Hi!
On Thu, Jul 23, 2020 at 04:56:14PM +0100, Jozef Lawrynowicz wrote:
> +static int
> +msp430_insn_cost (rtx_insn *insn, bool speed ATTRIBUTE_UNUSED)
> +{
> + int cost;
> +
> + if (recog_memoized (insn) < 0)
> + return 0;
> +
> + cost = get_attr_length (insn);
> + if (TARGET_DEBUG_INSN_COSTS)
> + {
> + fprintf (stderr, "cost %d for insn:\n", cost);
> + debug_rtx (insn);
> + }
> +
> + /* The returned cost must be relative to COSTS_N_INSNS (1). An insn with a
> + length of 2 bytes is the smallest possible size and so must be
> equivalent
> + to COSTS_N_INSNS (1). */
> + return COSTS_N_INSNS (cost) / (2 * COSTS_N_INSNS (1));
This is the same as "cost / 2", so "length / 2" here, which doesn't look
right. The returned value should have the same "unit" as COSTS_N_INSNS
does, so maybe you want COSTS_N_INSNS (length / 2) ?
> + /* FIXME Add more detailed costs when optimizing for speed.
> + For now the length of the instruction is a good approximiation and
> roughly
> + correlates with cycle cost. *
COSTS_N_INSNS (1) is 4, so that you can make things cost 5, 6, 7 to be a
cost intermediate to COSTS_N_INSNS (1) and COSTS_N_INSNS (2). This is
very useful, scaling down the costs destroys that.
> +mdebug-insn-costs
> +Target Report Mask(DEBUG_INSN_COSTS)
> +Print insns and their costs as calculated by TARGET_INSN_COSTS.
It is already printed in the generated asm with -dp? Not sure if you
want more detail than that.
'-dp'
Annotate the assembler output with a comment indicating which
pattern and alternative is used. The length and cost of each
instruction are also printed.
Segher
