Patch #7 from Saem:

[oota-llvm.git] / lib / VMCore / BasicBlock.cpp

diff --git a/lib/VMCore/BasicBlock.cpp b/lib/VMCore/BasicBlock.cpp
index 95eab23edff4b07e74cb341bcfb00e6512564f95..ab7798c3866e91a82b673516ce7ea2af587114d6 100644 (file)
--- a/lib/VMCore/BasicBlock.cpp
+++ b/lib/VMCore/BasicBlock.cpp
@@ -1,10 +1,10 @@
 //===-- BasicBlock.cpp - Implement BasicBlock related methods -------------===//
-// 
+//
 //                     The LLVM Compiler Infrastructure
 //
 // This file was developed by the LLVM research group and is distributed under
 // the University of Illinois Open Source License. See LICENSE.TXT for details.
-// 
+//
 //===----------------------------------------------------------------------===//
 //
 // This file implements the BasicBlock class for the VMCore library.
@@ -102,6 +102,14 @@ void BasicBlock::eraseFromParent() {
   getParent()->getBasicBlockList().erase(this);
 }
 
+/// moveBefore - Unlink this instruction from its current function and
+/// insert it into the function that MovePos lives in, right before
+/// MovePos.
+void BasicBlock::moveBefore(BasicBlock *MovePos) {
+  MovePos->getParent()->getBasicBlockList().splice(MovePos,
+                       getParent()->getBasicBlockList(), this);
+}
+
 
 TerminatorInst *BasicBlock::getTerminator() {
   if (InstList.empty()) return 0;
@@ -128,17 +136,17 @@ BasicBlock *BasicBlock::getSinglePredecessor() {
   return (PI == E) ? ThePred : 0 /*multiple preds*/;
 }
 
-// removePredecessor - This method is used to notify a BasicBlock that the
-// specified Predecessor of the block is no longer able to reach it.  This is
-// actually not used to update the Predecessor list, but is actually used to 
-// update the PHI nodes that reside in the block.  Note that this should be
-// called while the predecessor still refers to this block.
-//
+/// removePredecessor - This method is used to notify a BasicBlock that the
+/// specified Predecessor of the block is no longer able to reach it.  This is
+/// actually not used to update the Predecessor list, but is actually used to
+/// update the PHI nodes that reside in the block.  Note that this should be
+/// called while the predecessor still refers to this block.
+///
 void BasicBlock::removePredecessor(BasicBlock *Pred,
                                    bool DontDeleteUselessPHIs) {
   assert((hasNUsesOrMore(16)||// Reduce cost of this assertion for complex CFGs.
           find(pred_begin(this), pred_end(this), Pred) != pred_end(this)) &&
-        "removePredecessor: BB is not a predecessor!");
+         "removePredecessor: BB is not a predecessor!");
 
   if (InstList.empty()) return;
   PHINode *APN = dyn_cast<PHINode>(&front());
@@ -153,9 +161,9 @@ void BasicBlock::removePredecessor(BasicBlock *Pred,
   //    br Loop                 ;; %x2 does not dominate all uses
   //
   // This is because the PHI node input is actually taken from the predecessor
-  // basic block.  The only case this can happen is with a self loop, so we 
+  // basic block.  The only case this can happen is with a self loop, so we
   // check for this case explicitly now.
-  // 
+  //
   unsigned max_idx = APN->getNumIncomingValues();
   assert(max_idx != 0 && "PHI Node in block with 0 predecessors!?!?!");
   if (max_idx == 2) {
@@ -189,27 +197,35 @@ void BasicBlock::removePredecessor(BasicBlock *Pred,
     // Okay, now we know that we need to remove predecessor #pred_idx from all
     // PHI nodes.  Iterate over each PHI node fixing them up
     PHINode *PN;
-    for (iterator II = begin(); (PN = dyn_cast<PHINode>(II)); ++II)
+    for (iterator II = begin(); (PN = dyn_cast<PHINode>(II)); ) {
+      ++II;
       PN->removeIncomingValue(Pred, false);
+      // If all incoming values to the Phi are the same, we can replace the Phi
+      // with that value.
+      if (Value *PNV = PN->hasConstantValue()) {
+        PN->replaceAllUsesWith(PNV);
+        PN->eraseFromParent();
+      }
+    }
   }
 }
 
 
-// splitBasicBlock - This splits a basic block into two at the specified
-// instruction.  Note that all instructions BEFORE the specified iterator stay
-// as part of the original basic block, an unconditional branch is added to 
-// the new BB, and the rest of the instructions in the BB are moved to the new
-// BB, including the old terminator.  This invalidates the iterator.
-//
-// Note that this only works on well formed basic blocks (must have a 
-// terminator), and 'I' must not be the end of instruction list (which would
-// cause a degenerate basic block to be formed, having a terminator inside of
-// the basic block). 
-//
+/// splitBasicBlock - This splits a basic block into two at the specified
+/// instruction.  Note that all instructions BEFORE the specified iterator stay
+/// as part of the original basic block, an unconditional branch is added to
+/// the new BB, and the rest of the instructions in the BB are moved to the new
+/// BB, including the old terminator.  This invalidates the iterator.
+///
+/// Note that this only works on well formed basic blocks (must have a
+/// terminator), and 'I' must not be the end of instruction list (which would
+/// cause a degenerate basic block to be formed, having a terminator inside of
+/// the basic block).
+///
 BasicBlock *BasicBlock::splitBasicBlock(iterator I, const std::string &BBName) {
   assert(getTerminator() && "Can't use splitBasicBlock on degenerate BB!");
-  assert(I != InstList.end() && 
-        "Trying to get me to create degenerate basic block!");
+  assert(I != InstList.end() &&
+         "Trying to get me to create degenerate basic block!");
 
   BasicBlock *New = new BasicBlock(BBName, getParent(), getNext());