Re-apply r112883:

"For ARM stack frames that utilize variable sized objects and have either
large local stack areas or require dynamic stack realignment, allocate a
base register via which to access the local frame. This allows efficient
access to frame indices not accessible via the FP (either due to being out
of range or due to dynamic realignment) or the SP (due to variable sized
object allocation). In particular, this greatly improves efficiency of access
to spill slots in Thumb functions which contain VLAs."

r112986 fixed a latent bug exposed by the above.

llvm-svn: 112989

1 files changed, 6 insertions, 0 deletions

diff --git a/llvm/lib/Target/ARM/ARMBaseRegisterInfo.h b/llvm/lib/Target/ARM/ARMBaseRegisterInfo.h
index c814f998d5b..fa2eb6c1049 100644
--- a/llvm/lib/Target/ARM/ARMBaseRegisterInfo.h
+++ b/llvm/lib/Target/ARM/ARMBaseRegisterInfo.h
@@ -52,6 +52,11 @@ protected:
   /// FramePtr - ARM physical register used as frame ptr.
   unsigned FramePtr;
 
+  /// BasePtr - ARM physical register used as a base ptr in complex stack
+  /// frames. I.e., when we need a 3rd base, not just SP and FP, due to
+  /// variable size stack objects.
+  unsigned BasePtr;
+
   // Can be only subclassed.
   explicit ARMBaseRegisterInfo(const ARMBaseInstrInfo &tii,
                                const ARMSubtarget &STI);
@@ -102,6 +107,7 @@ public:
                           MachineFunction &MF) const;
 
   bool hasFP(const MachineFunction &MF) const;
+  bool hasBasePointer(const MachineFunction &MF) const;
 
   bool canRealignStack(const MachineFunction &MF) const;
   bool needsStackRealignment(const MachineFunction &MF) const;