Reposting, with ChangeLog.
2011-04-01 Tom de Vries <t...@codesourcery.com>
PR target/43920
* cfgcleanup.c (walk_to_nondebug_insn): New function.
(flow_find_cross_jump): Use walk_to_nondebug_insn. Recalculate bb1 and
bb2.
(try_crossjump_to_edge): Handle case that newpos1 or newpos2 is not src1
or src2. Redirect edges to the last basic block. Update frequency and
count on multiple basic blocks in case of fallthru.
diff -u gcc/cfgcleanup.c gcc/cfgcleanup.c
--- gcc/cfgcleanup.c (working copy)
+++ gcc/cfgcleanup.c (working copy)
@@ -1139,6 +1139,43 @@
}
}
+ /* Walks from I1 in BB1 backward till the next non-debug insn, and returns the
+ resulting insn in I1, and the corresponding bb in BB1. At the head of a
+ bb, if there is a predecessor bb that reaches this bb via fallthru, and
+ FOLLOW_FALLTHRU, walks further in the predecessor bb and registers this in
+ DID_FALLTHRU. Otherwise, stops at the head of the bb. */
+
+static void
+walk_to_nondebug_insn (rtx *i1, basic_block *bb1, bool follow_fallthru,
+ bool *did_fallthru)
+{
+ edge fallthru;
+
+ *did_fallthru = false;
+
+ /* Ignore notes. */
+ while (!NONDEBUG_INSN_P (*i1))
+ {
+ if (*i1 != BB_HEAD (*bb1))
+ {
+ *i1 = PREV_INSN (*i1);
+ continue;
+ }
+
+ if (!follow_fallthru)
+ return;
+
+ fallthru = find_fallthru_edge ((*bb1)->preds);
+ if (!fallthru || fallthru->src == ENTRY_BLOCK_PTR_FOR_FUNCTION (cfun)
+ || !single_succ_p (fallthru->src))
+ return;
+
+ *bb1 = fallthru->src;
+ *i1 = BB_END (*bb1);
+ *did_fallthru = true;
+ }
+}
+
/* Look through the insns at the end of BB1 and BB2 and find the longest
sequence that are equivalent. Store the first insns for that sequence
in *F1 and *F2 and return the sequence length.
@@ -1153,6 +1190,7 @@
rtx i1, i2, last1, last2, afterlast1, afterlast2;
int ninsns = 0;
enum replace_direction dir, last_dir, afterlast_dir;
+ bool follow_fallthru, did_fallthru;
if (dir_p)
dir = *dir_p;
@@ -1187,11 +1225,30 @@
while (true)
{
- /* Ignore notes. */
- while (!NONDEBUG_INSN_P (i1) && i1 != BB_HEAD (bb1))
- i1 = PREV_INSN (i1);
-
- while (!NONDEBUG_INSN_P (i2) && i2 != BB_HEAD (bb2))
- i2 = PREV_INSN (i2);
+ /* In the following example, we can replace all jumps to C by jumps to A.
+
+ This removes 4 duplicate insns.
+ [bb A] insn1 [bb C] insn1
+ insn2 insn2
+ [bb B] insn3 insn3
+ insn4 insn4
+ jump_insn jump_insn
+
+ We could also replace all jumps to A by jumps to C, but that leaves B
+ alive, and removes only 2 duplicate insns. In a subsequent crossjump
+ step, all jumps to B would be replaced with jumps to the middle of C,
+ achieving the same result with more effort.
