Change the definition of TargetRegisterInfo::getCrossCopyRegClass to be more

flexible.

If it returns a register class that's different from the input, then that's the
register class used for cross-register class copies.
If it returns a register class that's the same as the input, then no cross-
register class copies are needed (normal copies would do).
If it returns null, then it's not at all possible to copy registers of the
specified register class.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@127368 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 4 insertions, 2 deletions

diff --git a/include/llvm/Target/TargetRegisterInfo.h b/include/llvm/Target/TargetRegisterInfo.h
index 1c5d7c7118..4c63568786 100644
--- a/include/llvm/Target/TargetRegisterInfo.h
+++ b/include/llvm/Target/TargetRegisterInfo.h
@@ -588,8 +588,10 @@ public:
   }
 
   /// getCrossCopyRegClass - Returns a legal register class to copy a register
-  /// in the specified class to or from. Returns NULL if it is possible to copy
-  /// between a two registers of the specified class.
+  /// in the specified class to or from. If it is possible to copy the register
+  /// directly without using a cross register class copy, return the specified
+  /// RC. Returns NULL if it is not possible to copy between a two registers of
+  /// the specified class.
   virtual const TargetRegisterClass *
   getCrossCopyRegClass(const TargetRegisterClass *RC) const {
     return NULL;