Re-apply r127953 with fixes: eliminate empty return block if it has no predecessors; update dominator tree if cfg is modified.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@127981 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 8 insertions, 0 deletions

diff --git a/include/llvm/Target/TargetLowering.h b/include/llvm/Target/TargetLowering.h
index 5b3f2b35bf..6b3c45adc5 100644
--- a/include/llvm/Target/TargetLowering.h
+++ b/include/llvm/Target/TargetLowering.h
@@ -1287,6 +1287,14 @@ public:
     return false;
   }
 
+  /// mayBeEmittedAsTailCall - Return true if the target may be able emit the
+  /// call instruction as a tail call. This is used by optimization passes to
+  /// determine if it's profitable to duplicate return instructions to enable
+  /// tailcall optimization.
+  virtual bool mayBeEmittedAsTailCall(CallInst *CI) const {
+    return false;
+  }
+
   /// getTypeForExtArgOrReturn - Return the type that should be used to zero or
   /// sign extend a zeroext/signext integer argument or return value.
   /// FIXME: Most C calling convention requires the return type to be promoted,