+ So we allow only the first possibility, which means that we don't allow
+ fallthru in the block that's being replaced. */
+
+ follow_fallthru = dir_p && dir != dir_forward;
+ walk_to_nondebug_insn (&i1, &bb1, follow_fallthru, &did_fallthru);
+ if (did_fallthru)
+ dir = dir_backward;
+
+ follow_fallthru = dir_p && dir != dir_backward;
+ walk_to_nondebug_insn (&i2, &bb2, follow_fallthru, &did_fallthru);
+ if (did_fallthru)
+ dir = dir_forward;
if (i1 == BB_HEAD (bb1) || i2 == BB_HEAD (bb2))
break;
@@ -1230,12 +1287,14 @@
Two, it keeps line number notes as matched as may be. */
if (ninsns)
{
+ bb1 = BLOCK_FOR_INSN (last1);
while (last1 != BB_HEAD (bb1) && !NONDEBUG_INSN_P (PREV_INSN (last1)))
last1 = PREV_INSN (last1);
if (last1 != BB_HEAD (bb1) && LABEL_P (PREV_INSN (last1)))
last1 = PREV_INSN (last1);
+ bb2 = BLOCK_FOR_INSN (last2);
while (last2 != BB_HEAD (bb2) && !NONDEBUG_INSN_P (PREV_INSN (last2)))
last2 = PREV_INSN (last2);
@@ -1659,6 +1718,7 @@
int nmatch;
basic_block src1 = e1->src, src2 = e2->src;
basic_block redirect_to, redirect_from, to_remove;
+ basic_block osrc1, osrc2, redirect_edges_to, tmp;
enum replace_direction dir;
rtx newpos1, newpos2;
edge s;
@@ -1720,8 +1780,15 @@
return false;
/* ... and part the second. */
dir = dir_forward;
nmatch = flow_find_cross_jump (src1, src2, &newpos1, &newpos2, &dir);
+
+ osrc1 = src1;
+ osrc2 = src2;
+ if (newpos1 != NULL_RTX)
+ src1 = BLOCK_FOR_INSN (newpos1);
+ if (newpos2 != NULL_RTX)
+ src2 = BLOCK_FOR_INSN (newpos2);
/* Don't proceed with the crossjump unless we found a sufficient number
of matching instructions or the 'from' block was totally matched
@@ -1745,8 +1812,8 @@
rtx label1, label2;
rtx table1, table2;
- if (tablejump_p (BB_END (src1), &label1, &table1)
- && tablejump_p (BB_END (src2), &label2, &table2)
+ if (tablejump_p (BB_END (osrc1), &label1, &table1)
+ && tablejump_p (BB_END (osrc2), &label2, &table2)
&& label1 != label2)
{
replace_label_data rr;
@@ -1761,7 +1828,7 @@
/* Do not replace the label in SRC1->END because when deleting
a block whose end is a tablejump, the tablejump referenced
from the instruction is deleted too. */
- if (insn != BB_END (src1))
+ if (insn != BB_END (osrc1))
for_each_rtx (&insn, replace_label, &rr);
}
}
@@ -1802,8 +1869,13 @@
/* We may have some registers visible through the block. */
df_set_bb_dirty (redirect_to);
+ if (osrc2 == src2)
+ redirect_edges_to = redirect_to;
+ else
+ redirect_edges_to = osrc2;
+
/* Recompute the frequencies and counts of outgoing edges. */
- FOR_EACH_EDGE (s, ei, redirect_to->succs)
+ FOR_EACH_EDGE (s, ei, redirect_edges_to->succs)
{
edge s2;
edge_iterator ei;
@@ -1846,24 +1918,32 @@
s2->dest->count = 0;
}
- if (!redirect_to->frequency && !src1->frequency)
+ if (!redirect_edges_to->frequency && !src1->frequency)
s->probability = (s->probability + s2->probability) / 2;
else
s->probability
- = ((s->probability * redirect_to->frequency +
+ = ((s->probability * redirect_edges_to->frequency +
s2->probability * src1->frequency)
- / (redirect_to->frequency + src1->frequency));
+ / (redirect_edges_to->frequency + src1->frequency));
}
/* Adjust count and frequency for the block. An earlier jump
threading pass may have left the profile in an inconsistent
state (see update_bb_profile_for_threading) so we must be
prepared for overflows. */
- redirect_to->count += src1->count;
- redirect_to->frequency += src1->frequency;
- if (redirect_to->frequency > BB_FREQ_MAX)
- redirect_to->frequency = BB_FREQ_MAX;
- update_br_prob_note (redirect_to);
+ tmp = redirect_to;
+ do
+ {
+ tmp->count += src1->count;
+ tmp->frequency += src1->frequency;
+ if (tmp->frequency > BB_FREQ_MAX)
+ tmp->frequency = BB_FREQ_MAX;
+ if (tmp == redirect_edges_to)
+ break;
+ tmp = find_fallthru_edge (tmp->succs)->dest;
+ }
+ while (true);
+ update_br_prob_note (redirect_edges_to);
/* Edit SRC1 to go to REDIRECT_TO at NEWPOS1. */
