https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97832
--- Comment #23 from Hongtao.liu <crazylht at gmail dot com> --- > the blends do not look like no-ops so I wonder if this is really computing > the same thing ... (it swaps lane 0 from the two loads from x but not the > stores) They're computing the same thing since we also do the same "permutation" for the invariants: f_re and f_imm, can we eliminate that in the vectorizer? _232 = {f_im_36, f_im_36, f_im_36, f_im_36}; _231 = {f_im_36, f_re_35, f_re_35, f_re_35}; ------- here _216 = {f_re_35, f_re_35, f_re_35, f_re_35}; _215 = {f_re_35, f_im_36, f_im_36, f_im_36}; ------ and here. ivtmp.36_221 = (unsigned long) y_41(D); ivtmp.38_61 = (unsigned long) x_33(D); <bb 4> [local count: 214748368]: # ivtmp.32_66 = PHI <ivtmp.32_65(4), 0(3)> # ivtmp.36_64 = PHI <ivtmp.36_63(4), ivtmp.36_221(3)> # ivtmp.38_220 = PHI <ivtmp.38_60(4), ivtmp.38_61(3)> # DEBUG c => NULL # DEBUG k => 0 # DEBUG BEGIN_STMT # DEBUG BEGIN_STMT # DEBUG D#78 => D#79 * 8 # DEBUG D#77 => x_33(D) + D#78 _62 = (void *) ivtmp.38_220; vect_x_im_61.13_228 = MEM <const vector(4) double> [(const double *)_62]; vect_x_im_61.14_226 = MEM <const vector(4) double> [(const double *)_62 + 32B]; vect_x_re_55.15_225 = VEC_PERM_EXPR <vect_x_im_61.14_226, vect_x_im_61.13_228, { 0, 5, 6, 7 }>; vect_x_re_55.23_209 = VEC_PERM_EXPR <vect_x_im_61.13_228, vect_x_im_61.14_226, { 0, 5, 6, 7 }>; # DEBUG D#76 => *D#77 # DEBUG x_re => D#76 # DEBUG BEGIN_STMT # DEBUG D#74 => (long unsigned int) D#75 # DEBUG D#73 => D#74 * 8 # DEBUG D#72 => x_33(D) + D#73 # DEBUG D#71 => *D#72 # DEBUG x_im => D#71 # DEBUG BEGIN_STMT # DEBUG D#70 => y_41(D) + D#78 _59 = (void *) ivtmp.36_64; vect_y_re_63.9_235 = MEM <vector(4) double> [(double *)_59]; vect_y_re_63.10_233 = MEM <vector(4) double> [(double *)_59 + 32B]; vect__42.18_219 = .FMA (vect_x_im_61.13_228, _232, vect_y_re_63.10_233); vect_y_re_69.17_222 = .FNMA (vect_x_re_55.15_225, _231, vect_y_re_63.9_235); vect_y_re_69.25_206 = .FNMA (vect_x_re_55.23_209, _215, vect_y_re_69.17_222); vect_y_re_69.25_205 = .FNMA (_216, vect_x_im_61.14_226, vect__42.18_219);