Uses regnotes to analyze whether we can replace insn a by insn b, even
if we cannot replace insn b by insn a. Uses this info in crossjumping.
Thanks,
- Tom
diff -u gcc/cfgcleanup.c gcc/cfgcleanup.c
--- gcc/cfgcleanup.c (working copy)
+++ gcc/cfgcleanup.c (working copy)
@@ -72,7 +72,7 @@
static bool try_crossjump_to_edge (int, edge, edge);
static bool try_crossjump_bb (int, basic_block);
static bool outgoing_edges_match (int, basic_block, basic_block);
-static bool old_insns_match_p (int, rtx, rtx);
+static enum replace_direction old_insns_match_p (int, rtx, rtx);
static void merge_blocks_move_predecessor_nojumps (basic_block, basic_block);
static void merge_blocks_move_successor_nojumps (basic_block, basic_block);
@@ -950,27 +950,108 @@
}
+/* Examine register notes on I1 and I2 and return:
+ - dir_forward if I1 can be replaced by I2, or
+ - dir_backward if I2 can be replaced by I1, or
+ - dir_both if both are the case. */
+
+static enum replace_direction
+can_replace_by (rtx i1, rtx i2)
+{
+ rtx p1, p2, d1, d2, src1, src2, note1, note2;
+ bool c1, c2;
+
+ /* Check for 2 sets. */
+ if (!INSN_P (i1) || !INSN_P (i2))
+ return dir_none;
+ p1 = PATTERN (i1);
+ p2 = PATTERN (i2);
+ if (GET_CODE (p1) != SET || GET_CODE (p2) != SET)
+ return dir_none;
+
+ /* Check that the 2 sets set the same dest. */
+ d1 = SET_DEST (p1);
+ d2 = SET_DEST (p2);
+ if (!(reload_completed
+ ? rtx_renumbered_equal_p (d1, d2) : rtx_equal_p (d1, d2)))
+ return dir_none;
+
+ /* Find identical req_equiv or reg_equal note, which implies that the 2 sets
+ set dest to the same value. */
+ note1 = find_reg_equal_equiv_note (i1);
+ note2 = find_reg_equal_equiv_note (i2);
+ if (!note1 || !note2 || !rtx_equal_p (XEXP (note1, 0), XEXP (note2, 0))
+ || !CONST_INT_P (XEXP (note1, 0)))
+ return dir_none;
+
+ /* Although the 2 sets set dest to the same value, we cannot replace
+ (set (dest) (const_int))
+ by
+ (set (dest) (reg))
+ because we don't know if the reg is live and has the same value at the
+ location of replacement. */
+ src1 = SET_SRC (p1);
+ src2 = SET_SRC (p2);
+ c1 = CONST_INT_P (src1);
+ c2 = CONST_INT_P (src2);
+ if (c1 && c2)
+ return dir_both;
+ else if (c2)
+ return dir_forward;
+ else if (c1)
+ return dir_backward;
+
+ return dir_none;
+}
+
+/* Merges directions A and B. */
+
+static enum replace_direction
+merge_dir (enum replace_direction a, enum replace_direction b)
+{
+ /* Implements the following table:
+ |bo fw bw no
+ ---+-----------
+ bo |bo fw bw no
+ fw |-- fw no no
+ bw |-- -- bw no
+ no |-- -- -- no. */
+
+ if (a == b)
+ return a;
+
+ if (a == dir_both)
+ return b;
+ if (b == dir_both)
+ return a;
+
+ return dir_none;
+}
+
-/* Return true if I1 and I2 are equivalent and thus can be crossjumped. */
+/* Examine I1 and I2 and return:
+ - dir_forward if I1 can be replaced by I2, or
+ - dir_backward if I2 can be replaced by I1, or
+ - dir_both if both are the case. */
-static bool
+static enum replace_direction
old_insns_match_p (int mode ATTRIBUTE_UNUSED, rtx i1, rtx i2)
{
rtx p1, p2;
/* Verify that I1 and I2 are equivalent. */
if (GET_CODE (i1) != GET_CODE (i2))
- return false;
+ return dir_none;
/* __builtin_unreachable() may lead to empty blocks (ending with
NOTE_INSN_BASIC_BLOCK). They may be crossjumped. */
if (NOTE_INSN_BASIC_BLOCK_P (i1) && NOTE_INSN_BASIC_BLOCK_P (i2))
- return true;
+ return dir_both;
p1 = PATTERN (i1);
p2 = PATTERN (i2);
if (GET_CODE (p1) != GET_CODE (p2))
- return false;
+ return dir_none;
/* If this is a CALL_INSN, compare register usage information.
