[gcc r12-2346] Disable --param vect-partial-vector-usage by default on x86

[gcc r12-2346] Disable --param vect-partial-vector-usage by default on x86

[Richard Biener]

https://gcc.gnu.org/g:a314d50336db752f2ae2c50262956ce4490567ac

commit r12-2346-ga314d50336db752f2ae2c50262956ce4490567ac
Author: Richard Biener <rguenther@suse.de>
Date:   Thu Jul 15 14:30:48 2021 +0200

    Disable --param vect-partial-vector-usage by default on x86
    
    The following defaults --param vect-partial-vector-usage to zero
    for x86_64 matching existing behavior where support for this
    is not present.
    
    2021-07-15  Richard Biener  <rguenther@suse.de>
    
            * config/i386/i386-options.c (ix86_option_override_internal): Set
            param_vect_partial_vector_usage to zero if not set.

Diff:
---
 gcc/config/i386/i386-options.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/gcc/config/i386/i386-options.c b/gcc/config/i386/i386-options.c
index 7cba655595e..3416a4f1752 100644
--- a/gcc/config/i386/i386-options.c
+++ b/gcc/config/i386/i386-options.c
@@ -2834,6 +2834,11 @@ ix86_option_override_internal (bool main_args_p,
 
   SET_OPTION_IF_UNSET (opts, opts_set, param_ira_consider_dup_in_all_alts, 0);
 
+  /* Fully masking the main or the epilogue vectorized loop is not
+     profitable generally so leave it disabled until we get more
+     fine grained control & costing.  */
+  SET_OPTION_IF_UNSET (opts, opts_set, param_vect_partial_vector_usage, 0);
+
   return true;
 }