[LateJumpThreading] Enable LateJumpThreading right before CGP.

[kparzysz]

lib/CodeGen/TargetPassConfig.cpp

669

That should be under "opt level != none".

[bmakam]

Address Krzysztof's comment.

[craig.topper]

What's going on with this patch? We also saw a performance regression on one of our benchmarks. And I was interested in whether this woudl help.

[bmakam]

In D37866#882728, @craig.topper wrote:

What's going on with this patch? We also saw a performance regression on one of our benchmarks. And I was interested in whether this woudl help.

Have you tested it? Could you share your results if it fixed the regression? I have only tested it on the benchmark that regressed for us and it recovered the regression, but need to test some more.

[bmakam]

D42260 seems a better fix to this regression.

lib/CodeGen/CodeGenPrepare.cpp

 #include "llvm/Support/Debug.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/MathExtras.h"
 #include "llvm/Support/raw_ostream.h"
 #include "llvm/Target/TargetLowering.h"
 #include "llvm/Target/TargetMachine.h"
 #include "llvm/Target/TargetOptions.h"
 #include "llvm/Target/TargetSubtargetInfo.h"
+#include "llvm/Transforms/Scalar.h"
 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
 #include "llvm/Transforms/Utils/BypassSlowDivision.h"
 #include "llvm/Transforms/Utils/Cloning.h"
 #include "llvm/Transforms/Utils/Local.h"
 #include "llvm/Transforms/Utils/SimplifyLibCalls.h"
 #include "llvm/Transforms/Utils/ValueMapper.h"
 #include <algorithm>
 #include <cassert>
public:
     StringRef getPassName() const override { return "CodeGen Prepare"; }
 
     void getAnalysisUsage(AnalysisUsage &AU) const override {
       // FIXME: When we can selectively preserve passes, preserve the domtree.
       AU.addRequired<ProfileSummaryInfoWrapperPass>();
       AU.addRequired<TargetLibraryInfoWrapperPass>();
       AU.addRequired<TargetTransformInfoWrapperPass>();
       AU.addRequired<LoopInfoWrapperPass>();
+      AU.addRequiredID(LoopSimplifyID);
     }
 
   private:
     bool eliminateFallThrough(Function &F);
     bool eliminateMostlyEmptyBlocks(Function &F);
     BasicBlock *findDestBlockOfMergeableEmptyBlock(BasicBlock *BB);
     bool canMergeBlocks(const BasicBlock *BB, const BasicBlock *DestBB) const;
     void eliminateMostlyEmptyBlock(BasicBlock *BB);
class TypePromotionTransaction;
   };
 
 } // end anonymous namespace
 
 char CodeGenPrepare::ID = 0;
 
 INITIALIZE_PASS_BEGIN(CodeGenPrepare, DEBUG_TYPE,
                       "Optimize for code generation", false, false)
+INITIALIZE_PASS_DEPENDENCY(LoopSimplify)
 INITIALIZE_PASS_DEPENDENCY(ProfileSummaryInfoWrapperPass)
 INITIALIZE_PASS_END(CodeGenPrepare, DEBUG_TYPE,
                     "Optimize for code generation", false, false)
 
 FunctionPass *llvm::createCodeGenPreparePass() { return new CodeGenPrepare(); }
 
 bool CodeGenPrepare::runOnFunction(Function &F) {
   if (skipFunction(F))

lib/CodeGen/TargetPassConfig.cpp

static cl::opt<bool> DisablePostRAMachineLICM("disable-postra-machine-licm",
     cl::Hidden,
     cl::desc("Disable Machine LICM"));
 static cl::opt<bool> DisableMachineSink("disable-machine-sink", cl::Hidden,
     cl::desc("Disable Machine Sinking"));
 static cl::opt<bool> DisableLSR("disable-lsr", cl::Hidden,
     cl::desc("Disable Loop Strength Reduction Pass"));
 static cl::opt<bool> DisableConstantHoisting("disable-constant-hoisting",
     cl::Hidden, cl::desc("Disable ConstantHoisting"));
+static cl::opt<bool> DisableLateJumpThreading("disable-late-jt", cl::Hidden,
+    cl::desc("Disable Late Jump Threading"));
 static cl::opt<bool> DisableCGP("disable-cgp", cl::Hidden,
     cl::desc("Disable Codegen Prepare"));
 static cl::opt<bool> DisableCopyProp("disable-copyprop", cl::Hidden,
     cl::desc("Disable Copy Propagation pass"));
 static cl::opt<bool> DisablePartialLibcallInlining("disable-partial-libcall-inlining",
     cl::Hidden, cl::desc("Disable Partial Libcall Inlining"));
 static cl::opt<bool> EnableImplicitNullChecks(
     "enable-implicit-null-checks",
case ExceptionHandling::None:
     addPass(createUnreachableBlockEliminationPass());
     break;
   }
 }
 
 /// Add pass to prepare the LLVM IR for code generation. This should be done
 /// before exception handling preparation passes.
 void TargetPassConfig::addCodeGenPrepare() {
+  if (getOptLevel() != CodeGenOpt::None && !DisableLateJumpThreading)
+    addPass(createLateJumpThreadingPass());
   if (getOptLevel() != CodeGenOpt::None && !DisableCGP)
     addPass(createCodeGenPreparePass());
   addPass(createRewriteSymbolsPass());
 }
 
 /// Add common passes that perform LLVM IR to IR transforms in preparation for
 /// instruction selection.
 void TargetPassConfig::addISelPrepare() {