Different error outputs for rustup and source built rustc

compiler
1

This problem arose when I was trying to fix the issue presented on this rust issue page. Here is the source code:

fn main() {
    let (a, b) = get_pair();
}

fn get_pair() -> (f64, f64) {
    (0.0, 0.0)
}

When I try to compile the above code with SSE2 register disabled, the compilers built from source and rustup behave differently even when they are the same version.

d50032309@ptlaby31:~$ rust_install_temp/bin/rustc -C target-feature=-sse2 --allow warnings issue65844.rs # this is the rustc built from source
rustc: /home/d50032309/rust/src/llvm-project/llvm/lib/Target/X86/X86FloatingPoint.cpp:318: unsigned int getFPReg(const llvm::MachineOperand&): Assertion `Reg >= X86::FP0 && Reg <= X86::FP6 && "Expected FP register!"' failed.
Aborted (core dumped)
d50032309@ptlaby31:~$ .cargo/bin/rustc -C target-feature=-sse2 --allow warnings issue65844.rs # This is the same version of rustc, built from rustup
error: <unknown>:0:0: in function _ZN10issue658448get_pair17h1ac16997cb4aec1eE { double, double } (): SSE2 register return with SSE2 disabled

error: aborting due to previous error

In config.toml, I have set optimize=false and assertions=false, but the compiler still throws an assertion failure. What would be the problem here?

2

The error is coming from LLVM, so it is likely due to LLVM version difference.

3

llvm versions are actually the same on my end. In fact, any version of llvm&rustc built from source (after 05-2023) gives

rustc: /home/d50032309/rust/src/llvm-project/llvm/lib/Target/X86/X86FloatingPoint.cpp:318: unsigned int getFPReg(const llvm::MachineOperand&): Assertion `Reg >= X86::FP0 && Reg <= X86::FP6 && "Expected FP register!"' failed.
Aborted (core dumped)

And that built from rustup gives

error: <unknown>:0:0: in function _ZN10issue658448get_pair17h1ac16997cb4aec1eE { double, double } (): SSE2 register return with SSE2 disabled

error: aborting due to previous error

Is anyone experiencing this issue as well? I am wondering whether this is an issue that might need fixing, therefore it would be great if someone can try and reproduce it.