The problem is that the new call to cleanup_cfg in gimple_expand_cfg has
short-circuited the machinery that emits nops to carry goto locus at -O0.
The machinery works in CFGLAYOUT mode, but here we're still in CFGRTL.
The attached patch makes it so that forwarder blocks are not deleted by
try_optimize_cfg if CLEANUP_NO_INSN_DEL and partially extends the above
machinery to the CFGRTL mode.
Bootstrapped/regtested on x86_64-suse-linux, applied on the mainline.
2012-05-26 Eric Botcazou <ebotca...@adacore.com>
* cfgcleanup.c (try_optimize_cfg): Do not delete forwarder blocks
if CLEANUP_NO_INSN_DEL.
* cfgrtl.c (unique_locus_on_edge_between_p): New function extracted
from cfg_layout_merge_blocks.
(emit_nop_for_unique_locus_between): New function.
(rtl_merge_blocks): Invoke emit_nop_for_unique_locus_between.
(cfg_layout_merge_blocks): Likewise.
--
Eric Botcazou
Index: cfgcleanup.c
===================================================================
--- cfgcleanup.c (revision 187833)
+++ cfgcleanup.c (working copy)
@@ -2644,7 +2644,7 @@ try_optimize_cfg (int mode)
}
/* If we fall through an empty block, we can remove it. */
- if (!(mode & CLEANUP_CFGLAYOUT)
+ if (!(mode & (CLEANUP_CFGLAYOUT | CLEANUP_NO_INSN_DEL))
&& single_pred_p (b)
&& (single_pred_edge (b)->flags & EDGE_FALLTHRU)
&& !LABEL_P (BB_HEAD (b))
Index: cfgrtl.c
===================================================================
--- cfgrtl.c (revision 187833)
+++ cfgrtl.c (working copy)
@@ -603,6 +603,56 @@ rtl_split_block (basic_block bb, void *i
return new_bb;
}
+/* Return true if the single edge between blocks A and B is the only place
+ in RTL which holds some unique locus. */
+
+static bool
+unique_locus_on_edge_between_p (basic_block a, basic_block b)
+{
+ const int goto_locus = EDGE_SUCC (a, 0)->goto_locus;
+ rtx insn, end;
+
+ if (!goto_locus)
+ return false;
+
+ /* First scan block A backward. */
+ insn = BB_END (a);
+ end = PREV_INSN (BB_HEAD (a));
+ while (insn != end && (!NONDEBUG_INSN_P (insn) || INSN_LOCATOR (insn) == 0))
+ insn = PREV_INSN (insn);
+
+ if (insn != end && locator_eq (INSN_LOCATOR (insn), goto_locus))
+ return false;
+
+ /* Then scan block B forward. */
+ insn = BB_HEAD (b);
+ if (insn)
+ {
+ end = NEXT_INSN (BB_END (b));
+ while (insn != end && !NONDEBUG_INSN_P (insn))
+ insn = NEXT_INSN (insn);
+
+ if (insn != end && INSN_LOCATOR (insn) != 0
+ && locator_eq (INSN_LOCATOR (insn), goto_locus))
+ return false;
+ }
+
+ return true;
+}
+
+/* If the single edge between blocks A and B is the only place in RTL which
+ holds some unique locus, emit a nop with that locus between the blocks. */
+
+static void
+emit_nop_for_unique_locus_between (basic_block a, basic_block b)
+{
+ if (!unique_locus_on_edge_between_p (a, b))
+ return;
+
+ BB_END (a) = emit_insn_after_noloc (gen_nop (), BB_END (a), a);
+ INSN_LOCATOR (BB_END (a)) = EDGE_SUCC (a, 0)->goto_locus;
+}
+
/* Blocks A and B are to be merged into a single block A. The insns
are already contiguous. */
@@ -681,15 +731,25 @@ rtl_merge_blocks (basic_block a, basic_b
/* Delete everything marked above as well as crap that might be
hanging out between the two blocks. */
- BB_HEAD (b) = NULL;
+ BB_END (a) = a_end;
+ BB_HEAD (b) = b_empty ? NULL_RTX : b_head;
delete_insn_chain (del_first, del_last, true);
+ /* When not optimizing CFG and the edge is the only place in RTL which holds
+ some unique locus, emit a nop with that locus in between. */
+ if (!optimize)
+ {
+ emit_nop_for_unique_locus_between (a, b);
+ a_end = BB_END (a);
+ }
+
/* Reassociate the insns of B with A. */
if (!b_empty)
{
update_bb_for_insn_chain (a_end, b_debug_end, a);
- a_end = b_debug_end;
+ BB_END (a) = b_debug_end;
+ BB_HEAD (b) = NULL_RTX;
}
else if (b_end != b_debug_end)
{
@@ -701,11 +761,10 @@ rtl_merge_blocks (basic_block a, basic_b
reorder_insns_nobb (NEXT_INSN (a_end), PREV_INSN (b_debug_start),
b_debug_end);
update_bb_for_insn_chain (b_debug_start, b_debug_end, a);
- a_end = b_debug_end;
+ BB_END (a) = b_debug_end;
}
df_bb_delete (b->index);
- BB_END (a) = a_end;
/* If B was a forwarder block, propagate the locus on the edge. */
if (forwarder_p && !EDGE_SUCC (b, 0)->goto_locus)
@@ -2853,33 +2912,10 @@ cfg_layout_merge_blocks (basic_block a,
try_redirect_by_replacing_jump (EDGE_SUCC (a, 0), b, true);
gcc_assert (!JUMP_P (BB_END (a)));
- /* When not optimizing and the edge is the only place in RTL which holds
+ /* When not optimizing CFG and the edge is the only place in RTL which holds
some unique locus, emit a nop with that locus in between. */
- if (!optimize && EDGE_SUCC (a, 0)->goto_locus)
- {
- rtx insn = BB_END (a), end = PREV_INSN (BB_HEAD (a));
- int goto_locus = EDGE_SUCC (a, 0)->goto_locus;
-
- while (insn != end && (!INSN_P (insn) || INSN_LOCATOR (insn) == 0))
- insn = PREV_INSN (insn);
- if (insn != end && locator_eq (INSN_LOCATOR (insn), goto_locus))
- goto_locus = 0;
- else
- {
- insn = BB_HEAD (b);
- end = NEXT_INSN (BB_END (b));
- while (insn != end && !INSN_P (insn))
- insn = NEXT_INSN (insn);
- if (insn != end && INSN_LOCATOR (insn) != 0
- && locator_eq (INSN_LOCATOR (insn), goto_locus))
- goto_locus = 0;
- }
- if (goto_locus)
- {
- BB_END (a) = emit_insn_after_noloc (gen_nop (), BB_END (a), a);
- INSN_LOCATOR (BB_END (a)) = goto_locus;
- }
- }
+ if (!optimize)
+ emit_nop_for_unique_locus_between (a, b);
/* Possible line number notes should appear in between. */
if (BB_HEADER (b))
