[PM] Enable the new simple loop unswitch pass in the new pass manager

(where it is the only realistic option).

This passes the LLVM test suite for me, but I'm clearly still hammering
on this.

llvm-svn: 303952

llvm/lib/Passes/PassBuilder.cpp

@@ -341,10 +341,7 @@ PassBuilder::buildFunctionSimplificationPipeline(OptimizationLevel Level,
   // 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
+  LPM1.addPass(SimpleLoopUnswitchPass());
   LPM2.addPass(IndVarSimplifyPass());
   LPM2.addPass(LoopIdiomRecognizePass());
   LPM2.addPass(LoopDeletionPass());

llvm/test/Other/new-pm-defaults.ll

@@ -95,6 +95,7 @@
 ; CHECK-O-NEXT: Running pass: LoopRotatePass
 ; CHECK-O-NEXT: Running pass: LICM
 ; CHECK-O-NEXT: Running analysis: OuterAnalysisManagerProxy
+; CHECK-O-NEXT: Running pass: SimpleLoopUnswitchPass
 ; CHECK-O-NEXT: Finished Loop pass manager run.
 ; CHECK-O-NEXT: Running pass: SimplifyCFGPass
 ; CHECK-O-NEXT: Running pass: InstCombinePass