search for: d68076

Hi Paul, thanks for your comments. This is PR37240 (https://bugs.llvm.org/show_bug.cgi?id=37240). I suspect this problem affects all targets; your patch D68076 would address it only for AArch64. Although I would suggest you do some careful measurements to determine the runtime performance effect, to decide whether this is acceptable. Yes, in principle the problem that instruction scheduling is dependent on the presence of cfi instruction should affect mo...

Hi Vedant, thanks for your answer and sorry for the late response. It seems like D68076 might not address the underlying issue here (e.g. it probably doesn't improve the situation for projects using `-g -fno-unwind-tables`?). Yes, D68075 is a somewhat conservative patch that aligns the behaviour on AArch64 (for GNU targets) that leads to consistent generated assembly. As you said...

...without default unwind tables and found an average difference of 0.5 to 1 instruction. Other architectures such as x86 do exactly this and therefore don't face the issue. The following patch on Phabricator introduces the said change: https://reviews.llvm.org/D68076 2. Postpone insertion of CFI instructions until after instruction scheduling. This would require a new pass running after instruction scheduling that inserts CFI instructions if needed. The downside I see is increased compile-time and probably some code duplication with frame lowe...