If we don't check this on stack register machines, the two
@@ -991,15 +1072,15 @@
rtx n2 = find_reg_note (i2, REG_EH_REGION, 0);
if (!n1 && n2)
- return false;
+ return dir_none;
if (n1 && (!n2 || XEXP (n1, 0) != XEXP (n2, 0)))
- return false;
+ return dir_none;
if (!rtx_equal_p (CALL_INSN_FUNCTION_USAGE (i1),
CALL_INSN_FUNCTION_USAGE (i2))
|| SIBLING_CALL_P (i1) != SIBLING_CALL_P (i2))
- return false;
+ return dir_none;
}
#ifdef STACK_REGS
@@ -1028,15 +1109,15 @@
SET_HARD_REG_BIT (i2_regset, REGNO (XEXP (note, 0)));
if (!hard_reg_set_equal_p (i1_regset, i2_regset))
- return false;
+ return dir_none;
}
#endif
if (reload_completed
? rtx_renumbered_equal_p (p1, p2) : rtx_equal_p (p1, p2))
- return true;
+ return dir_both;
- return false;
+ return can_replace_by (i1, i2);
}
/* When comparing insns I1 and I2 in flow_find_cross_jump or
@@ -1063,18 +1144,32 @@
}
/* 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.
+ sequence that are either equivalent, or allow forward or backward
+ replacement. Store the first insns for that sequence in *F1 and *F2 and
+ return the sequence length.
+
+ DIR_P indicates the allowed replacement direction on function entry, and
+ the actual replacement direction on function exit. If NULL, only equivalent
+ sequences are allowed.
To simplify callers of this function, if the blocks match exactly,
store the head of the blocks in *F1 and *F2. */
int
-flow_find_cross_jump (basic_block bb1, basic_block bb2, rtx *f1, rtx *f2)
+flow_find_cross_jump (basic_block bb1, basic_block bb2, rtx *f1, rtx *f2,
+ enum replace_direction *dir_p)
{
rtx i1, i2, last1, last2, afterlast1, afterlast2;
int ninsns = 0;
rtx p1;
+ enum replace_direction dir, last_dir, afterlast_dir;
+
+ if (dir_p)
+ dir = *dir_p;
+ else
+ dir = dir_both;
+ afterlast_dir = dir;
+ last_dir = afterlast_dir;
/* Skip simple jumps at the end of the blocks. Complex jumps still
need to be compared for equivalence, which we'll do below. */
@@ -1111,7 +1206,8 @@
if (i1 == BB_HEAD (bb1) || i2 == BB_HEAD (bb2))
break;
- if (!old_insns_match_p (0, i1, i2))
+ dir = merge_dir (dir, old_insns_match_p (0, i1, i2));
+ if (dir == dir_none || (!dir_p && dir != dir_both))
break;
merge_memattrs (i1, i2);
@@ -1123,6 +1219,8 @@
afterlast1 = last1, afterlast2 = last2;
last1 = i1, last2 = i2;
+ afterlast_dir = last_dir;
+ last_dir = dir;
p1 = PATTERN (i1);
if (!(GET_CODE (p1) == USE || GET_CODE (p1) == CLOBBER))
ninsns++;
@@ -1136,7 +1234,7 @@
/* Don't allow the insn after a compare to be shared by
cross-jumping unless the compare is also shared. */
if (ninsns && reg_mentioned_p (cc0_rtx, last1) && ! sets_cc0_p (last1))
- last1 = afterlast1, last2 = afterlast2, ninsns--;
+ last1 = afterlast1, last2 = afterlast2, last_dir = afterlast_dir, ninsns--;
#endif
