https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98598
--- Comment #2 from Jiangning Liu <jiangning.liu at amperecomputing dot com> --- Loop distribution can only handle very simple case. If the inner loop has complicated control flow and other memory accesses with loop-carried dependence, it would be hard to handle it. For example, int foo (int n, int m, A *pa) { int sum; for (int i = 0; i < n; i++) { for (int j = 0; j < m; j++) { sum += pa[j].pb->pc->val; // each value is repeatedly loaded "n" times sum = sum % 7; } sum = sum % 13; } return sum; } Alternatively, we can detect "invariant" dependent memory loads for the nested loops with alias conflict checked. If the outer loop is hot enough, we could have a chance to "hoist" them to create cache. As for temp storage, is it a gcc's rule of thumb not to introduce temp storage on heap, or it is just gcc doesn't have it yet and we want to have it?