patch for ia64 epilogue

[Andrew Macleod <amacleod at cygnus dot com>]

If we have swapped the names of r2 and HARD_FRAME_POINTER_REGNUM in the
prologue code, we don't change it back until ia64_function_epilogue ().
When expand_epilogue is called, and if the sibcall_p flag is set, we
issue an alloc insn. This alloc insn uses GR_REG(2), which
may turn out to be loc79 if the register names have been swapped...

Oh, and we also want to avoid issuing it if its parameters are all 0 too....
The executable chokes on an invalid insn if we do that.

This allows the memcheck* family of testcases in torture to compile
and execute.

Checked into mainline and 3.0 branch.  Verified on ia64 and approved by rth.

Andrew


	* config/ia64/ia64.c (ia64_expand_epilogue): Make sure we are issuing 
	"r2" to the assembly file. Only issue allocs with non-zero parameters.

Index: ia64.c
===================================================================
RCS file: /cvs/cvsfiles/devo/gcc/config/ia64/ia64.c,v
retrieving revision 1.95
diff -c -p -r1.95 ia64.c
*** ia64.c	2001/05/14 17:57:41	1.95
--- ia64.c	2001/05/18 19:14:06
*************** ia64_expand_epilogue (sibcall_p)
*** 2400,2416 ****
    if (! sibcall_p)
      emit_jump_insn (gen_return_internal (gen_rtx_REG (DImode, BR_REG (0))));
    else
!     /* We must emit an alloc to force the input registers to become output
!        registers.  Otherwise, if the callee tries to pass its parameters
!        through to another call without an intervening alloc, then these
!        values get lost.  */
!     /* ??? We don't need to preserve all input registers.  We only need to
!        preserve those input registers used as arguments to the sibling call.
!        It is unclear how to compute that number here.  */
!     emit_insn (gen_alloc (gen_rtx_REG (DImode, GR_REG (2)),
! 			  GEN_INT (0), GEN_INT (0),
! 			  GEN_INT (current_frame_info.n_input_regs),
! 			  GEN_INT (0)));
  }
  
  /* Return 1 if br.ret can do all the work required to return from a
--- 2400,2428 ----
    if (! sibcall_p)
      emit_jump_insn (gen_return_internal (gen_rtx_REG (DImode, BR_REG (0))));
    else
!     {
!       int fp = GR_REG (2);
!       /* We need a throw away register here, r0 and r1 are reserved, so r2 is the
! 	 first available call clobbered register.  If there was a frame_pointer 
! 	 register, we may have swapped the names of r2 and HARD_FRAME_POINTER_REGNUM, 
! 	 so we have to make sure we're using the string "r2" when emitting
! 	 the register name for the assmbler.  */
!       if (current_frame_info.reg_fp && current_frame_info.reg_fp == GR_REG (2))
! 	fp = HARD_FRAME_POINTER_REGNUM;
! 
!       /* We must emit an alloc to force the input registers to become output
! 	 registers.  Otherwise, if the callee tries to pass its parameters
! 	 through to another call without an intervening alloc, then these
! 	 values get lost.  */
!       /* ??? We don't need to preserve all input registers.  We only need to
! 	 preserve those input registers used as arguments to the sibling call.
! 	 It is unclear how to compute that number here.  */
!       if (current_frame_info.n_input_regs != 0)
! 	emit_insn (gen_alloc (gen_rtx_REG (DImode, fp),
! 			      GEN_INT (0), GEN_INT (0),
! 			      GEN_INT (current_frame_info.n_input_regs),
! 			      GEN_INT (0)));
!     }
  }
  
  /* Return 1 if br.ret can do all the work required to return from a