Problems with the way we calculate costs

[Bernd Schmidt]

Jeff Law has reviewed and approved this patch.  I'll check it in after another
bootstrap on ix86.

Bernd

On Wed, 23 Aug 2000, Bernd Schmidt wrote:
> 	* Makefile.in (cse.o): Depend on $(BASIC_BLOCK_H).
> 	* cse.c: Include "basic-block.h".
> 	(struct table_elt): New field REGCOST.
> 	(CHEAP_REG): Delete macro.
> 	(COST): Return 0 for REGs.
> 	(approx_reg_cost_1, approx_reg_cost, preferrable): New functions.
> 	(notreg_cost): Return 0 for appropriate SUBREGs.
> 	(COSTS_N_INSNS): Return N * 2.
> 	(rtx_cost): Return 0 for REGs, and use cost of nested rtx for cheap
> 	SUBREGs.
> 	(CHEAPER): Use new function preferrable.
> 	(insert): Initialize REGCOST member.
> 	(find_best_addr): Use approx_reg_cost for estimation of register
> 	usage.
> 	(cse_insn): Likewise.
> 	* loop.c (iv_add_mult_cost): New function.
> 	(add_cost, shift_cost, mult_cost): Delete variables.
> 	(init_loop): Don't initialize add_cost; reduce copy_cost by half.
> 	(strength_reduce): Use iv_add_mult_cost instead of fixed add_cost.
> 	Make code that detects autoinc opportunities slightly less optimistic.
> 	(simplify_giv_expr): If expression contains other reg that is also a
> 	giv, only increment benefit if this is the only use of that reg.
> 	(consec_sets_giv): Take that change into account.
> 	(combine_givs): Slightly more verbose output.
> 
> 	* i386.h (RTX_COSTS): For MULT, return true cost of multiplication,
> 	not the cost of an equivalent shift.
> 	* sh-protos.h (addsubcosts): Declare.
> 	* sh.c (addsubcosts): New function.
> 	* sh.h (CONST_COSTS): If CONST_OK_FOR_I, then return 0.
> 	(RTX_COSTS): Tweak.  Use addsubcosts.
> 	(ADDRESS_COST): Return higher cost for reg+reg addressing.