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/Support/TimeProfiler.h"
10#include "llvm/Transforms/Scalar/LoopPassManager.h"
11#include "llvm/Analysis/LoopInfo.h"
12
13using namespace llvm;
14
15// Explicit template instantiations and specialization defininitions for core
16// template typedefs.
17namespace llvm {
18template class PassManager<Loop, LoopAnalysisManager,
19                           LoopStandardAnalysisResults &, LPMUpdater &>;
20
21/// Explicitly specialize the pass manager's run method to handle loop nest
22/// structure updates.
23template <>
24PreservedAnalyses
25PassManager<Loop, LoopAnalysisManager, LoopStandardAnalysisResults &,
26            LPMUpdater &>::run(Loop &L, LoopAnalysisManager &AM,
27                               LoopStandardAnalysisResults &AR, LPMUpdater &U) {
28  PreservedAnalyses PA = PreservedAnalyses::all();
29
30  if (DebugLogging)
31    dbgs() << "Starting Loop pass manager run.\n";
32
33  // Request PassInstrumentation from analysis manager, will use it to run
34  // instrumenting callbacks for the passes later.
35  PassInstrumentation PI = AM.getResult<PassInstrumentationAnalysis>(L, AR);
36  for (auto &Pass : Passes) {
37    // Check the PassInstrumentation's BeforePass callbacks before running the
38    // pass, skip its execution completely if asked to (callback returns false).
39    if (!PI.runBeforePass<Loop>(*Pass, L))
40      continue;
41
42    if (DebugLogging)
43      dbgs() << "Running pass: " << Pass->name() << " on " << L;
44
45    PreservedAnalyses PassPA;
46    {
47      TimeTraceScope TimeScope(Pass->name(), L.getName());
48      PassPA = Pass->run(L, AM, AR, U);
49    }
50
51    // do not pass deleted Loop into the instrumentation
52    if (U.skipCurrentLoop())
53      PI.runAfterPassInvalidated<Loop>(*Pass);
54    else
55      PI.runAfterPass<Loop>(*Pass, L);
56
57    // If the loop was deleted, abort the run and return to the outer walk.
58    if (U.skipCurrentLoop()) {
59      PA.intersect(std::move(PassPA));
60      break;
61    }
62
63#ifndef NDEBUG
64    // Verify the loop structure and LCSSA form before visiting the loop.
65    L.verifyLoop();
66    assert(L.isRecursivelyLCSSAForm(AR.DT, AR.LI) &&
67           "Loops must remain in LCSSA form!");
68#endif
69
70    // Update the analysis manager as each pass runs and potentially
71    // invalidates analyses.
72    AM.invalidate(L, PassPA);
73
74    // Finally, we intersect the final preserved analyses to compute the
75    // aggregate preserved set for this pass manager.
76    PA.intersect(std::move(PassPA));
77
78    // FIXME: Historically, the pass managers all called the LLVM context's
79    // yield function here. We don't have a generic way to acquire the
80    // context and it isn't yet clear what the right pattern is for yielding
81    // in the new pass manager so it is currently omitted.
82    // ...getContext().yield();
83  }
84
85  // Invalidation for the current loop should be handled above, and other loop
86  // analysis results shouldn't be impacted by runs over this loop. Therefore,
87  // the remaining analysis results in the AnalysisManager are preserved. We
88  // mark this with a set so that we don't need to inspect each one
89  // individually.
90  // FIXME: This isn't correct! This loop and all nested loops' analyses should
91  // be preserved, but unrolling should invalidate the parent loop's analyses.
92  PA.preserveSet<AllAnalysesOn<Loop>>();
93
94  if (DebugLogging)
95    dbgs() << "Finished Loop pass manager run.\n";
96
97  return PA;
98}
99}
100
101PrintLoopPass::PrintLoopPass() : OS(dbgs()) {}
102PrintLoopPass::PrintLoopPass(raw_ostream &OS, const std::string &Banner)
103    : OS(OS), Banner(Banner) {}
104
105PreservedAnalyses PrintLoopPass::run(Loop &L, LoopAnalysisManager &,
106                                     LoopStandardAnalysisResults &,
107                                     LPMUpdater &) {
108  printLoop(L, OS, Banner);
109  return PreservedAnalyses::all();
110}
111