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passes: Enable split4 with selective scheduling 2 [PR98439]

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As mentioned in the PR, we have 5 split passes (+ splitting during final).
split1 is before RA and is unconditional,
split2 is after RA and is gated on optimize > 0,
split3 is before sched2 and is gated on
  defined(INSN_SCHEDULING) && optimize > 0 && flag_schedule_insns_after_reload
split4 is before regstack and is gated on
  HAVE_ATTR_length && defined (STACK_REGS) && !gate (split3)
split5 is before shorten_branches and is gated on
  HAVE_ATTR_length && !defined (STACK_REGS)
and the splitting during final works only when !HAVE_ATTR_length.
STACK_REGS is a macro enabled only on i386/x86_64.

The problem with the following testcase is that split3 before sched2
is the last splitting pass for the target/command line options set,
but selective scheduling unlike normal scheduling can create new
instructions that need to be split, which means we ICE during final as
there are insns that require splitting but nothing split them.

This patch fixes it by doing split4 also when -fselective-scheduling2
is enabled on x86 and split3 has been run.  As that option isn't on
by default, it should slow down compilation only for those that enable
that option.

2021-02-13  Jakub Jelinek  <jakub@redhat.com>

	PR rtl-optimization/98439
	* recog.c (pass_split_before_regstack::gate): Enable even when
	pass_split_before_sched2 is enabled if -fselective-scheduling2 is
	on.

	* gcc.target/i386/pr98439.c: New test.
This commit is contained in:
Jakub Jelinek 2021-02-13 16:08:29 +01:00
parent a3b38b7781
commit 05402ca65a
2 changed files with 18 additions and 1 deletions
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7
gcc/recog.c
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@ -4532,8 +4532,13 @@ pass_split_before_regstack::gate (function *)
/* If flow2 creates new instructions which need splitting
and scheduling after reload is not done, they might not be
split until final which doesn't allow splitting
if HAVE_ATTR_length. */
if HAVE_ATTR_length. Selective scheduling can result in
further instructions that need splitting. */
#ifdef INSN_SCHEDULING
return !enable_split_before_sched2 () || flag_selective_scheduling2;
#else
return !enable_split_before_sched2 ();
#endif
#else
return false;
#endif

12
gcc/testsuite/gcc.target/i386/pr98439.c Normal file
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@ -0,0 +1,12 @@
/* PR rtl-optimization/98439 */
/* { dg-do compile } */
/* { dg-options "-march=nehalem -O2 -fselective-scheduling2 -fno-cprop-registers" } */
int v;
int bar (int, int, int, int, int, int, int);
int
foo (void)
{
return bar (0, 0, 0, 0, 0, 0, v > 0 ? v : 0);
}