Add a target hook to allow changing the tail duplication limit based on the

contents of the block to be duplicated.  Use this for ARM Cortex A8/9 to
be more aggressive tail duplicating indirect branches, since it makes it
much more likely that they will be predicted in the branch target buffer.
Testcase coming soon.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@89187 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 7 insertions, 0 deletions

diff --git a/include/llvm/Target/TargetInstrInfo.h b/include/llvm/Target/TargetInstrInfo.h
index 40b7780..43fd54e 100644
--- a/include/llvm/Target/TargetInstrInfo.h
+++ b/include/llvm/Target/TargetInstrInfo.h
@@ -536,6 +536,13 @@ public:
   /// length.
   virtual unsigned getInlineAsmLength(const char *Str,
                                       const MCAsmInfo &MAI) const;
+
+  /// TailDuplicationLimit - Returns the limit on the number of instructions
+  /// in basic block MBB beyond which it will not be tail-duplicated.
+  virtual unsigned TailDuplicationLimit(const MachineBasicBlock &MBB,
+                                        unsigned DefaultLimit) const {
+    return DefaultLimit;
+  }
 };
 
 /// TargetInstrInfoImpl - This is the default implementation of