[LICM][NFC] Don't preserve DT and loop analyzes separately

[mkazantsev]

Summary

This is already implied by getLoopPassPreservedAnalyses.

[nikic]

These area already part of getLoopPassPreservedAnalyses().

[mkazantsev]

Is it? I was reading LICM code and it's like

PreservedAnalyses LICMPass::run(Loop &L, LoopAnalysisManager &AM,
                                LoopStandardAnalysisResults &AR, LPMUpdater &) {
  if (!AR.MSSA)
    report_fatal_error("LICM requires MemorySSA (loop-mssa)",
                       /*GenCrashDiag*/false);

  // For the new PM, we also can't use OptimizationRemarkEmitter as an analysis
  // pass.  Function analyses need to be preserved across loop transformations
  // but ORE cannot be preserved (see comment before the pass definition).
  OptimizationRemarkEmitter ORE(L.getHeader()->getParent());

  LoopInvariantCodeMotion LICM(Opts.MssaOptCap, Opts.MssaNoAccForPromotionCap,
                               Opts.AllowSpeculation);
  if (!LICM.runOnLoop(&L, &AR.AA, &AR.LI, &AR.DT, &AR.AC, &AR.TLI, &AR.TTI,
                      &AR.SE, AR.MSSA, &ORE))
    return PreservedAnalyses::all();

  auto PA = getLoopPassPreservedAnalyses();

  PA.preserve<DominatorTreeAnalysis>();
  PA.preserve<LoopAnalysis>();
  PA.preserve<MemorySSAAnalysis>();

  return PA;
}

Should we then remove it from there?

[skatkov]

In D144860#4157411, @mkazantsev wrote:

Is it? I was reading LICM code and it's like

PreservedAnalyses LICMPass::run(Loop &L, LoopAnalysisManager &AM,
                                LoopStandardAnalysisResults &AR, LPMUpdater &) {
  if (!AR.MSSA)
    report_fatal_error("LICM requires MemorySSA (loop-mssa)",
                       /*GenCrashDiag*/false);

  // For the new PM, we also can't use OptimizationRemarkEmitter as an analysis
  // pass.  Function analyses need to be preserved across loop transformations
  // but ORE cannot be preserved (see comment before the pass definition).
  OptimizationRemarkEmitter ORE(L.getHeader()->getParent());

  LoopInvariantCodeMotion LICM(Opts.MssaOptCap, Opts.MssaNoAccForPromotionCap,
                               Opts.AllowSpeculation);
  if (!LICM.runOnLoop(&L, &AR.AA, &AR.LI, &AR.DT, &AR.AC, &AR.TLI, &AR.TTI,
                      &AR.SE, AR.MSSA, &ORE))
    return PreservedAnalyses::all();

  auto PA = getLoopPassPreservedAnalyses();

  PA.preserve<DominatorTreeAnalysis>();
  PA.preserve<LoopAnalysis>();
  PA.preserve<MemorySSAAnalysis>();

  return PA;
}

Should we then remove it from there?

I think yes.

PreservedAnalyses llvm::getLoopPassPreservedAnalyses() {
  PreservedAnalyses PA;
  PA.preserve<DominatorTreeAnalysis>();
  PA.preserve<LoopAnalysis>();
  PA.preserve<LoopAnalysisManagerFunctionProxy>();
  PA.preserve<ScalarEvolutionAnalysis>();
  return PA;
}

[mkazantsev]

Okay :)

[nikic]

LGTM

llvm/lib/Transforms/Scalar/LICM.cpp

PreservedAnalyses LICMPass::run(Loop &L, LoopAnalysisManager &AM,
 
   LoopInvariantCodeMotion LICM(Opts.MssaOptCap, Opts.MssaNoAccForPromotionCap,
                                Opts.AllowSpeculation);
   if (!LICM.runOnLoop(&L, &AR.AA, &AR.LI, &AR.DT, &AR.AC, &AR.TLI, &AR.TTI,
                       &AR.SE, AR.MSSA, &ORE))
     return PreservedAnalyses::all();
 
   auto PA = getLoopPassPreservedAnalyses();
-
-  PA.preserve<DominatorTreeAnalysis>();
-  PA.preserve<LoopAnalysis>();
   PA.preserve<MemorySSAAnalysis>();
 
   return PA;
 }
 
 void LICMPass::printPipeline(
     raw_ostream &OS, function_ref<StringRef(StringRef)> MapClassName2PassName) {
   static_cast<PassInfoMixin<LICMPass> *>(this)->printPipeline(