Inline asm: The "=m" constraint causes an illegal instruction error

[gnutick]

Hi!

Rust ends with an illegal instruction error when I try to compile this:

let mut c: u64;
asm!("" : "=m" (c));

Maybe because it generates wrong LLVM IR.

Rust/LLVM IR:

%1 = call i64 asm "", "=m,~{dirflag},~{fpsr},~{flags}"(), !srcloc !0
store i64 %1, i64* %c

Clang/LLVM IR:

call void asm "", "=*m,~{dirflag},~{fpsr},~{flags}"(i64* %c) #1, !srcloc !1

Meta

rustc --version --verbose:
rustc 1.1.0-dev (2214860 2015-04-24) (built 2015-04-25)
binary: rustc
commit-hash: 2214860
commit-date: 2015-04-24
build-date: 2015-04-25
host: x86_64-unknown-linux-gnu
release: 1.1.0-dev

clang --version:
Ubuntu clang version 3.6.0-2ubuntu1 (tags/RELEASE_360/final) (based on LLVM 3.6.0)
Target: x86_64-pc-linux-gnu
Thread model: posix

[nagisa]

Citing @huonw:

Our constraints do not duplicate GCC; its just that we implement several of the same constraints GCC supports.

Anyway, duplicate of #16383

[steveklabnik]

Yes, this is a duplicate. Thanks though!