https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111403
Guo Jie <guojie at loongson dot cn> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |guojie at loongson dot cn
--- Comment #2 from Guo Jie <guojie at loongson dot cn> ---
It seems that “omp simd reduction” cannot collaborate well with “loop peeling”,
which will result in a probability error in this test case.
LoongArch tree vect pass dump:
# “omp simd” temporary arrays.
struct S D.3833[8];
struct S D.3832[8];
...
# prologue loop.
<bb 20> [local count: 723433550]:
MEM <struct S[32]> [(struct S *)&D.3832][0].s = 0;
_44 = D.3832[0].s;
_41 = (long unsigned int) i_1;
_58 = _41 * 4;
_59 = a_18(D) + _58;
_60 = _59->s;
_61 = _44 + _60;
D.3832[0].s = _61;
_64 = D.3833[0].s;
_65 = D.3832[0].s;
_66 = _64 + _65;
D.3833[0].s = _66; # Save temporary reduction results.
MEM <struct S[32]> [(struct S *)&D.3832][0].s = _66;
_69 = b_28(D) + _58;
_70 = MEM <struct S[32]> [(const struct S &)&D.3832][0].s;
_69->s = _70;
i_72 = i_1 + 1;
ivtmp_73 = ivtmp_2 - 1;
ivtmp_78 = ivtmp_77 + 1;
if (ivtmp_78 < prolog_loop_niters.42_7)
goto <bb 21>; [85.71%]
else
goto <bb 18>; [14.29%]
<bb 21> [local count: 620085901]:
goto <bb 20>; [100.00%]
# vector body loop.
<bb 5> [local count: 118111599]:
# i_48 = PHI <i_30(12), i_79(22)>
# ivtmp_55 = PHI <ivtmp_45(12), ivtmp_81(22)>
# vectp_a.50_126 = PHI <vectp_a.50_127(12), vectp_a.51_123(22)>
# vectp_b.58_158 = PHI <vectp_b.58_159(12), vectp_b.59_155(22)>
# ivtmp_161 = PHI <ivtmp_162(12), 0(22)>
MEM <vector(8) int> [(struct S *)&D.3832] = { 0, 0, 0, 0, 0, 0, 0, 0 };
_16 = (long unsigned int) i_48;
_17 = _16 * 4;
_19 = a_18(D) + _17;
vect__20.52_128 = MEM <vector(8) int> [(int *)vectp_a.50_126];
_20 = _19->s;
MEM <vector(8) int> [(int *)&D.3832] = vect__20.52_128;
vect__24.54_131 = MEM <vector(8) int> [(int *)&D.3833]; # Wrong value.
...
vect__26.56_133 = vect__20.52_128 + vect__24.54_131;
...
if (ivtmp_162 < bnd.44_109)
goto <bb 12>; [0.00%]
else
goto <bb 25>; [100.00%]
...
The temporary reduction result of “prologue loop” is only stored in D.3833[0],
and all other elements of D.3833 are 0. Therefore, only the first element of
vect__26.56_133 accumulates the scalar reduction result of “prologue loop”.
I think the reasonable solution should be to broadcast the scalar reduction
result of “prologue loop” to all elements of D.3833.
