[llvm-commits] [llvm] r53735 - /llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp

[Owen Anderson]

Author: resistor
Date: Thu Jul 17 15:00:46 2008
New Revision: 53735

URL: http://llvm.org/viewvc/llvm-project?rev=53735&view=rev
Log:
Use MergeBlockIntoPredecessor to simplify some code.

Modified:
    llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp

Modified: llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp?rev=53735&r1=53734&r2=53735&view=diff

==============================================================================
--- llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp (original)
+++ llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp Thu Jul 17 15:00:46 2008
@@ -2036,6 +2036,12 @@
   // pred, and if there is only one distinct successor of the predecessor, and
   // if there are no PHI nodes.
   //
+  if (MergeBlockIntoPredecessor(BB))
+    return true;
+
+  // Otherwise, if this block only has a single predecessor, and if that block
+  // is a conditional branch, see if we can hoist any code from this block up
+  // into our predecessor.
   pred_iterator PI(pred_begin(BB)), PE(pred_end(BB));
   BasicBlock *OnlyPred = *PI++;
   for (; PI != PE; ++PI)  // Search all predecessors, see if they are all same
@@ -2043,57 +2049,7 @@
       OnlyPred = 0;       // There are multiple different predecessors...
       break;
     }
-
-  BasicBlock *OnlySucc = 0;
-  if (OnlyPred && OnlyPred != BB &&    // Don't break self loops
-      OnlyPred->getTerminator()->getOpcode() != Instruction::Invoke) {
-    // Check to see if there is only one distinct successor...
-    succ_iterator SI(succ_begin(OnlyPred)), SE(succ_end(OnlyPred));
-    OnlySucc = BB;
-    for (; SI != SE; ++SI)
-      if (*SI != OnlySucc) {
-        OnlySucc = 0;     // There are multiple distinct successors!
-        break;
-      }
-  }
-
-  if (OnlySucc) {
-    DOUT << "Merging: " << *BB << "into: " << *OnlyPred;
-
-    // Resolve any PHI nodes at the start of the block.  They are all
-    // guaranteed to have exactly one entry if they exist, unless there are
-    // multiple duplicate (but guaranteed to be equal) entries for the
-    // incoming edges.  This occurs when there are multiple edges from
-    // OnlyPred to OnlySucc.
-    //
-    while (PHINode *PN = dyn_cast<PHINode>(&BB->front())) {
-      PN->replaceAllUsesWith(PN->getIncomingValue(0));
-      BB->getInstList().pop_front();  // Delete the phi node.
-    }
-
-    // Delete the unconditional branch from the predecessor.
-    OnlyPred->getInstList().pop_back();
-
-    // Move all definitions in the successor to the predecessor.
-    OnlyPred->getInstList().splice(OnlyPred->end(), BB->getInstList());
-
-    // Make all PHI nodes that referred to BB now refer to Pred as their
-    // source.
-    BB->replaceAllUsesWith(OnlyPred);
-
-    // Inherit predecessors name if it exists.
-    if (!OnlyPred->hasName())
-      OnlyPred->takeName(BB);
-    
-    // Erase basic block from the function.
-    M->getBasicBlockList().erase(BB);
-
-    return true;
-  }
-
-  // Otherwise, if this block only has a single predecessor, and if that block
-  // is a conditional branch, see if we can hoist any code from this block up
-  // into our predecessor.
+  
   if (OnlyPred)
     if (BranchInst *BI = dyn_cast<BranchInst>(OnlyPred->getTerminator()))
       if (BI->isConditional()) {
@@ -2101,6 +2057,7 @@
         BasicBlock *OtherBB = BI->getSuccessor(BI->getSuccessor(0) == BB);
         PI = pred_begin(OtherBB);
         ++PI;
+        
         if (PI == pred_end(OtherBB)) {
           // We have a conditional branch to two blocks that are only reachable
           // from the condbr.  We know that the condbr dominates the two blocks,
@@ -2108,7 +2065,7 @@
           // blocks.  If so, we can hoist it up to the branching block.
           Changed |= HoistThenElseCodeToIf(BI);
         } else {
-          OnlySucc = NULL;
+          BasicBlock* OnlySucc = NULL;
           for (succ_iterator SI = succ_begin(BB), SE = succ_end(BB);
                SI != SE; ++SI) {
             if (!OnlySucc)