On Sat, 2014-04-19 at 15:55 +0200, Steven Bosscher wrote:
> On Sat, Apr 19, 2014 at 3:24 PM, Steven Bosscher wrote:
> > On Tue, Mar 11, 2014 at 8:00 PM, David Malcolm wrote:
> >> Investigation revealed the issue to be a CFG from the previous compile
> >> being kept alive by this GC root in gcse.c:
> >> static GTY(()) rtx test_insn;
> >>
> >> This wouldn't it itself be an issue, but one (or more) of the edges had:
> >
> > But this is an issue! This is not supposed to be possible.
> >
> > test_insn is not in the insns chain and also not in a basic block, so
> > it should never keep a CFG alive.
> >
> > Your patch papers over a bigger issue: How does test_insn end up
> > preventing the CFG from being garbage-collected.
>
>
> The only way this could happen, that I can think of, is a reference
> from SET_SRC into the insn stream (like a label_ref).
>
> Can you please try and see if the patch below fixes your problem?
Thanks; your patch does indeed fix the issue: with it, I no longer need
the band-aid from my patch to be able to run the jit testsuite with full
optimization.
>
> Ciao!
> Steven
>
>
>
> * gcse.c (can_assign_to_reg_without_clobbers_p): Do not let pointers
> from test_insn into GGC space escape via SET_SRC.
>
> Index: gcse.c
> ===================================================================
> --- gcse.c (revision 209530)
> +++ gcse.c (working copy)
> @@ -849,6 +849,7 @@ can_assign_to_reg_without_clobbers_p (rtx x)
> {
> int num_clobbers = 0;
> int icode;
> + bool can_assign = false;
>
> /* If this is a valid operand, we are OK. If it's VOIDmode, we aren't. */
> if (general_operand (x, GET_MODE (x)))
> @@ -866,6 +867,7 @@ can_assign_to_reg_without_clobbers_p (rtx x)
> FIRST_PSEUDO_REGISTER * 2),
> const0_rtx));
> NEXT_INSN (test_insn) = PREV_INSN (test_insn) = 0;
> + INSN_LOCATION (test_insn) = UNKNOWN_LOCATION;
> }
>
> /* Now make an insn like the one we would make when GCSE'ing and see if
> @@ -874,16 +876,19 @@ can_assign_to_reg_without_clobbers_p (rtx x)
> SET_SRC (PATTERN (test_insn)) = x;
>
> icode = recog (PATTERN (test_insn), test_insn, &num_clobbers);
> - if (icode < 0)
> - return false;
> -
> - if (num_clobbers > 0 && added_clobbers_hard_reg_p (icode))
> - return false;
> -
> - if (targetm.cannot_copy_insn_p && targetm.cannot_copy_insn_p (test_insn))
> - return false;
> -
> - return true;
> +
> + /* If the test insn is valid and doesn't need clobbers, and the target also
> + has no objections, we're good. */
> + if (icode != 0
> + && (num_clobbers == 0 || !added_clobbers_hard_reg_p (icode))
> + && ! (targetm.cannot_copy_insn_p
> + && targetm.cannot_copy_insn_p (test_insn)))
> + can_assign = true;
> +
> + /* Make sure test_insn doesn't have any pointers into GC space. */
> + SET_SRC (PATTERN (test_insn)) = NULL_RTX;
> +
> + return can_assign;
> }
>
> /* Return nonzero if the operands of expression X are unchanged from the
