[gcc(refs/vendors/ARM/heads/arm-perf-staging)] rs6000: enable -fweb for small loops unrolling

[Tamar Christina]

https://gcc.gnu.org/g:47c39faa67cc7bd567793b62718ab5e4f931e8d0

commit 47c39faa67cc7bd567793b62718ab5e4f931e8d0
Author: guojiufu <guojiufu@linux.ibm.com>
Date:   Mon Apr 27 14:08:20 2020 +0800

    rs6000: enable -fweb for small loops unrolling
    
    Previously -fweb was disabled if only unroll small loops.  After that
    we find there is cases where it could help to rename pseudos and avoid
    some anti-dependence which may occur after unroll.
    
    This patch enables -fweb for small loops unrolling.
    
    2020-04-27  Jiufu Guo   <guojiufu@cn.ibm.com>
    
            * common/config/rs6000/rs6000-common.c
            (rs6000_option_optimization_table) [OPT_LEVELS_ALL]: Remove turn off
            -fweb.
            * config/rs6000/rs6000.c (rs6000_option_override_internal): Avoid to
            set flag_web.

Diff:
---
 gcc/ChangeLog                            | 8 ++++++++
 gcc/common/config/rs6000/rs6000-common.c | 6 +++---
 gcc/config/rs6000/rs6000.c               | 4 +---
 3 files changed, 12 insertions(+), 6 deletions(-)

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 54cc55c5e8d..477d2a7163c 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,11 @@
+2020-04-27  Jiufu Guo   <guojiufu@cn.ibm.com>
+
+	* common/config/rs6000/rs6000-common.c
+	(rs6000_option_optimization_table) [OPT_LEVELS_ALL]: Remove turn off
+	-fweb.
+	* config/rs6000/rs6000.c (rs6000_option_override_internal): Avoid to
+	set flag_web.
+
 2020-04-27  Martin Liska  <mliska@suse.cz>
 
 	PR lto/94659
diff --git a/gcc/common/config/rs6000/rs6000-common.c b/gcc/common/config/rs6000/rs6000-common.c
index 4f38d566844..ee37b9dc90b 100644
--- a/gcc/common/config/rs6000/rs6000-common.c
+++ b/gcc/common/config/rs6000/rs6000-common.c
@@ -38,9 +38,9 @@ static const struct default_options rs6000_option_optimization_table[] =
        loops at -O2 and above by default.  */
     { OPT_LEVELS_2_PLUS_SPEED_ONLY, OPT_funroll_loops, NULL, 1 },
     { OPT_LEVELS_2_PLUS_SPEED_ONLY, OPT_munroll_only_small_loops, NULL, 1 },
-    /* -fweb and -frename-registers are useless in general for rs6000,
-       turn them off.  */
-    { OPT_LEVELS_ALL, OPT_fweb, NULL, 0 },
+
+    /* -frename-registers leads to non-optimal codegen and performance
+       on rs6000, turn it off by default.  */
     { OPT_LEVELS_ALL, OPT_frename_registers, NULL, 0 },
 
     /* Double growth factor to counter reduced min jump length.  */
diff --git a/gcc/config/rs6000/rs6000.c b/gcc/config/rs6000/rs6000.c
index aa632ea8f4a..2007617cdee 100644
--- a/gcc/config/rs6000/rs6000.c
+++ b/gcc/config/rs6000/rs6000.c
@@ -4557,7 +4557,7 @@ rs6000_option_override_internal (bool global_init_p)
 			   SCHED_PRESSURE_MODEL);
 
       /* Explicit -funroll-loops turns -munroll-only-small-loops off, and
-	 turns -fweb and -frename-registers on.  */
+	 turns -frename-registers on.  */
       if ((global_options_set.x_flag_unroll_loops && flag_unroll_loops)
 	   || (global_options_set.x_flag_unroll_all_loops
 	       && flag_unroll_all_loops))
@@ -4566,8 +4566,6 @@ rs6000_option_override_internal (bool global_init_p)
 	    unroll_only_small_loops = 0;
 	  if (!global_options_set.x_flag_rename_registers)
 	    flag_rename_registers = 1;
-	  if (!global_options_set.x_flag_web)
-	    flag_web = 1;
 	}
 
       /* If using typedef char *va_list, signal that