On Tue, Apr 12, 2011 at 09:18:01AM +0200, Eric Botcazou wrote:
> > With the second patch, bootstrap succeeded even with gcc_assert (at_end);
> > in update_cfg_for_uncondjump, so either it is always at the end, or at
> > least very often, thus perhaps with the second patch being applied
> > in combine_instructions we could just for INSN_DELETED_P clear
> > last_combined_insn right away, meaning we want to propagate till end of
> > current bb.
>
> Something I don't understand at the moment: why moving last_combined_insn
> down
> to the next insn instead of up to the previous one when it has been deleted?
That is because propagate_for_debug stops at the insn before last, doesn't
process last any longer. So, if there is a DEBUG_INSN right before the jump
being deleted, and it has been propagated into, after the jump is deleted
and retry is done at i2 earlier, following propagate_for_debug won't see
that DEBUG_INSN any longer.
We could certainly change propagate_for_debug, so that it would stop either
before end (NEXT_INSN (BB_END (this_basic_block)) added in this patch), or
after processing last (which doesn't change anything in the non-deleted insn
case, because i3 from any try_combine surely isn't a DEBUG_INSN and
propagate_for_debug only propagates into those), then on deletion set it to
PREV_INSN instead of NEXT_INSN. I wonder whether we couldn't be deleting
the first insn in a basic block, but probably there should be at least a
note before it.
> Wouldn't the latter simplify things, in particular avoid setting it to
> NULL_RTX
> which looks rather awkward to me?
Below is an untested patch (well, just tested on the testcase in question).
If that's what you prefer, I'll bootstrap/regtest it.
Perhaps instead of the assert we could in that case just set
last_combined_insn to insn.
2011-04-12 Jakub Jelinek <ja...@redhat.com>
PR rtl-optimization/48549
* combine.c (propagate_for_debug): Also stop after BB_END of
this_basic_block. Process LAST and just stop processing after it.
(combine_instructions): If last_combined_insn has been deleted,
set last_combined_insn to its PREV_INSN.
* g++.dg/opt/pr48549.C: New test.
--- gcc/combine.c.jj 2011-04-12 09:37:36.000000000 +0200
+++ gcc/combine.c 2011-04-12 09:50:44.000000000 +0200
@@ -1198,8 +1198,18 @@ combine_instructions (rtx f, unsigned in
next = 0;
if (NONDEBUG_INSN_P (insn))
{
- if (last_combined_insn == NULL_RTX
- || DF_INSN_LUID (last_combined_insn) < DF_INSN_LUID (insn))
+ if (last_combined_insn)
+ {
+ while (INSN_DELETED_P (last_combined_insn))
+ last_combined_insn = PREV_INSN (last_combined_insn);
+ gcc_assert (!BARRIER_P (last_combined_insn)
+ && BLOCK_FOR_INSN (last_combined_insn)
+ == this_basic_block);
+ if (DF_INSN_LUID (last_combined_insn)
+ <= DF_INSN_LUID (insn))
+ last_combined_insn = insn;
+ }
+ else
last_combined_insn = insn;
/* See if we know about function return values before this
@@ -2446,19 +2456,21 @@ propagate_for_debug_subst (rtx from, con
}
/* Replace all the occurrences of DEST with SRC in DEBUG_INSNs between INSN
- and LAST. */
+ and LAST, not including INSN, but including LAST. Also stop at the end
+ of THIS_BASIC_BLOCK. */
static void
propagate_for_debug (rtx insn, rtx last, rtx dest, rtx src)
{
- rtx next, loc;
+ rtx next, loc, end = NEXT_INSN (BB_END (this_basic_block));
struct rtx_subst_pair p;
p.to = src;
p.adjusted = false;
next = NEXT_INSN (insn);
- while (next != last)
+ last = NEXT_INSN (last);
+ while (next != last && next != end)
{
insn = next;
next = NEXT_INSN (insn);
--- gcc/testsuite/g++.dg/opt/pr48549.C.jj 2011-04-12 09:41:52.000000000
+0200
+++ gcc/testsuite/g++.dg/opt/pr48549.C 2011-04-12 09:41:52.000000000 +0200
@@ -0,0 +1,63 @@
+// PR rtl-optimization/48549
+// { dg-do compile }
+// { dg-options "-fcompare-debug -O2" }
+
+void
+foo (void *from, void *to)
+{
+ long offset = reinterpret_cast <long>(to) - reinterpret_cast <long>(from);
+ if (offset != static_cast <int>(offset))
+ *(int *) 0xC0DE = 0;
+ reinterpret_cast <int *>(from)[1] = offset;
+}
+struct A
+{
+ A () : a () {}
+ A (void *x) : a (x) {}
+ void *bar () { return a; }
+ void *a;
+};
+struct C;
+struct D;
+struct E : public A
+{
+ C m1 (int);
+ D m2 ();
+ E () {}
+ E (A x) : A (x) {}
+};
+struct C : public E
+{
+ C () {}
+ C (void *x) : E (x) {}
+};
+struct D : public E
+{
+ D (void *x) : E (x) {}
+};
+C
+E::m1 (int x)
+{
+ return (reinterpret_cast <char *>(bar ()) + x);
+}
+D
+E::m2 ()
+{
+ return reinterpret_cast <char *>(bar ());
+}
+struct B
+{
+ E a;
+ unsigned b : 16;
+ unsigned c : 1;
+};
+void
+baz (B *x)
+{
+ for (unsigned i = 0; i < 64; i++)
+ {
+ D d = x[i].a.m2 ();
+ C c = x[i].a.m1 (x[i].c);
+ foo (d.bar (), c.bar ());
+ }
+}
Jakub
