[JumpThreading] Remove extraneous calls to setEdgeProbability

[kazu]

Summary

This patch removes extraneous calls to setEdgeProbability introduced
in c91487769d80487eba1712a7a172a1c8977a9b4f.

The follow-up patch, a7b662d0f4098371b96ce4446fb0eba79b0b649f, has
since fixed BranchProbabilityInfo::eraseBlock, so we don't need to
worry about getting stale values from getEdgeProbability.

Also, since getEdgeProbability(BB, BB->getSingleSuccessor()) returns
edge probability 1/1 by default for BB with exactly one successor
edge, we don't need to explicitly call setEdgeProbability.

This patch introduces almost no functional change, but we do end up
reducing debug messages from setEdgeProbability.

[MaskRay]

Should thread-prob-3.ll be renumbered?

LGTM but I hope other reviews can confirm.

[kazu]

In D90284#2358163, @MaskRay wrote:

Should thread-prob-3.ll be renumbered?

LGTM but I hope other reviews can confirm.

Thank you for the review. Yes, I am going to rename thread-prob-3.ll in a separate patch.

llvm/lib/Transforms/Scalar/JumpThreading.cpp

for (auto NewBB : NewBBs) {
     BlockFrequency NewBBFreq(0);
     Updates.push_back({DominatorTree::Insert, NewBB, BB});
     for (auto Pred : predecessors(NewBB)) {
       Updates.push_back({DominatorTree::Delete, Pred, BB});
       Updates.push_back({DominatorTree::Insert, Pred, NewBB});
       if (HasProfileData) // Update frequencies between Pred -> NewBB.
         NewBBFreq += FreqMap.lookup(Pred);
     }
-    if (HasProfileData) {
-      // Apply the summed frequency to NewBB.
+    if (HasProfileData) // Apply the summed frequency to NewBB.
       BFI->setBlockFreq(NewBB, NewBBFreq.getFrequency());
-
-      // NewBB has exactly one successor.
-      SmallVector<BranchProbability, 1> BBSuccProbs;
-      BBSuccProbs.push_back(BranchProbability::getOne());
-      BPI->setEdgeProbability(NewBB, BBSuccProbs);
-    }
   }
 
   DTU->applyUpdatesPermissive(Updates);
   return NewBBs[0];
 }
 
 bool JumpThreadingPass::doesBlockHaveProfileData(BasicBlock *BB) {
   const Instruction *TI = BB->getTerminator();
else {
     // Normalize edge probabilities so that they sum up to one.
     BranchProbability::normalizeProbabilities(BBSuccProbs.begin(),
                                               BBSuccProbs.end());
   }
 
   // Update edge probabilities in BPI.
   BPI->setEdgeProbability(BB, BBSuccProbs);
 
-  // NewBB has exactly one successor.
-  SmallVector<BranchProbability, 1> NewBBSuccProbs;
-  NewBBSuccProbs.push_back(BranchProbability::getOne());
-  BPI->setEdgeProbability(NewBB, NewBBSuccProbs);
-
   // Update the profile metadata as well.
   //
   // Don't do this if the profile of the transformed blocks was statically
   // estimated.  (This could occur despite the function having an entry
   // frequency in completely cold parts of the CFG.)
   //
   // In this case we don't want to suggest to subsequent passes that the
   // calculated weights are fully consistent.  Consider this graph:
void JumpThreadingPass::UnfoldSelectInstr(BasicBlock *Pred, BasicBlock *BB,
   DTU->applyUpdatesPermissive({{DominatorTree::Insert, NewBB, BB},
                                {DominatorTree::Insert, Pred, NewBB}});
 
   // Update any other PHI nodes in BB.
   for (BasicBlock::iterator BI = BB->begin();
        PHINode *Phi = dyn_cast<PHINode>(BI); ++BI)
     if (Phi != SIUse)
       Phi->addIncoming(Phi->getIncomingValueForBlock(Pred), NewBB);
-
-  if (HasProfileData) {
-    // NewBB has exactly one successor.
-    SmallVector<BranchProbability, 1> BBSuccProbs;
-    BBSuccProbs.push_back(BranchProbability::getOne());
-    BPI->setEdgeProbability(NewBB, BBSuccProbs);
-  }
 }
 
 bool JumpThreadingPass::TryToUnfoldSelect(SwitchInst *SI, BasicBlock *BB) {
   PHINode *CondPHI = dyn_cast<PHINode>(SI->getCondition());
 
   if (!CondPHI || CondPHI->getParent() != BB)
     return false;
 

llvm/test/Transforms/JumpThreading/thread-prob-1.ll

-; RUN: opt -debug-only=branch-prob -jump-threading -S %s 2>&1 | FileCheck %s
-
-; Make sure that we set the branch probability for the newly created
-; basic block.
-
-define void @foo(i1 %arg1, i1 %arg2, i32 %arg3) !prof !0 !PGOFuncName !1 {
-entry:
-  call void @bar(i32 0)
-  br i1 %arg1, label %bb3, label %bb1, !prof !2
-
-bb1:
-  call void @bar(i32 1)
-  br i1 %arg2, label %bb2, label %bb3, !prof !3
-
-bb2:
-  call void @bar(i32 2)
-  br label %bb3
-
-bb3:
-; CHECK: set edge bb3.thr_comm -> 0 successor probability to 0x80000000 / 0x80000000
-%ptr = phi i32 [ 0, %bb1 ], [ 0, %entry ], [ %arg3, %bb2 ]
-  call void @bar(i32 3)
-  %bool = icmp eq i32 %ptr, 0
-  br i1 %bool, label %exit, label %bb4, !prof !4
-; CHECK: set edge bb3.thread -> 0 successor probability to 0x80000000 / 0x80000000
-
-bb4:
-  call void @bar(i32 %ptr)
-  br label %exit
-
-exit:
-  ret void
-}
-
-declare void @bar(i32)
-
-!0 = !{!"function_entry_count", i64 15985}
-!1 = !{!"foo:foo"}
-!2 = !{!"branch_weights", i32 15973, i32 36865}
-!3 = !{!"branch_weights", i32 2957, i32 5798}
-!4 = !{!"branch_weights", i32 1807, i32 35058}
-!5 = !{!"branch_weights", i32 38, i32 287958}

llvm/test/Transforms/JumpThreading/thread-prob-2.ll

-; RUN: opt -debug-only=branch-prob -jump-threading -S %s 2>&1 | FileCheck %s
-
-; Make sure that we set the branch probability for the newly created
-; basic block.
-
-define void @foo(i32 %v0, i1 %arg2) !prof !0 !PGOFuncName !1 {
-entry:
-  %bool1 = icmp eq i32 %v0, 0
-  br i1 %bool1, label %bb2, label %bb1, !prof !2
-
-bb1:
-  %sel = select i1 %arg2, i32 %v0, i32 0, !prof !3
-  br label %bb2
-; CHECK: set edge select.unfold -> 0 successor probability to 0x80000000 / 0x80000000
-
-bb2:
-  %phi = phi i32 [ %sel, %bb1 ], [ 0, %entry ]
-  %bool2 = icmp eq i32 %phi, 0
-  br i1 %bool2, label %exit, label %bb3, !prof !4
-
-bb3:
-  br label %exit
-
-exit:
-  ret void
-}
-
-!0 = !{!"function_entry_count", i64 15985}
-!1 = !{!"foo.cpp:foo"}
-!2 = !{!"branch_weights", i32 0, i32 36865}
-!3 = !{!"branch_weights", i32 35058, i32 1807}
-!4 = !{!"branch_weights", i32 1807, i32 35058}