https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116520
Andi Kleen <andi-gcc at firstfloor dot org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Summary|incorrect |Multiple condition lead to
| |missing vectorization due
| |to missing early break
--- Comment #1 from Andi Kleen <andi-gcc at firstfloor dot org> ---
const unsigned char *search_line_fast2 (const unsigned char *s,
const unsigned char *end)
{
while (s < end) {
if (*s == '\n' || *s == '\r' || *s == '\\' || *s == '?')
break;
s++;
}
return s;
}
compiled with -march=skylake-avx512 -fopt-info-all gives
../gcc/gcc/testsuite/gcc.dg/vect/vect-switch-search-line-fast.c:9:12: missed:
couldn't vectorize loop
../gcc/gcc/testsuite/gcc.dg/vect/vect-switch-search-line-fast.c:9:12: missed:
not vectorized: unsupported control flow in loop.
due to this:
/* Check if we have any control flow that doesn't leave the loop. */
class loop *v_loop = loop->inner ? loop->inner : loop;
basic_block *bbs = get_loop_body (v_loop);
for (unsigned i = 0; i < v_loop->num_nodes; i++)
if (EDGE_COUNT (bbs[i]->succs) != 1
&& (EDGE_COUNT (bbs[i]->succs) != 2
|| !loop_exits_from_bb_p (bbs[i]->loop_father, bbs[i])))
{
free (bbs);
return opt_result::failure_at (vect_location,
"not vectorized:"
" unsupported control flow in loop.\n");
}
But the control flow clearly leaves the loop.
At the gimple level it gives code like
<bb 8> [local count: 110211694]:
<bb 3> [local count: 1044213920]:
# s_15 = PHI <s_9(9), s_6(D)(8)>
_1 = *s_15;
if (_1 > 63)
goto <bb 11>; [50.00%]
else
goto <bb 4>; [50.00%]
<bb 11> [local count: 522106960]:
goto <bb 5>; [100.00%]
<bb 4> [local count: 522106960]:
_14 = (int) _1;
_17 = 9223372036854785024 >> _14;
_18 = _17 & 1;
_19 = _18 == 0;
_12 = ~_19;
<bb 5> [local count: 1044213920]:
# prephitmp_4 = PHI <_12(4), 0(11)>
_10 = _1 == 92;
_13 = prephitmp_4 | _10;
if (_13 != 0)
goto <bb 12>; [8.03%]
else
goto <bb 6>; [91.97%]
<bb 12> [local count: 83800317]:
# s_5 = PHI <s_15(5)>
goto <bb 7>; [100.00%]
<bb 6> [local count: 960413605]:
s_9 = s_15 + 1;
if (end_7(D) > s_9)
goto <bb 9>; [97.25%]
else
goto <bb 13>; [2.75%]
<bb 13> [local count: 26411378]:
# s_20 = PHI <s_9(6)>
goto <bb 7>; [100.00%]
<bb 9> [local count: 934002227]:
goto <bb 3>; [100.00%]
which seems to come from if to switch and then switch expansion?
