i386: Schedule the only -O0 split pass on x86 after pro_and_epilogue/jump2 [PR92190]

The problem is that x86 is the only target that defines HAVE_ATTR_length and
doesn't schedule any splitting pass at -O0 after pro_and_epilogue.

So, either we go back to handling this during vzeroupper output
(unconditionally, rather than flag_ipa_ra guarded), or we need to tweak the
split* passes for x86.

Seems there are 5 split passes, split1 is run unconditionally before reload,
split2 is run for optimize > 0 or STACK_REGS (x86) after ra but before
epilogue_completed, split3 is run before regstack for STACK_REGS and
optimize and -fno-schedule-insns2, split4 is run before sched2 if sched2 is
run and split5 is run before shorten_branches if HAVE_ATTR_length and not
STACK_REGS.

2020-02-05  Jakub Jelinek  <jakub@redhat.com>

	PR target/92190
	* recog.c (pass_split_after_reload::gate): For STACK_REGS targets,
	don't run when !optimize.
	(pass_split_before_regstack::gate): For STACK_REGS targets, run even
	when !optimize.

1 files changed, 4 insertions, 11 deletions

diff --git a/gcc/recog.c b/gcc/recog.c
index 5dd1a92..5790a58 100644
--- a/gcc/recog.c
+++ b/gcc/recog.c
@@ -3924,14 +3924,7 @@ public:
   virtual bool gate (function *)
     {
       /* If optimizing, then go ahead and split insns now.  */
-      if (optimize > 0)
-	return true;
-
-#ifdef STACK_REGS
-      return true;
-#else
-      return false;
-#endif
+      return optimize > 0;
     }
 
   virtual unsigned int execute (function *)
@@ -3991,12 +3984,12 @@ pass_split_before_regstack::gate (function *)
      split until final which doesn't allow splitting
      if HAVE_ATTR_length.  */
 # ifdef INSN_SCHEDULING
-  return (optimize && !flag_schedule_insns_after_reload);
+  return !optimize || !flag_schedule_insns_after_reload;
 # else
-  return (optimize);
+  return true;
 # endif
 #else
-  return 0;
+  return false;
 #endif
 }