[BranchFolding] Remove what appears to be dead code

[craig.topper]

Summary

This code tries to handle the case where IBB is an EHPad, but there's an earlier check that uses PBB->hasEHPadSuccessor(). Where PBB is a predecessor of IBB. The hasEHPadSuccessor function would have visited IBB and seen that it was an EHPad and returned false. This would prevent us from reaching this code with IBB as an EHPad.

[craig.topper]

Ping

[rnk]

lgtm

Looks like this code was originally added in rL37427 (ancient) and made dead in rL143001.

llvm/trunk/lib/CodeGen/BranchFolding.cpp

for (MachineBasicBlock *PBB : I->predecessors()) {
           // This is the QBB case described above
           if (!FBB) {
             auto Next = ++PBB->getIterator();
             if (Next != MF.end())
               FBB = &*Next;
           }
         }
 
-        // Failing case: the only way IBB can be reached from PBB is via
-        // exception handling.  Happens for landing pads.  Would be nice to have
-        // a bit in the edge so we didn't have to do all this.
-        if (IBB->isEHPad()) {
-          MachineFunction::iterator IP = ++PBB->getIterator();
-          MachineBasicBlock *PredNextBB = nullptr;
-          if (IP != MF.end())
-            PredNextBB = &*IP;
-          if (!TBB) {
-            if (IBB != PredNextBB)      // fallthrough
-              continue;
-          } else if (FBB) {
-            if (TBB != IBB && FBB != IBB)   // cbr then ubr
-              continue;
-          } else if (Cond.empty()) {
-            if (TBB != IBB)               // ubr
-              continue;
-          } else {
-            if (TBB != IBB && IBB != PredNextBB)  // cbr
-              continue;
-          }
-        }
-
         // Remove the unconditional branch at the end, if any.
         if (TBB && (Cond.empty() || FBB)) {
           DebugLoc dl = PBB->findBranchDebugLoc();
           TII->removeBranch(*PBB);
           if (!Cond.empty())
             // reinsert conditional branch only, for now
             TII->insertBranch(*PBB, (TBB == IBB) ? FBB : TBB, nullptr,
                               NewCond, dl);