Bug 14257 – ICE(backend/go.c) with large static foreach

DMD fails to optimize code like the following, when foreach aggregate is staticIota!(0, x >= 100). Reduced test case: template TypeTuple(TList...) { alias TypeTuple = TList; } package template staticIota(int beg, int end) { static if (beg + 1 >= end) { static if (beg >= end) { alias staticIota = TypeTuple!(); } else { alias staticIota = TypeTuple!(+beg); } } else { enum mid = beg + (end - beg) / 2; alias staticIota = TypeTuple!(staticIota!(beg, mid), staticIota!(mid, end)); } } void test() { int row; foreach (s; staticIota!(0, 100)) { if (++row) row = 0; } } $ dmd -O -c test.d Internal error: backend/go.c 242

Created attachment 1490 workaround this is caused by the same bug that causes Issue #14214: too many "code comma expressions". i'm almost sure that both bugs triggered by the same code path, as i did a quick workaround for #14214 (not failing on processing too many OPcomma blocks), and it fixes this bug too. yet i'm not familiar with codegen, so i will not mark this as duplicate, as this need further investigation from a person with codegen/optimizer knowledge. i attached the workaround for those who want to dive into optimizer. it degrades optimizing quality in such pathological cases, but it at least allows optimizer to process other code.

ah, and changed the hardware, as this is general arch-independent optimizer bug.

I cannot reproduce this. The code compiles successfully now.