X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=lib%2FCodeGen%2FBranchFolding.cpp;h=8f519407ccd4e8c2890557861ab47989c01bf207;hb=22772214de79aa1c5ca38c4fb1da137d8fb30a05;hp=7e27bf5631eb2ca0c77d84f2119d95c376ae3cee;hpb=2cd9ffef6e74febd727f0b548c21ba3f4e5cd26f;p=oota-llvm.git

diff --git a/lib/CodeGen/BranchFolding.cpp b/lib/CodeGen/BranchFolding.cpp
index 7e27bf5631e..8f519407ccd 100644
--- a/lib/CodeGen/BranchFolding.cpp
+++ b/lib/CodeGen/BranchFolding.cpp
@@ -105,17 +105,6 @@ void BranchFolder::RemoveDeadBlock(MachineBasicBlock *MBB) {
   while (!MBB->succ_empty())
     MBB->removeSuccessor(MBB->succ_end()-1);
 
-  // If there are any labels in the basic block, unregister them from
-  // MachineModuleInfo.
-  if (MMI && !MBB->empty()) {
-    for (MachineBasicBlock::iterator I = MBB->begin(), E = MBB->end();
-         I != E; ++I) {
-      if (I->isLabel())
-        // The label ID # is always operand #0, an immediate.
-        MMI->InvalidateLabel(I->getOperand(0).getImm());
-    }
-  }
-
   // Remove the block.
   MF->erase(MBB);
 }
@@ -203,7 +192,7 @@ bool BranchFolder::OptimizeFunction(MachineFunction &MF,
     MadeChange |= MadeChangeThisIteration;
   }
 
-  // See if any jump tables have become mergable or dead as the code generator
+  // See if any jump tables have become dead as the code generator
   // did its thing.
   MachineJumpTableInfo *JTI = MF.getJumpTableInfo();
   if (JTI == 0) {
@@ -211,27 +200,8 @@ bool BranchFolder::OptimizeFunction(MachineFunction &MF,
     return MadeChange;
   }
   
-  const std::vector<MachineJumpTableEntry> &JTs = JTI->getJumpTables();
-  // Figure out how these jump tables should be merged.
-  std::vector<unsigned> JTMapping;
-  JTMapping.reserve(JTs.size());
-
-  // We always keep the 0th jump table.
-  JTMapping.push_back(0);
-
-  // Scan the jump tables, seeing if there are any duplicates.  Note that this
-  // is N^2, which should be fixed someday.
-  for (unsigned i = 1, e = JTs.size(); i != e; ++i) {
-    if (JTs[i].MBBs.empty())
-      JTMapping.push_back(i);
-    else
-      JTMapping.push_back(JTI->getJumpTableIndex(JTs[i].MBBs));
-  }
-
-  // If a jump table was merge with another one, walk the function rewriting
-  // references to jump tables to reference the new JT ID's.  Keep track of
-  // whether we see a jump table idx, if not, we can delete the JT.
-  BitVector JTIsLive(JTs.size());
+  // Walk the function to find jump tables that are live.
+  BitVector JTIsLive(JTI->getJumpTables().size());
   for (MachineFunction::iterator BB = MF.begin(), E = MF.end();
        BB != E; ++BB) {
     for (MachineBasicBlock::iterator I = BB->begin(), E = BB->end();
@@ -239,17 +209,14 @@ bool BranchFolder::OptimizeFunction(MachineFunction &MF,
       for (unsigned op = 0, e = I->getNumOperands(); op != e; ++op) {
         MachineOperand &Op = I->getOperand(op);
         if (!Op.isJTI()) continue;
-        unsigned NewIdx = JTMapping[Op.getIndex()];
-        Op.setIndex(NewIdx);
 
         // Remember that this JT is live.
-        JTIsLive.set(NewIdx);
+        JTIsLive.set(Op.getIndex());
       }
   }
 
-  // Finally, remove dead jump tables.  This happens either because the
-  // indirect jump was unreachable (and thus deleted) or because the jump
-  // table was merged with some other one.
+  // Finally, remove dead jump tables.  This happens when the
+  // indirect jump was unreachable (and thus deleted).
   for (unsigned i = 0, e = JTIsLive.size(); i != e; ++i)
     if (!JTIsLive.test(i)) {
       JTI->RemoveJumpTable(i);
@@ -1005,15 +972,21 @@ static bool IsBetterFallthrough(MachineBasicBlock *MBB1,
   // MBB1 doesn't, we prefer to fall through into MBB1.  This allows us to
   // optimize branches that branch to either a return block or an assert block
   // into a fallthrough to the return.
-  if (MBB1->empty() || MBB2->empty()) return false;
+  if (IsEmptyBlock(MBB1) || IsEmptyBlock(MBB2)) return false;
 
   // If there is a clear successor ordering we make sure that one block
   // will fall through to the next
   if (MBB1->isSuccessor(MBB2)) return true;
   if (MBB2->isSuccessor(MBB1)) return false;
 
-  MachineInstr *MBB1I = --MBB1->end();
-  MachineInstr *MBB2I = --MBB2->end();
+  // Neither block consists entirely of debug info (per IsEmptyBlock check),
+  // so we needn't test for falling off the beginning here.
+  MachineBasicBlock::iterator MBB1I = --MBB1->end();
+  while (MBB1I->isDebugValue())
+    --MBB1I;
+  MachineBasicBlock::iterator MBB2I = --MBB2->end();
+  while (MBB2I->isDebugValue())
+    --MBB2I;
   return MBB2I->getDesc().isCall() && !MBB1I->getDesc().isCall();
 }
 
@@ -1154,22 +1127,6 @@ ReoptimizeBlock:
           !IsBetterFallthrough(PriorTBB, MBB))
         DoTransform = false;
 
-      // We don't want to do this transformation if we have control flow like:
-      //   br cond BB2
-      // BB1:
-      //   ..
-      //   jmp BBX
-      // BB2:
-      //   ..
-      //   ret
-      //
-      // In this case, we could actually be moving the return block *into* a
-      // loop!
-      if (DoTransform && !MBB->succ_empty() &&
-          (!PriorTBB->canFallThrough() || PriorTBB->empty()))
-        DoTransform = false;
-
-
       if (DoTransform) {
         // Reverse the branch so we will fall through on the previous true cond.
         SmallVector<MachineOperand, 4> NewPriorCond(PriorCond);