Revert "[LoopNest][LoopFlatten] Change LoopFlattenPass to LoopNest pass"

[eopXD]

Summary

This reverts commit 7952ddb21fb7e086d5a6f97767f235d2f6ae2176.

Originally opened this division upon receiving remote build failure notifications.
I was trying to revert my build failure with this patch , but I have just reverted my patch with git.
This diff is closed and not needed.

[eopXD]

Reverted the change in the origin diff: https://reviews.llvm.org/D102904

[lebedev.ri]

Please remember to actually mention *why* the change happens, not just what happens.

[eopXD]

@lebedev.ri I apologize for the unclear descriptions.

I am reverting my commit upon receiving multiple remote build failure notification emails.
I had reopened my original patch (mentioned above) and will investigate on the failure.

Thank you for leaving a comment.

llvm/include/llvm/Transforms/Scalar/LoopFlatten.h

 #include "llvm/Transforms/Scalar/LoopPassManager.h"
 
 namespace llvm {
 
 class LoopFlattenPass : public PassInfoMixin<LoopFlattenPass> {
 public:
   LoopFlattenPass() = default;
 
-  PreservedAnalyses run(LoopNest &LN, LoopAnalysisManager &LAM,
-                        LoopStandardAnalysisResults &AR, LPMUpdater &U);
+  PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM);
 };
 
 } // end namespace llvm
 
 #endif // LLVM_TRANSFORMS_SCALAR_LOOPFLATTEN_H

llvm/lib/Passes/PassBuilder.cpp

PassBuilder::buildO1FunctionSimplificationPipeline(OptimizationLevel Level,
   FPM.addPass(
       RequireAnalysisPass<OptimizationRemarkEmitterAnalysis, Function>());
   FPM.addPass(createFunctionToLoopPassAdaptor(std::move(LPM1),
                                               EnableMSSALoopDependency,
                                               /*UseBlockFrequencyInfo=*/true));
   FPM.addPass(SimplifyCFGPass());
   FPM.addPass(InstCombinePass());
   if (EnableLoopFlatten)
-    FPM.addPass(createFunctionToLoopPassAdaptor(LoopFlattenPass()));
+    FPM.addPass(LoopFlattenPass());
   // The loop passes in LPM2 (LoopFullUnrollPass) do not preserve MemorySSA.
   // *All* loop passes must preserve it, in order to be able to use it.
   FPM.addPass(createFunctionToLoopPassAdaptor(std::move(LPM2),
                                               /*UseMemorySSA=*/false,
                                               /*UseBlockFrequencyInfo=*/false));
 
   // Delete small array after loop unroll.
   FPM.addPass(SROA());
PassBuilder::buildFunctionSimplificationPipeline(OptimizationLevel Level,
   FPM.addPass(
       RequireAnalysisPass<OptimizationRemarkEmitterAnalysis, Function>());
   FPM.addPass(createFunctionToLoopPassAdaptor(std::move(LPM1),
                                               EnableMSSALoopDependency,
                                               /*UseBlockFrequencyInfo=*/true));
   FPM.addPass(SimplifyCFGPass());
   FPM.addPass(InstCombinePass());
   if (EnableLoopFlatten)
-    FPM.addPass(createFunctionToLoopPassAdaptor(LoopFlattenPass()));
+    FPM.addPass(LoopFlattenPass());
   // The loop passes in LPM2 (LoopIdiomRecognizePass, IndVarSimplifyPass,
   // LoopDeletionPass and LoopFullUnrollPass) do not preserve MemorySSA.
   // *All* loop passes must preserve it, in order to be able to use it.
   FPM.addPass(createFunctionToLoopPassAdaptor(std::move(LPM2),
                                               /*UseMemorySSA=*/false,
                                               /*UseBlockFrequencyInfo=*/false));
 
   // Delete small array after loop unroll.
PassBuilder::buildLTODefaultPipeline(OptimizationLevel Level,
   MainFPM.addPass(MemCpyOptPass());
 
   // Nuke dead stores.
   MainFPM.addPass(DSEPass());
   MainFPM.addPass(MergedLoadStoreMotionPass());
 
   // More loops are countable; try to optimize them.
   if (EnableLoopFlatten && Level.getSpeedupLevel() > 1)
-    MainFPM.addPass(createFunctionToLoopPassAdaptor(LoopFlattenPass()));
+    MainFPM.addPass(LoopFlattenPass());
 
   if (EnableConstraintElimination)
     MainFPM.addPass(ConstraintEliminationPass());
 
   LoopPassManager LPM;
   LPM.addPass(IndVarSimplifyPass());
   LPM.addPass(LoopDeletionPass());
   // FIXME: Add loop interchange.

llvm/lib/Passes/PassRegistry.def

 FUNCTION_PASS("lower-constant-intrinsics", LowerConstantIntrinsicsPass())
 FUNCTION_PASS("lower-matrix-intrinsics", LowerMatrixIntrinsicsPass())
 FUNCTION_PASS("lower-matrix-intrinsics-minimal", LowerMatrixIntrinsicsPass(true))
 FUNCTION_PASS("lower-widenable-condition", LowerWidenableConditionPass())
 FUNCTION_PASS("guard-widening", GuardWideningPass())
 FUNCTION_PASS("load-store-vectorizer", LoadStoreVectorizerPass())
 FUNCTION_PASS("loop-simplify", LoopSimplifyPass())
 FUNCTION_PASS("loop-sink", LoopSinkPass())
-FUNCTION_PASS("loop-unroll-and-jam", LoopUnrollAndJamPass())
+FUNCTION_PASS("loop-flatten", LoopFlattenPass())
 FUNCTION_PASS("lowerinvoke", LowerInvokePass())
 FUNCTION_PASS("lowerswitch", LowerSwitchPass())
 FUNCTION_PASS("mem2reg", PromotePass())
 FUNCTION_PASS("memcpyopt", MemCpyOptPass())
 FUNCTION_PASS("mergeicmps", MergeICmpsPass())
 FUNCTION_PASS("mergereturn", UnifyFunctionExitNodesPass())
 FUNCTION_PASS("nary-reassociate", NaryReassociatePass())
 FUNCTION_PASS("newgvn", NewGVNPass())

