Previously, RecursivelyDeleteDeadInstructions provided an option

of returning a list of pointers to Values that are deleted. This was
unsafe, because the pointers in the list are, by nature of what
RecursivelyDeleteDeadInstructions does, always dangling. Replace this
with a simple callback mechanism. This may eventually be removed if
all clients can reasonably be expected to use CallbackVH.

Use this to factor out the dead-phi-cycle-elimination code from LSR
utility function, and generalize it to use the
RecursivelyDeleteTriviallyDeadInstructions utility function.

This makes LSR more aggressive about eliminating dead PHI cycles;
adjust tests to either be less trivial or to simply expect fewer
instructions.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@70636 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 9 insertions, 2 deletions

diff --git a/include/llvm/Transforms/Utils/BasicBlockUtils.h b/include/llvm/Transforms/Utils/BasicBlockUtils.h
index a629b119bc..6105416a40 100644
--- a/include/llvm/Transforms/Utils/BasicBlockUtils.h
+++ b/include/llvm/Transforms/Utils/BasicBlockUtils.h
@@ -25,6 +25,7 @@ namespace llvm {
 class Instruction;
 class Pass;
 class AliasAnalysis;
+class ValueDeletionListener;
 
 /// DeleteDeadBlock - Delete the specified block, which must have no
 /// predecessors.
@@ -36,8 +37,14 @@ void DeleteDeadBlock(BasicBlock *BB);
 /// when all entries to the PHI nodes in a block are guaranteed equal, such as
 /// when the block has exactly one predecessor.
 void FoldSingleEntryPHINodes(BasicBlock *BB);
-  
-  
+
+/// DeleteDeadPHIs - Examine each PHI in the given block and delete it if it
+/// is dead. Also recursively delete any operands that become dead as
+/// a result. This includes tracing the def-use list from the PHI to see if
+/// it is ultimately unused or if it reaches an unused cycle.  If a
+/// ValueDeletionListener is specified, it is notified of the deletions.
+void DeleteDeadPHIs(BasicBlock *BB, ValueDeletionListener *VDL = 0);
+
 /// 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);