[PATCH] D30333: Split SimplifyCFG to run obscuring switch transforms only during last phase

[Mehdi AMINI via Phabricator via llvm-commits]

mehdi_amini added inline comments.


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Comment at: lib/Transforms/IPO/PassManagerBuilder.cpp:622
   addExtensionsToPM(EP_Peephole, MPM);
-  MPM.add(createCFGSimplificationPass());
+  MPM.add(createLateCFGSimplificationPass()); // Switches to lookup tables
   addInstructionCombiningPass(MPM);
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The comment is misleading, it seems that the only reason we run the pass here is for this purpose.


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Comment at: lib/Transforms/Scalar/SimplifyCFGPass.cpp:256
+  }
+};
 }
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Why two passes instead of a parameter?


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Comment at: lib/Transforms/Utils/SimplifyCFG.cpp:173
   SmallPtrSetImpl<BasicBlock *> *LoopHeaders;
+  bool LateSimplifyCFG;
   Value *isValueEqualityComparison(TerminatorInst *TI);
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Document.



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Comment at: lib/Transforms/Utils/SimplifyCFG.cpp:5568
 
-  if (SwitchToLookupTable(SI, Builder, DL, TTI))
+  if (LateSimplifyCFG && SwitchToLookupTable(SI, Builder, DL, TTI))
     return SimplifyCFG(BB, TTI, BonusInstThreshold, AC) | true;
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Comment.


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Comment at: lib/Transforms/Utils/SimplifyCFG.cpp:6024
 /// of the CFG.  It returns true if a modification was made.
 ///
 bool llvm::SimplifyCFG(BasicBlock *BB, const TargetTransformInfo &TTI,
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Document the parameter in the doxygen.


https://reviews.llvm.org/D30333