 
 #ifndef LOOP_PASS
 #define LOOP_PASS(NAME, CREATE_PASS)
 #endif
 LOOP_PASS("canon-freeze", CanonicalizeFreezeInLoopsPass())
 LOOP_PASS("dot-ddg", DDGDotPrinterPass())
 LOOP_PASS("invalidate<all>", InvalidateAllAnalysesPass())
 LOOP_PASS("licm", LICMPass())
-LOOP_PASS("loop-flatten", LoopFlattenPass())
 LOOP_PASS("loop-idiom", LoopIdiomRecognizePass())
 LOOP_PASS("loop-instsimplify", LoopInstSimplifyPass())
 LOOP_PASS("loop-interchange", LoopInterchangePass())
 LOOP_PASS("loop-rotate", LoopRotatePass())
 LOOP_PASS("no-op-loop", NoOpLoopPass())
 LOOP_PASS("print", PrintLoopPass(dbgs()))
 LOOP_PASS("loop-deletion", LoopDeletionPass())
 LOOP_PASS("loop-simplifycfg", LoopSimplifyCFGPass())

llvm/lib/Transforms/Scalar/LoopFlatten.cpp

if (OR == OverflowResult::AlwaysOverflowsHigh ||
     LLVM_DEBUG(dbgs() << "Multiply might overflow, not flattening\n");
     return false;
   }
 
   LLVM_DEBUG(dbgs() << "Multiply cannot overflow, modifying loop in-place\n");
   return DoFlattenLoopPair(FI, DT, LI, SE, AC, TTI);
 }
 
-bool Flatten(LoopNest &LN, DominatorTree *DT, LoopInfo *LI, ScalarEvolution *SE,
+bool Flatten(DominatorTree *DT, LoopInfo *LI, ScalarEvolution *SE,
              AssumptionCache *AC, TargetTransformInfo *TTI) {
   bool Changed = false;
-  for (Loop *InnerLoop : LN.getLoops()) {
+  for (auto *InnerLoop : LI->getLoopsInPreorder()) {
     auto *OuterLoop = InnerLoop->getParentLoop();
     if (!OuterLoop)
       continue;
     FlattenInfo FI(OuterLoop, InnerLoop);
     Changed |= FlattenLoopPair(FI, DT, LI, SE, AC, TTI);
   }
   return Changed;
 }
 
-PreservedAnalyses LoopFlattenPass::run(LoopNest &LN, LoopAnalysisManager &LAM,
-                                       LoopStandardAnalysisResults &AR,
-                                       LPMUpdater &U) {
+PreservedAnalyses LoopFlattenPass::run(Function &F,
+                                       FunctionAnalysisManager &AM) {
+  auto *DT = &AM.getResult<DominatorTreeAnalysis>(F);
+  auto *LI = &AM.getResult<LoopAnalysis>(F);
+  auto *SE = &AM.getResult<ScalarEvolutionAnalysis>(F);
+  auto *AC = &AM.getResult<AssumptionAnalysis>(F);
+  auto *TTI = &AM.getResult<TargetIRAnalysis>(F);
 
   bool Changed = false;
 
   // The loop flattening pass requires loops to be
   // in simplified form, and also needs LCSSA. Running
   // this pass will simplify all loops that contain inner loops,
   // regardless of whether anything ends up being flattened.
-  Changed |= Flatten(LN, &AR.DT, &AR.LI, &AR.SE, &AR.AC, &AR.TTI);
+  for (const auto &L : *LI) {
+    if (L->isInnermost())
+      continue;
+    Changed |=
+        simplifyLoop(L, DT, LI, SE, AC, nullptr, false /* PreserveLCSSA */);
+    Changed |= formLCSSARecursively(*L, *DT, LI, SE);
+  }
+
+  Changed |= Flatten(DT, LI, SE, AC, TTI);
 
   if (!Changed)
     return PreservedAnalyses::all();
 
   return PreservedAnalyses::none();
 }
 
 namespace {

 bool LoopFlattenLegacyPass::runOnFunction(Function &F) {
   ScalarEvolution *SE = &getAnalysis<ScalarEvolutionWrapperPass>().getSE();
   LoopInfo *LI = &getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
   auto *DTWP = getAnalysisIfAvailable<DominatorTreeWrapperPass>();
   DominatorTree *DT = DTWP ? &DTWP->getDomTree() : nullptr;
   auto &TTIP = getAnalysis<TargetTransformInfoWrapperPass>();
   auto *TTI = &TTIP.getTTI(F);
   auto *AC = &getAnalysis<AssumptionCacheTracker>().getAssumptionCache(F);
-  bool Changed = false;
-  for (Loop *L : *LI) {
-    auto LN = LoopNest::getLoopNest(*L, *SE);
-    Changed |= Flatten(*LN, DT, LI, SE, AC, TTI);
-  }
-  return Changed;
+  return Flatten(DT, LI, SE, AC, TTI);
 }