fix a really incorrect comment.

[oota-llvm.git] / include / llvm / Transforms / Utils / BasicBlockUtils.h

diff --git a/include/llvm/Transforms/Utils/BasicBlockUtils.h b/include/llvm/Transforms/Utils/BasicBlockUtils.h
index 92f35ccda41b1b765710ac6d37519008b444d8c3..6dd92dd71ff1e75bf0ef9ebf7511f4dab3e455b4 100644 (file)
--- a/include/llvm/Transforms/Utils/BasicBlockUtils.h
+++ b/include/llvm/Transforms/Utils/BasicBlockUtils.h
@@ -24,6 +24,15 @@ namespace llvm {
 
 class Instruction;
 class Pass;
+class AliasAnalysis;
+
+/// DeleteDeadBlock - Delete the specified block, which must have no
+/// predecessors.
+void DeleteDeadBlock(BasicBlock *BB);
+  
+/// MergeBlockIntoPredecessor - Attempts to merge a block into its predecessor,
+/// if possible.  The return value indicates success or failure.
+bool MergeBlockIntoPredecessor(BasicBlock* BB, Pass* P = 0);
 
 // ReplaceInstWithValue - Replace all uses of an instruction (specified by BI)
 // with a value, then remove and delete the original instruction.
@@ -43,6 +52,25 @@ void ReplaceInstWithInst(BasicBlock::InstListType &BIL,
 //
 void ReplaceInstWithInst(Instruction *From, Instruction *To);
 
+/// FindAvailableLoadedValue - Scan the ScanBB block backwards (starting at the
+/// instruction before ScanFrom) checking to see if we have the value at the
+/// memory address *Ptr locally available within a small number of instructions.
+/// If the value is available, return it.
+///
+/// If not, return the iterator for the last validated instruction that the 
+/// value would be live through.  If we scanned the entire block and didn't find
+/// something that invalidates *Ptr or provides it, ScanFrom would be left at
+/// begin() and this returns null.  ScanFrom could also be left 
+///
+/// MaxInstsToScan specifies the maximum instructions to scan in the block.  If
+/// it is set to 0, it will scan the whole block. You can also optionally
+/// specify an alias analysis implementation, which makes this more precise.
+Value *FindAvailableLoadedValue(Value *Ptr, BasicBlock *ScanBB,
+                                BasicBlock::iterator &ScanFrom,
+                                unsigned MaxInstsToScan = 6,
+                                AliasAnalysis *AA = 0);
+    
+  
 
 // RemoveSuccessor - Change the specified terminator instruction such that its
 // successor #SuccNum no longer exists.  Because this reduces the outgoing
@@ -61,13 +89,15 @@ bool isCriticalEdge(const TerminatorInst *TI, unsigned SuccNum,
                     bool AllowIdenticalEdges = false);
 
 /// SplitCriticalEdge - If this edge is a critical edge, insert a new node to
-/// split the critical edge.  This will update DominatorTree, and DominatorFrontier 
-/// information if it is available, thus calling this pass will not invalidate 
-/// either of them. This returns true if the edge was split, false otherwise.  
-/// If MergeIdenticalEdges is true (the default), *all* edges from TI to the 
+/// split the critical edge.  This will update DominatorTree and
+/// DominatorFrontier information if it is available, thus calling this pass
+/// will not invalidate either of them. This returns true if the edge was split,
+/// false otherwise.  
+///
+/// If MergeIdenticalEdges is true (not the default), *all* edges from TI to the
 /// specified successor will be merged into the same critical edge block.  
 /// This is most commonly interesting with switch instructions, which may 
-/// have many edges to any one destination.  This ensures that all edges to that 
+/// have many edges to any one destination.  This ensures that all edges to that
 /// dest go to one block instead of each going to a different block, but isn't 
 /// the standard definition of a "critical edge".
 ///
@@ -118,6 +148,19 @@ BasicBlock *SplitEdge(BasicBlock *From, BasicBlock *To, Pass *P);
 /// the loop info is updated.
 ///
 BasicBlock *SplitBlock(BasicBlock *Old, Instruction *SplitPt, Pass *P);
+ 
+/// SplitBlockPredecessors - This method transforms BB by introducing a new
+/// basic block into the function, and moving some of the predecessors of BB to
+/// be predecessors of the new block.  The new predecessors are indicated by the
+/// Preds array, which has NumPreds elements in it.  The new block is given a
+/// suffix of 'Suffix'.  This function returns the new block.
+///
+/// This currently updates the LLVM IR, AliasAnalysis, DominatorTree and
+/// DominanceFrontier, but no other analyses.
+BasicBlock *SplitBlockPredecessors(BasicBlock *BB, BasicBlock *const *Preds,
+                                   unsigned NumPreds, const char *Suffix,
+                                   Pass *P = 0);
+  
 } // End llvm namespace
 
 #endif