From: Hans-Peter Nilsson <hp@axis.com>
Date: Mon, 10 Feb 2020 03:03:43 +0000 (+0100)
Subject: dbr: Filter-out TARGET_FLAGS_REGNUM from end_of_function_needs.
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=2c2d405829ebb18de5357cc6319614035b420519;p=gcc.git

dbr: Filter-out TARGET_FLAGS_REGNUM from end_of_function_needs.

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.
---

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 75cc642b5a0..39330ba0515 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -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
diff --git a/gcc/resource.c b/gcc/resource.c
index 32faa73fd5f..0a9d5943abc 100644
--- a/gcc/resource.c
+++ b/gcc/resource.c
@@ -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));