Fix frame index elimination to correctly handle thumb-2 addressing modes that don't allow negative offsets. During frame elimination convert *i12 opcode to a *i8 when necessary due to a negative offset.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@76883 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Target/ARM/Thumb1InstrInfo.h

@@ -34,6 +34,13 @@ public:
   // Return the opcode that implements 'Op', or 0 if no opcode
   unsigned getOpcode(ARMII::Op Op) const;
 
+  // If 'opcode' is an instruction with an unsigned offset that also
+  // has a version with a signed offset, return the opcode for the
+  // version with the signed offset. In 'NumBits' return the number of
+  // bits for the signed offset.
+  unsigned unsignedOffsetOpcodeToSigned(unsigned opcode,
+                                        unsigned *NumBits) const;
+
   // Return true if the block does not fall through.
   bool BlockHasNoFallThrough(const MachineBasicBlock &MBB) const;