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dbr: Filter-out TARGET_FLAGS_REGNUM from end_of_function_needs.

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Compared to the cc0 version, I noticed a regression in
delay-slot-filling for CRIS for several functions in libgcc with
a similar layout, one being lshrdi3, where with cc0 all
delay-slots were filled, as exposed by the test-case in
gcc.target/cris/pr93372-1.c.

There's one slot that fails to be filled for the decc0rated CRIS
port.  A gdb session shows it is because of the automatic
inclusion of TARGET_FLAGS_REGNUM in "registers needed at the end
of the function" because there are insns in the epilogue that
clobber the condition-code register.  I'm not trying to tell a
clobber from a set, as parallels with set instead of clobber
seems likely to happen too, for targets with TARGET_FLAGS_REGNUM
set.

Other targets with delay-slots and one dedicated often-clobbered
condition-code-register should consider defining
TARGET_FLAGS_REGNUM.  I noticed it improved delay-slot-filling
also in other situations than this.

(Previously approved by Jeff Law.)

gcc:
	* resource.c (init_resource_info): Filter-out TARGET_FLAGS_REGNUM
	from end_of_function_needs.
This commit is contained in:
Hans-Peter Nilsson 2020-02-10 04:03:43 +01:00
parent ce08aac182
commit 2c2d405829
2 changed files with 11 additions and 0 deletions
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5
gcc/ChangeLog
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@ -1,3 +1,8 @@
2020-05-09 Hans-Peter Nilsson <hp@axis.com>
* resource.c (init_resource_info): Filter-out TARGET_FLAGS_REGNUM
from end_of_function_needs.
2020-05-08 Vladimir Makarov <vmakarov@redhat.com>
* ira-color.c (update_costs_from_allocno): Remove

6
gcc/resource.c
View file

@ -21,6 +21,7 @@ along with GCC; see the file COPYING3. If not see
#include "system.h"
#include "coretypes.h"
#include "backend.h"
#include "target.h"
#include "rtl.h"
#include "df.h"
#include "memmodel.h"
@ -1215,6 +1216,11 @@ init_resource_info (rtx_insn *epilogue_insn)
break;
}
/* Filter-out the flags register from those additionally required
registers. */
if (targetm.flags_regnum != INVALID_REGNUM)
CLEAR_HARD_REG_BIT (end_of_function_needs.regs, targetm.flags_regnum);
/* Allocate and initialize the tables used by mark_target_live_regs. */
target_hash_table = XCNEWVEC (struct target_info *, TARGET_HASH_PRIME);
bb_ticks = XCNEWVEC (int, last_basic_block_for_fn (cfun));