pass manager so it is currently omitted.
77    // ...getContext().yield();
78  }
79
80  // Invalidation for the current loop should be handled above, and other loop
81  // analysis results shouldn't be impacted by runs over this loop. Therefore,
82  // the remaining analysis results in the AnalysisManager are preserved. We
83  // mark this with a set so that we don't need to inspect each one
84  // individually.
85  // FIXME: This isn't correct! This loop and all nested loops' analyses should
86  // be preserved, but unrolling should invalidate the parent loop's analyses.
87  PA.preserveSet<AllAnalysesOn<Loop>>();
88
89  if (DebugLogging)
90    dbgs() << "Finished Loop pass manager run.\n";
91
92  return PA;
93}
94}
95
96PrintLoopPass::PrintLoopPass() : OS(dbgs()) {}
97PrintLoopPass::PrintLoopPass(raw_ostream &OS, const std::string &Banner)
98    : OS(OS), Banner(Banner) {}
99
100PreservedAnalyses PrintLoopPass::run(Loop &L, LoopAnalysisManager &,
101                                     LoopStandardAnalysisResults &,
102                                     LPMUpdater &) {
103  printLoop(L, OS, Banner);
104  return PreservedAnalyses::all();
105}
106