On Sun, Nov 25, 2012 at 9:44 PM, Steven Bosscher wrote:
> On Sat, Nov 24, 2012 at 2:09 AM, Steven Bosscher wrote:
>> On Fri, Nov 23, 2012 at 11:45 PM, Steven Bosscher wrote:
>>> Removing the note is easier but it may hurt optimization later on:
>>> CSE2 puts the note back in but this introduces a pass ordering
>>> dependency. Perhaps that's not a big problem, but I'm not sure...
>>
>> Hmm, actually CSE2 fails to put the note back, I guess because it's a
>> local CSE pass only...
>
> Here's another possible fix: Just punt on all REG_EQUAL notes for the
> IV. It's a bit of a big hammer, but there are no code changes in my
> set of cc1-i files (compiled with -funroll-loops) on x86_64 and
> powerpc64 so apparently it's not all that important to keep the notes.
>
> Comments on this one?
Or rather this one. Same hammer, different color. It turns out that
the rtlanal.c change caused problems, so I've got to use a home-brewn
equivalent of remove_reg_equal_equiv_notes_for_regno...
Test case is unchanged so I'm omitting it here.
Ciao!
Steven
gcc/
* loop-unroll.c (struct iv_to_split): Add new 'orig_var' member.
(analyze_iv_to_split_insn): Record it.
(maybe_strip_eq_note_for_split_iv): New function to remove REG_EQUAL
notes that refer to IVs that are being split.
(apply_opt_in_copies): Use maybe_strip_eq_note_for_split_iv. Twice.
Use FOR_BB_INSNS_SAFE.
testsuite/
* gcc.dg/pr55006.c: New test.
Index: loop-unroll.c
===================================================================
--- loop-unroll.c (revision 193394)
+++ loop-unroll.c (working copy)
@@ -74,6 +74,7 @@ along with GCC; see the file COPYING3.
struct iv_to_split
{
rtx insn; /* The insn in that the induction variable occurs. */
+ rtx orig_var; /* The variable (register) for the IV before
split. */
rtx base_var; /* The variable on that the values in the
further
iterations are based. */
rtx step; /* Step of the induction variable. */
@@ -1833,6 +1834,7 @@ analyze_iv_to_split_insn (rtx insn)
/* Record the insn to split. */
ivts = XNEW (struct iv_to_split);
ivts->insn = insn;
+ ivts->orig_var = dest;
ivts->base_var = NULL_RTX;
ivts->step = iv.step;
ivts->next = NULL;
@@ -2253,6 +2255,32 @@ combine_var_copies_in_loop_exit (struct
emit_insn_after (seq, insn);
}
+/* Strip away REG_EQUAL notes for IVs we're splitting.
+
+ Updating REG_EQUAL notes for IVs we split is tricky: We
+ cannot tell until after unrolling, DF-rescanning, and liveness
+ updating, whether an EQ_USE is reached by the split IV while
+ the IV reg is still live. See PR55006.
+
+ ??? We cannot use remove_reg_equal_equiv_notes_for_regno,
+ because RTL loop-iv requires us to defer rescanning insns and
+ any notes attached to them. So resort to old techniques... */
+
+static void
+maybe_strip_eq_note_for_split_iv (struct opt_info *opt_info, rtx insn)
+{
+ struct iv_to_split *ivts;
+ rtx note = find_reg_equal_equiv_note (insn);
+ if (! note)
+ return;
+ for (ivts = opt_info->iv_to_split_head; ivts; ivts = ivts->next)
+ if (reg_mentioned_p (ivts->orig_var, note))
+ {
+ remove_note (insn, note);
+ return;
+ }
+}
+
/* Apply loop optimizations in loop copies using the
data which gathered during the unrolling. Structure
OPT_INFO record that data.
@@ -2293,9 +2321,8 @@ apply_opt_in_copies (struct opt_info *op
unrolling);
bb->aux = 0;
orig_insn = BB_HEAD (orig_bb);
- for (insn = BB_HEAD (bb); insn != NEXT_INSN (BB_END (bb)); insn = next)
+ FOR_BB_INSNS_SAFE (bb, insn, next)
{
- next = NEXT_INSN (insn);
if (!INSN_P (insn)
|| (DEBUG_INSN_P (insn)
&& TREE_CODE (INSN_VAR_LOCATION_DECL (insn)) == LABEL_DECL))
@@ -2313,6 +2340,8 @@ apply_opt_in_copies (struct opt_info *op
/* Apply splitting iv optimization. */
if (opt_info->insns_to_split)
{
+ maybe_strip_eq_note_for_split_iv (opt_info, insn);
+
ivts = (struct iv_to_split *)
htab_find (opt_info->insns_to_split, &ivts_templ);
@@ -2378,6 +2407,8 @@ apply_opt_in_copies (struct opt_info *op
ivts_templ.insn = orig_insn;
if (opt_info->insns_to_split)
{
+ maybe_strip_eq_note_for_split_iv (opt_info, orig_insn);
+
ivts = (struct iv_to_split *)
htab_find (opt_info->insns_to_split, &ivts_templ);
if (ivts)
