Re: patch to reduce register pressure from strength reduction

[Joern Rennecke <amylaar at cygnus dot co dot uk>]

> >Could you send me your ld-time.i ?
> 
> Attached.  I pruned it as much as I was able, but this is disgusting
> code and I don't want to risk perturbing the bug out of existence.

Thanks.  I've got a patch now:

Sat Jan 30 02:42:41 1999  J"orn Rennecke <amylaar@cygnus.co.uk>

	* loop.c (strength_reduce): Size reg_map according to reg_iv_type.

*** loop.c-1999013001	Sat Jan 30 02:33:08 1999
--- loop.c	Sat Jan 30 02:41:18 1999
*************** strength_reduce (scan_start, end, loop_t
*** 3665,3670 ****
--- 3665,3671 ----
    int threshold = (loop_has_call ? 1 : 2) * (3 + n_non_fixed_regs);
    /* Map of pseudo-register replacements.  */
    rtx *reg_map;
+   int reg_map_size;
    int call_seen;
    rtx test;
    rtx end_insert_before;
*************** strength_reduce (scan_start, end, loop_t
*** 4418,4426 ****
       so that "decrement and branch until zero" insn can be used.  */
    check_dbra_loop (loop_end, insn_count, loop_start, loop_info);
  
!   /* Create reg_map to hold substitutions for replaceable giv regs.  */
!   reg_map = (rtx *) alloca (max_reg_before_loop * sizeof (rtx));
!   bzero ((char *) reg_map, max_reg_before_loop * sizeof (rtx));
  
    /* Examine each iv class for feasibility of strength reduction/induction
       variable elimination.  */
--- 4419,4430 ----
       so that "decrement and branch until zero" insn can be used.  */
    check_dbra_loop (loop_end, insn_count, loop_start, loop_info);
  
!   /* Create reg_map to hold substitutions for replaceable giv regs.
!      Some givs might have been made from biv increments, so look at
!      reg_iv_type for a suitable size.  */
!   reg_map_size = reg_iv_type->num_elements;
!   reg_map = (rtx *) alloca (reg_map_size * sizeof (rtx));
!   bzero ((char *) reg_map, reg_map_size * sizeof (rtx));
  
    /* Examine each iv class for feasibility of strength reduction/induction
       variable elimination.  */
*************** strength_reduce (scan_start, end, loop_t
*** 4961,4968 ****
      if (GET_CODE (p) == INSN || GET_CODE (p) == JUMP_INSN
   	|| GET_CODE (p) == CALL_INSN)
        {
! 	replace_regs (PATTERN (p), reg_map, max_reg_before_loop, 0);
! 	replace_regs (REG_NOTES (p), reg_map, max_reg_before_loop, 0);
  	INSN_CODE (p) = -1;
        }
  
--- 4965,4972 ----
      if (GET_CODE (p) == INSN || GET_CODE (p) == JUMP_INSN
   	|| GET_CODE (p) == CALL_INSN)
        {
! 	replace_regs (PATTERN (p), reg_map, reg_map_size, 0);
! 	replace_regs (REG_NOTES (p), reg_map, reg_map_size, 0);
  	INSN_CODE (p) = -1;
        }