https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81884
Richard Biener <rguenth at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Status|UNCONFIRMED |ASSIGNED Last reconfirmed| |2017-08-18 Component|c++ |tree-optimization Assignee|unassigned at gcc dot gnu.org |rguenth at gcc dot gnu.org Ever confirmed|0 |1 --- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> --- Confirmed. Mine. DSE is optimizing void initialize() () { long unsigned int SR.19; struct value_t D.2321; struct X * x.0_1; struct X * x.3_4; <bb 2> [100.00%]: x.0_1 = x; x.0_1->arr[0] = 11; x.0_1->arr[1] = 12; MEM[(struct X *)x.0_1] = 10; x.3_4 = x; x.3_4->arr[2] = 13; x.3_4->arr[3] = 14; return; to __attribute__((noinline, noclone)) void initialize() () { long unsigned int SR.19; struct value_t D.2321; struct X * x.0_1; struct X * x.3_4; <bb 2> [100.00%]: x.0_1 = x; MEM[(struct X *)x.0_1] = 10; x.3_4 = x; x.3_4->arr[2] = 13; x.3_4->arr[3] = 14; return; so it appears that it treats the "aggregate" assignment as a must-def.