[(new) Pass Manager] instantiate SimplifyCFG with the same options as the old PM

This is a recommit of r316869 which was speculatively reverted with r317444 and 
subsequently shown to not be the cause of PR35210. That crash should be fixed
after r318237.

Original commit message:

The old PM sets the options of what used to be known as "latesimplifycfg" on the
instantiation after the vectorizers have run, so that's what we'redoing here.

FWIW, there's a later SimplifyCFGPass instantiation in both PMs where we do not
set the "late" options. I'm not sure if that's intentional or not.

Differential Revision: https://reviews.llvm.org/D39407

llvm-svn: 318299

1 files changed, 7 insertions, 2 deletions

diff --git a/llvm/lib/Passes/PassBuilder.cpp b/llvm/lib/Passes/PassBuilder.cpp
index c9b4acfe3da..7235a885184 100644
--- a/llvm/lib/Passes/PassBuilder.cpp
+++ b/llvm/lib/Passes/PassBuilder.cpp
@@ -757,8 +757,13 @@ PassBuilder::buildModuleOptimizationPipeline(OptimizationLevel Level,
   // Optimize parallel scalar instruction chains into SIMD instructions.
   OptimizePM.addPass(SLPVectorizerPass());
 
-  // Cleanup after all of the vectorizers.
-  OptimizePM.addPass(SimplifyCFGPass());
+  // Cleanup after all of the vectorizers. Simplification passes like CVP and
+  // GVN, loop transforms, and others have already run, so it's now better to
+  // convert to more optimized IR using more aggressive simplify CFG options.
+  OptimizePM.addPass(SimplifyCFGPass(SimplifyCFGOptions().
+                                         forwardSwitchCondToPhi(true).
+                                         convertSwitchToLookupTable(true).
+                                         needCanonicalLoops(false)));
   OptimizePM.addPass(InstCombinePass());
 
   // Unroll small loops to hide loop backedge latency and saturate any parallel