[SimplifyCFG] Enabled hoisting late in LTO pipeline.

[fhahn]

Summary

bb7d3af1139c disabled hoisting in SimplifyCFG by default, but enabled it
late in the pipeline. But it appears as if the LTO pipelines got missed.

This patch adjusts the LTO pipelines to also enable hoisting in the
later stages.

Unfortunately there's no easy way to add a test for the change I think.

[lebedev.ri]

Definitely makes sense to me.
Is this changing only the old-pm?

[fhahn]

In D93684#2467703, @lebedev.ri wrote:

Definitely makes sense to me.
Is this changing only the old-pm?

yeah, the first version just changed the legacy PM. I guess it makes sense for the new PM as well, although the pipeline looks quite different. Updated.

[fhahn]

ping :)

[lebedev.ri]

Looks good to me, thanks.

llvm/lib/Passes/PassBuilder.cpp

PassBuilder::buildLTODefaultPipeline(OptimizationLevel Level,
   MainFPM.addPass(DSEPass());
 
   // FIXME: at this point, we run a bunch of loop passes:
   // indVarSimplify, loopDeletion, loopInterchange, loopUnroll,
   // loopVectorize. Enable them once the remaining issue with LPM
   // are sorted out.
 
   MainFPM.addPass(InstCombinePass());
-  MainFPM.addPass(SimplifyCFGPass());
+  MainFPM.addPass(SimplifyCFGPass(SimplifyCFGOptions().hoistCommonInsts(true)));
   MainFPM.addPass(SCCPPass());
   MainFPM.addPass(InstCombinePass());
   MainFPM.addPass(BDCEPass());
 
   // FIXME: We may want to run SLPVectorizer here.
   // After vectorization, assume intrinsics may tell us more
   // about pointer alignments.
 #if 0
#endif
 
   // Enable splitting late in the FullLTO post-link pipeline. This is done in
   // the same stage in the old pass manager (\ref addLateLTOOptimizationPasses).
   if (EnableHotColdSplit)
     MPM.addPass(HotColdSplittingPass());
 
   // Add late LTO optimization passes.
   // Delete basic blocks, which optimization passes may have killed.
-  MPM.addPass(createModuleToFunctionPassAdaptor(SimplifyCFGPass()));
+  MPM.addPass(createModuleToFunctionPassAdaptor(
+      SimplifyCFGPass(SimplifyCFGOptions().hoistCommonInsts(true))));
 
   // Drop bodies of available eternally objects to improve GlobalDCE.
   MPM.addPass(EliminateAvailableExternallyPass());
 
   // Now that we have optimized the program, discard unreachable functions.
   MPM.addPass(GlobalDCEPass());
 
   if (PTO.MergeFunctions)

llvm/lib/Transforms/IPO/PassManagerBuilder.cpp

PM.add(createLoopUnrollPass(OptLevel, DisableUnrollLoops,
                               ForgetAllSCEVInLoopUnroll));
 
   PM.add(createWarnMissedTransformationsPass());
 
   // Now that we've optimized loops (in particular loop induction variables),
   // we may have exposed more scalar opportunities. Run parts of the scalar
   // optimizer again at this point.
   PM.add(createInstructionCombiningPass()); // Initial cleanup
-  PM.add(createCFGSimplificationPass()); // if-convert
+  PM.add(createCFGSimplificationPass(SimplifyCFGOptions() // if-convert
+                                         .hoistCommonInsts(true)));
   PM.add(createSCCPPass()); // Propagate exposed constants
   PM.add(createInstructionCombiningPass()); // Clean up again
   PM.add(createBitTrackingDCEPass());
 
   // More scalar chains could be vectorized due to more alias information
   if (SLPVectorize)
     PM.add(createSLPVectorizerPass()); // Vectorize parallel scalar chains.
 

 void PassManagerBuilder::addLateLTOOptimizationPasses(
     legacy::PassManagerBase &PM) {
   // See comment in the new PM for justification of scheduling splitting at
   // this stage (\ref buildLTODefaultPipeline).
   if (EnableHotColdSplit)
     PM.add(createHotColdSplittingPass());
 
   // Delete basic blocks, which optimization passes may have killed.
-  PM.add(createCFGSimplificationPass());
+  PM.add(
+      createCFGSimplificationPass(SimplifyCFGOptions().hoistCommonInsts(true)));
 
   // Drop bodies of available externally objects to improve GlobalDCE.
   PM.add(createEliminateAvailableExternallyPass());
 
   // Now that we have optimized the program, discard unreachable functions.
   PM.add(createGlobalDCEPass());
 
   // FIXME: this is profitable (for compiler time) to do at -O0 too, but