move some generally useful functions out of jump threading

into libanalysis and transformutils.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86735 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 24 insertions, 0 deletions

diff --git a/include/llvm/Analysis/InstructionSimplify.h b/include/llvm/Analysis/InstructionSimplify.h
index bb5c811fe2..aa5c0f554b 100644
--- a/include/llvm/Analysis/InstructionSimplify.h
+++ b/include/llvm/Analysis/InstructionSimplify.h
@@ -59,6 +59,15 @@ namespace llvm {
   /// instruction.  If not, this returns null.
   Value *SimplifyInstruction(Instruction *I, const TargetData *TD = 0);
   
+  
+  /// ReplaceAndSimplifyAllUses - Perform From->replaceAllUsesWith(To) and then
+  /// delete the From instruction.  In addition to a basic RAUW, this does a
+  /// recursive simplification of the updated instructions.  This catches
+  /// things where one simplification exposes other opportunities.  This only
+  /// simplifies and deletes scalar operations, it does not change the CFG.
+  ///
+  void ReplaceAndSimplifyAllUses(Instruction *From, Value *To,
+                                 const TargetData *TD = 0);
 } // end namespace llvm
 
 #endif
diff --git a/include/llvm/Transforms/Utils/Local.h b/include/llvm/Transforms/Utils/Local.h
index 24be83cb3d..292af1dbfc 100644
--- a/include/llvm/Transforms/Utils/Local.h
+++ b/include/llvm/Transforms/Utils/Local.h
@@ -78,6 +78,21 @@ void RecursivelyDeleteDeadPHINode(PHINode *PN);
 //  Control Flow Graph Restructuring.
 //
 
+/// RemovePredecessorAndSimplify - Like BasicBlock::removePredecessor, this
+/// method is called when we're about to delete Pred as a predecessor of BB.  If
+/// BB contains any PHI nodes, this drops the entries in the PHI nodes for Pred.
+///
+/// Unlike the removePredecessor method, this attempts to simplify uses of PHI
+/// nodes that collapse into identity values.  For example, if we have:
+///   x = phi(1, 0, 0, 0)
+///   y = and x, z
+///
+/// .. and delete the predecessor corresponding to the '1', this will attempt to
+/// recursively fold the 'and' to 0.
+void RemovePredecessorAndSimplify(BasicBlock *BB, BasicBlock *Pred,
+                                  TargetData *TD = 0);
+    
+  
 /// MergeBasicBlockIntoOnlyPred - BB is a block with one predecessor and its
 /// predecessor is known to have one successor (BB!).  Eliminate the edge
 /// between them, moving the instructions in the predecessor into BB.  This