[PM] Enable the main loop pass pipelines with everything but loop-unswitch in the main pipelines for the new PM.

[chandlerc]

Summary

All of these now work, and Clang built using this builds and passes the
LLVM test suite.

Depends on D28897.

[davide]

LGTM

lib/Passes/PassBuilder.cpp

PassBuilder::buildFunctionSimplificationPipeline(OptimizationLevel Level,
   // FIXME: Currently this is split into two loop pass pipelines because we run
   // some function passes in between them. These can and should be replaced by
   // loop pass equivalenst but those aren't ready yet. Specifically,
   // `SimplifyCFGPass` and `InstCombinePass` are used. We have
   // `LoopSimplifyCFGPass` which isn't yet powerful enough, and the closest to
   // the other we have is `LoopInstSimplify`.
   LoopPassManager LPM1(DebugLogging), LPM2(DebugLogging);
 
-  // FIXME: Enable these when the loop pass manager can support enforcing loop
-  // simplified and LCSSA form as well as updating the loop nest after
-  // transformations and we finsih porting the loop passes.
-#if 0
   // Rotate Loop - disable header duplication at -Oz
   LPM1.addPass(LoopRotatePass(Level != Oz));
   LPM1.addPass(LICMPass());
+#if 0
+  // The LoopUnswitch pass isn't yet ported to the new pass manager.
   LPM1.addPass(LoopUnswitchPass(/* OptimizeForSize */ Level != O3));
+#endif
   LPM2.addPass(IndVarSimplifyPass());
-  LPM2.addPass(LoopIdiomPass());
+  LPM2.addPass(LoopIdiomRecognizePass());
   LPM2.addPass(LoopDeletionPass());
-  LPM2.addPass(SimpleLoopUnrollPass());
-#endif
+  LPM2.addPass(LoopUnrollPass::createFull());
+
   FPM.addPass(createFunctionToLoopPassAdaptor(std::move(LPM1)));
   FPM.addPass(SimplifyCFGPass());
   FPM.addPass(InstCombinePass());
   FPM.addPass(createFunctionToLoopPassAdaptor(std::move(LPM2)));
 
   // Eliminate redundancies.
   if (Level != O1) {
     // These passes add substantial compile time so skip them at O1.
#endif
   // opportunities opened up by them.
   FPM.addPass(InstCombinePass());
 
   // Re-consider control flow based optimizations after redundancy elimination,
   // redo DCE, etc.
   FPM.addPass(JumpThreadingPass());
   FPM.addPass(CorrelatedValuePropagationPass());
   FPM.addPass(DSEPass());
-  // FIXME: Enable this when the loop pass manager can support enforcing loop
-  // simplified and LCSSA form as well as updating the loop nest after
-  // transformations and we finsih porting the loop passes.
-#if 0
   FPM.addPass(createFunctionToLoopPassAdaptor(LICMPass()));
-#endif
 
   // Finally, do an expensive DCE pass to catch all the dead code exposed by
   // the simplifications and basic cleanup after all the simplifications.
   FPM.addPass(ADCEPass());
   FPM.addPass(SimplifyCFGPass());
   FPM.addPass(InstCombinePass());
 
   return FPM;

test/Other/new-pm-defaults.ll

 ; CHECK-O-NEXT: Running pass: TailCallElimPass
 ; CHECK-O-NEXT: Running pass: SimplifyCFGPass
 ; CHECK-O-NEXT: Running pass: ReassociatePass
 ; CHECK-O-NEXT: Running pass: FunctionToLoopPassAdaptor<{{.*}}LoopStandardAnalysisResults{{.*}}>
 ; CHECK-O-NEXT: Running analysis: LoopAnalysis
 ; CHECK-O-NEXT: Running analysis: InnerAnalysisManagerProxy
 ; CHECK-O-NEXT: Running analysis: ScalarEvolutionAnalysis
 ; CHECK-O-NEXT: Starting Loop pass manager run.
+; CHECK-O-NEXT: Running pass: LoopRotatePass
+; CHECK-O-NEXT: Running pass: LICM
+; CHECK-O-NEXT: Running analysis: OuterAnalysisManagerProxy
 ; CHECK-O-NEXT: Finished Loop pass manager run.
 ; CHECK-O-NEXT: Running pass: SimplifyCFGPass
 ; CHECK-O-NEXT: Running pass: InstCombinePass
 ; CHECK-O-NEXT: Running pass: FunctionToLoopPassAdaptor<{{.*}}LoopStandardAnalysisResults{{.*}}>
 ; CHECK-O-NEXT: Starting Loop pass manager run.
+; CHECK-O-NEXT: Running pass: IndVarSimplifyPass
+; CHECK-O-NEXT: Running pass: LoopIdiomRecognizePass
+; CHECK-O-NEXT: Running pass: LoopDeletionPass
+; CHECK-O-NEXT: Running pass: LoopUnrollPass
 ; CHECK-O-NEXT: Finished Loop pass manager run.
 ; CHECK-Os-NEXT: Running pass: MergedLoadStoreMotionPass
 ; CHECK-Os-NEXT: Running pass: GVN
 ; CHECK-Oz-NEXT: Running pass: MergedLoadStoreMotionPass
 ; CHECK-Oz-NEXT: Running pass: GVN
 ; CHECK-O2-NEXT: Running pass: MergedLoadStoreMotionPass
 ; CHECK-O2-NEXT: Running pass: GVN
 ; CHECK-O3-NEXT: Running pass: MergedLoadStoreMotionPass
 ; CHECK-O3-NEXT: Running pass: GVN
 ; CHECK-O-NEXT: Running pass: MemCpyOptPass
 ; CHECK-O-NEXT: Running pass: SCCPPass
 ; CHECK-O-NEXT: Running pass: BDCEPass
 ; CHECK-O-NEXT: Running analysis: DemandedBitsAnalysis
 ; CHECK-O-NEXT: Running pass: InstCombinePass
 ; CHECK-O-NEXT: Running pass: JumpThreadingPass
 ; CHECK-O-NEXT: Running pass: CorrelatedValuePropagationPass
 ; CHECK-O-NEXT: Running pass: DSEPass
+; CHECK-O-NEXT: Running pass: FunctionToLoopPassAdaptor<{{.*}}LICMPass{{.*}}>
 ; CHECK-O-NEXT: Running pass: ADCEPass
 ; CHECK-O-NEXT: Running analysis: PostDominatorTreeAnalysis
 ; CHECK-O-NEXT: Running pass: SimplifyCFGPass
 ; CHECK-O-NEXT: Running pass: InstCombinePass
 ; CHECK-O-NEXT: Finished llvm::Function pass manager run.
 ; CHECK-O-NEXT: Finished CGSCC pass manager run.
 ; CHECK-O-NEXT: Running pass: EliminateAvailableExternallyPass
 ; CHECK-O-NEXT: Running pass: ReversePostOrderFunctionAttrsPass