Re: [rust-dev] How do I pass -march down to llvm from rustc?

2014-03-24 Thread Alex Crichton
You are right in that the __morestack function is a requirement from enabling segmented stacks in LLVM. While we no longer use truly segmented stacks, we still use the segmented stack prologue in order to detect stack overflow. This is a crucial piece of infrastructure for rust code used to ensure

Re: [rust-dev] How do I pass -march down to llvm from rustc?

2014-03-23 Thread Vladimir Pouzanov
Nevermind, I lost -O somewhere in between copying and pasting command line flags. Optimised version doesn't have any morestack references (which is strange concept though). On Sun, Mar 23, 2014 at 5:44 PM, Vladimir Pouzanov farcal...@gmail.comwrote: Figured out I can use --target

Re: [rust-dev] How do I pass -march down to llvm from rustc?

2014-03-23 Thread Vladimir Pouzanov
So it doesn't work in the end. rustc --emit bc with flags set for cortex-m0 provides exact same bc with only difference in target triple (which makes perfect sense) However, replacing llc step with rustc --emit asm provides a different assembler file, which requires __morestack. Should I expect

Re: [rust-dev] How do I pass -march down to llvm from rustc?

2014-03-23 Thread Corey Richardson
No. See https://github.com/mozilla/rust/pull/8955 and https://github.com/mozilla/rust/issues/11871 for discussion. You can stub out morestack but that won't remove the stack size checks. It's sanest to just compile the IR yourself (the stack checking is a target-specific machine pass, which is why

Re: [rust-dev] How do I pass -march down to llvm from rustc?

2014-03-23 Thread Vladimir Pouzanov
Thanks for links to bugs. Is there anything to read on the whole morestack thing? I thought that it's connected to segmented stacks that are (are they?) going away. It seems that I can use #[no_split_stack] before each and every function to generate a valid freestanding binary. If I just could