/* Include preceding notes and labels in the cross-jump. One,
@@ -1162,7 +1260,9 @@
*f2 = last2;
}
+ if (dir_p)
+ *dir_p = last_dir;
return ninsns;
}
/* Ignore notes. */
@@ -1226,7 +1326,7 @@
&& nehedges1 != nehedges2))
break;
- if (!old_insns_match_p (0, i1, i2))
+ if (old_insns_match_p (0, i1, i2) != dir_both)
break;
merge_memattrs (i1, i2);
@@ -1455,7 +1555,8 @@
rr.update_label_nuses = false;
for_each_rtx (&BB_END (bb1), replace_label, &rr);
- match = old_insns_match_p (mode, BB_END (bb1), BB_END (bb2));
+ match = (old_insns_match_p (mode, BB_END (bb1), BB_END (bb2))
+ == dir_both);
if (dump_file && match)
fprintf (dump_file,
"Tablejumps in bb %i and %i match.\n",
@@ -1477,7 +1578,7 @@
/* First ensure that the instructions match. There may be many outgoing
edges so this test is generally cheaper. */
- if (!old_insns_match_p (mode, BB_END (bb1), BB_END (bb2)))
+ if (old_insns_match_p (mode, BB_END (bb1), BB_END (bb2)) != dir_both)
return false;
/* Search the outgoing edges, ensure that the counts do match, find possible
@@ -1578,6 +1679,7 @@
int nmatch;
basic_block src1 = e1->src, src2 = e2->src;
basic_block redirect_to, redirect_from, to_remove;
+ enum replace_direction dir;
rtx newpos1, newpos2;
edge s;
edge_iterator ei;
@@ -1633,7 +1735,8 @@
return false;
/* ... and part the second. */
- nmatch = flow_find_cross_jump (src1, src2, &newpos1, &newpos2);
+ dir = dir_forward;
+ nmatch = flow_find_cross_jump (src1, src2, &newpos1, &newpos2, &dir);
/* Don't proceed with the crossjump unless we found a sufficient number
of matching instructions or the 'from' block was totally matched
--- gcc/ifcvt.c (revision 170556)
+++ gcc/ifcvt.c (working copy)
@@ -476,7 +476,8 @@ cond_exec_process_if_block (ce_if_block_
/* Look for matching sequences at the head and tail of the two blocks,
and limit the range of insns to be converted if possible. */
n_matching = flow_find_cross_jump (then_bb, else_bb,
- &then_first_tail, &else_first_tail);
+ &then_first_tail, &else_first_tail,
+ NULL);
if (then_first_tail == BB_HEAD (then_bb))
then_start = then_end = NULL_RTX;
if (else_first_tail == BB_HEAD (else_bb))
--- gcc/basic-block.h (revision 170556)
+++ gcc/basic-block.h (working copy)
@@ -803,9 +803,12 @@ extern bool purge_dead_edges (basic_bloc
extern void find_many_sub_basic_blocks (sbitmap);
extern void rtl_make_eh_edge (sbitmap, basic_block, rtx);
+enum replace_direction { dir_none, dir_forward, dir_backward, dir_both };
+
/* In cfgcleanup.c. */
extern bool cleanup_cfg (int);
-extern int flow_find_cross_jump (basic_block, basic_block, rtx *, rtx *);
+extern int flow_find_cross_jump (basic_block, basic_block, rtx *, rtx *,
+ enum replace_direction*);
extern int flow_find_head_matching_sequence (basic_block, basic_block,
rtx *, rtx *, int);
