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Commit 823918ae by Tom de Vries Committed by Tom de Vries
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re PR target/43920 (Choosing conditional execution over conditional branches for… 

re PR target/43920 (Choosing conditional execution over conditional branches for code size in some cases.)

2011-04-07  Tom de Vries  <tom@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.

From-SVN: r172091
parent 472c95f5
Showing with 108 additions and 18 deletions
gcc/ChangeLog
2011-04-07 Tom de Vries <tom@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.
2011-04-07 Tom de Vries <tom@codesourcery.com>
PR target/43920
* cfgcleanup.c (equal_different_set_p, can_replace_by, merge_dir): New
function.
(old_insns_match_p): Change return type. Replace return false/true with
......
gcc/cfgcleanup.c
......@@ -1174,6 +1174,43 @@ merge_notes (rtx i1, rtx i2)
}
}
/* 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 either equivalent, or allow forward or backward
replacement. Store the first insns for that sequence in *F1 and *F2 and
......@@ -1194,6 +1231,7 @@ flow_find_cross_jump (basic_block bb1, basic_block bb2, rtx *f1, rtx *f2,
int ninsns = 0;
rtx p1;
enum replace_direction dir, last_dir, afterlast_dir;
bool follow_fallthru, did_fallthru;
if (dir_p)
dir = *dir_p;
......@@ -1227,12 +1265,31 @@ flow_find_cross_jump (basic_block bb1, basic_block bb2, rtx *f1, rtx *f2,
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;
......@@ -1273,12 +1330,14 @@ flow_find_cross_jump (basic_block bb1, basic_block bb2, rtx *f1, rtx *f2,
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);
......@@ -1710,6 +1769,7 @@ try_crossjump_to_edge (int mode, edge e1, edge e2)
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;
......@@ -1769,6 +1829,13 @@ try_crossjump_to_edge (int mode, edge e1, edge e2)
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
(such that its predecessors will hopefully be redirected and the
......@@ -1791,8 +1858,8 @@ try_crossjump_to_edge (int mode, edge e1, edge e2)
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;
......@@ -1807,7 +1874,7 @@ try_crossjump_to_edge (int mode, edge e1, edge e2)
/* 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);
}
}
......@@ -1848,8 +1915,13 @@ try_crossjump_to_edge (int mode, edge e1, edge e2)
/* 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;
......@@ -1892,24 +1964,32 @@ try_crossjump_to_edge (int mode, edge e1, edge e2)
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. */
......
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