Re: Scheduling fix (fixes gcc.c-torture/execute/980506-1.c on ppc)

[Franz Sirl <Franz dot Sirl-kernel at lauterbach dot com>]

At 05:24 25.08.98 , Geoff Keating wrote:
>
>The testcase, under '-O -fsched-verbose-9 -fschedule-insns', generates
>RTL like the following:
>
>;; Function clear_modes
>
>...
>
>;; Start of basic block 2, registers live: 1 [1] 31 [31] 81 84
>(code_label 16 15 18 2 ("blah"))
>
>(note 18 16 19 "" NOTE_INSN_DELETED)
>
>(jump_insn 19 18 0 (set (pc)
>        (if_then_else (ne (reg:CC 84)
>                (const_int 0))
>            (label_ref 11)
>            (pc))) 634 {jump-4} (nil)
>    (nil))
>;; End of basic block 2
>
>
>;; Function main
>
>...
>
>
>Now, basic block 2 has two exits.  One exit goes back to basic block
>1.  The other goes off the edge of the procedure.  Unfortunately,
>haifa only notices the first one, because the second exit doesn't go
>to any basic block, and thinks basic block 2 has only one exit; so the
>branch must be taken with 100% probability:
>
>;;   ------------ REGIONS ----------
>
>;;      rgn 0 nr_blocks 2:
>;;      bb/block:  0/2  1/1 
>
>;;      rgn 1 nr_blocks 1:
>;;      bb/block:  0/0 
>
>;;  bb_prob(1, 1) = 100
>
>For the test case, the branch is actually 0% probability, and haifa
>then mis-schedules the procedure.
>
>If the fix below is not acceptable, then you must go through
>haifa-sched.c and fix every place where it examines the flow graph
>(that is, everywhere in haifa-sched.c) to allow for blocks like block
>2 in the above.  The immediate problem is in compute_dom_prob_ps.

Hi Geoff,

is this patch needed in addition to this one:

Tue Aug 18 10:32:11 1998  Jeffrey A Law  (law@cygnus.com)

        * haifa-sched.c (sched_analyze): Put all JUMP_INSNs on the last
        pending memory flush list.

This patch alone fixed 980506-1.c for me and others. Doesn't it fix all
possible cases?

Franz.