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 rustc to generate freestanding code given some additional options? On Sun, Mar 23, 2014 at 5:55 PM, Vladimir Pouzanov <farcal...@gmail.com>wrote: > 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.com>wrote: > >> Figured out I can use --target thumbv6m-linux-eabi, which implies >> -mthumb. Now the problem is that if I use >> >> rustc --target thumbv6m-linux-eabi -O --emit obj main.rs -o main.o >> >> instead of three-step process I mentioned before, I get a valid object >> file for cortex-m0, but functions have big prologues and symbol table is >> much bigger: >> >> U STACK_LIMIT >> U _GLOBAL_OFFSET_TABLE_ >> 00000000 D _ZN20_rust_crate_map_main16ad67637f924a5c794v0.0E >> 00000008 r _ZN2hw11GPIO_PIN_NO20hb0b70c1482b61788Gaa4v0.0E >> 00000000 r _ZN2hw12GPIO_DIR_REG20hb0b70c1482b61788yaa4v0.0E >> 00000004 r _ZN2hw12GPIO_REG_VAL20hb0b70c1482b61788Caa4v0.0E >> 00000078 t _ZN4main10__rust_abiE >> 00000000 t _ZN4wait20h53ffb23463e08f19Maa4v0.0E >> U __aeabi_unwind_cpp_pr0 >> U __morestack >> 0000004c T main >> >> vs. >> >> 00000000 D _ZN23_rust_crate_map_main.c016ad67637f924a5c794v0.0E >> 00000000 T main >> >> in the initial version. Also, I now need to provide __morestack (no idea >> what's that about). >> >> >> On Sun, Mar 23, 2014 at 5:17 PM, Alex Crichton <a...@crichton.co> wrote: >> >>> You should be able to assemble standalone objects for any triple >>> through rustc itself, you'll likely have to specify a different linker >>> or assembler though: >>> >>> rustc foo.rs --target arm-non-linux-gnueabi \ >>> -C linker=arm-non-linux-gnueabi-ld \ >>> -C ar=arm-non-linux-gnueabi-ar >>> >>> As you discovered, you can pass through arguments to LLVM via the "-C >>> llvm-args=foo" command line option to rustc. If you get complaints >>> that it's an unknown command line argument, it's LLVM telling you >>> those complaints, not rustc. >>> >>> On Sun, Mar 23, 2014 at 8:54 AM, Vladimir Pouzanov <farcal...@gmail.com> >>> wrote: >>> > I'm trying to experiment with rust and some embedded code. Currently I >>> have >>> > to do a three-pass compilation: >>> > >>> > rustc --target arm-linux-eabi -O --emit bc main.rs -o main.bc >>> > llc -mtriple arm-none-eabi -march=thumb -mcpu=cortex-m0 main.bc -o >>> main.s >>> > arm-none-linux-gnueabi-as main.s -o main.o >>> > >>> > First, I'm not sure how relevant is --target flag for rustc. I seems to >>> > change target datalayout/triple in generated bc, but that should be >>> > overriden by llc -mtriple anyway, right? >>> > >>> > Second, I can pass -Ctarget-cpu=cortex-m0, but I cannot pass down >>> > -march=thumb, tried this way: -Cllvm-args='--march=thumb', failed with >>> > "rustc: Unknown command line argument '--march=thumb'". >>> > >>> > Any hints on how can I drop explicit llc and as steps here? >>> > >>> > -- >>> > Sincerely, >>> > Vladimir "Farcaller" Pouzanov >>> > http://farcaller.net/ >>> > >>> > _______________________________________________ >>> > Rust-dev mailing list >>> > Rust-dev@mozilla.org >>> > https://mail.mozilla.org/listinfo/rust-dev >>> > >>> >> >> >> >> -- >> Sincerely, >> Vladimir "Farcaller" Pouzanov >> http://farcaller.net/ >> > > > > -- > Sincerely, > Vladimir "Farcaller" Pouzanov > http://farcaller.net/ > -- Sincerely, Vladimir "Farcaller" Pouzanov http://farcaller.net/
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