[IfConversion] Hoist removeBranch calls out of if/else clauses [NFC]

[uabelho]

Summary

Also added a comment.

Pulled out of https://reviews.llvm.org/D34099.

llvm/trunk/lib/CodeGen/IfConversion.cpp

if (MRI->tracksLiveness()) {
     // predicated instructions.
     Redefs.addLiveIns(CvtMBB);
     Redefs.addLiveIns(NextMBB);
     // Compute a set of registers which must not be killed by instructions in
     // BB1: This is everything live-in to BB2.
     DontKill.addLiveIns(NextMBB);
   }
 
-  if (CvtMBB.pred_size() > 1) {
-    BBI.NonPredSize -= TII->removeBranch(*BBI.BB);
+  // Remove the branches from the entry so we can add the contents of the true
+  // block to it.
+
+  if (CvtMBB.pred_size() > 1) {
     // Copy instructions in the true block, predicate them, and add them to
     // the entry block.
     CopyAndPredicateBlock(BBI, *CvtBBI, Cond);
 
     // RemoveExtraEdges won't work if the block has an unanalyzable branch, so
     // explicitly remove CvtBBI as a successor.
     BBI.BB->removeSuccessor(&CvtMBB, true);
   } else {
+    // Predicate the instructions in the true block.
     RemoveKills(CvtMBB.begin(), CvtMBB.end(), DontKill, *TRI);
     PredicateBlock(*CvtBBI, CvtMBB.end(), Cond);
 
     // Merge converted block into entry block.
-    BBI.NonPredSize -= TII->removeBranch(*BBI.BB);
     MergeBlocks(BBI, *CvtBBI);
   }
 
   bool IterIfcvt = true;
   if (!canFallThroughTo(*BBI.BB, NextMBB)) {
     InsertUncondBranch(*BBI.BB, NextMBB, TII);
     BBI.HasFallThrough = false;
     // Now ifcvt'd block will look like this:
bool IfConverter::IfConvertTriangle(BBInfo &BBI, IfcvtKind Kind) {
   if (HasEarlyExit) {
     // Get probabilities before modifying CvtMBB and BBI.BB.
     CvtNext = MBPI->getEdgeProbability(&CvtMBB, &NextMBB);
     CvtFalse = MBPI->getEdgeProbability(&CvtMBB, CvtBBI->FalseBB);
     BBNext = MBPI->getEdgeProbability(BBI.BB, &NextMBB);
     BBCvt = MBPI->getEdgeProbability(BBI.BB, &CvtMBB);
   }
 
-  if (CvtMBB.pred_size() > 1) {
-    BBI.NonPredSize -= TII->removeBranch(*BBI.BB);
+  // Remove the branches from the entry so we can add the contents of the true
+  // block to it.
+
+  if (CvtMBB.pred_size() > 1) {
     // Copy instructions in the true block, predicate them, and add them to
     // the entry block.
     CopyAndPredicateBlock(BBI, *CvtBBI, Cond, true);
 
     // RemoveExtraEdges won't work if the block has an unanalyzable branch, so
     // explicitly remove CvtBBI as a successor.
     BBI.BB->removeSuccessor(&CvtMBB, true);
   } else {
     // Predicate the 'true' block after removing its branch.
     CvtBBI->NonPredSize -= TII->removeBranch(CvtMBB);
     PredicateBlock(*CvtBBI, CvtMBB.end(), Cond);
 
     // Now merge the entry of the triangle with the true block.
-    BBI.NonPredSize -= TII->removeBranch(*BBI.BB);
     MergeBlocks(BBI, *CvtBBI, false);
   }
 
   // If 'true' block has a 'false' successor, add an exit branch to it.
   if (HasEarlyExit) {
     SmallVector<MachineOperand, 4> RevCond(CvtBBI->BrCond.begin(),
                                            CvtBBI->BrCond.end());
     if (TII->reverseBranchCondition(RevCond))