x86_64 asm: Build error when using r[8-15]b · Issue #485 · rust-lang/rustc_codegen_gcc (original) (raw)

The following code passes build with cg_llvm, but fails with cg_gcc.

#[inline(never)] pub unsafe fn f() { core::arch::asm!( "", out("al") _, out("bl") _, out("cl") _, out("dl") _, out("sil") _, out("dil") _, // out("bpl") _, // frame pointer out("r8b") _, out("r9b") _, out("r10b") _, out("r11b") _, out("r12b") _, out("r13b") _, out("r14b") _, out("r15b") _, ); }

The following is the error message when building with cg_gcc.

libgccjit.so: error: unknown register name 'r15b' in 'asm'
libgccjit.so: error: unknown register name 'r14b' in 'asm'
libgccjit.so: error: unknown register name 'r13b' in 'asm'
libgccjit.so: error: unknown register name 'r12b' in 'asm'
libgccjit.so: error: unknown register name 'r11b' in 'asm'
libgccjit.so: error: unknown register name 'r10b' in 'asm'
libgccjit.so: error: unknown register name 'r9b' in 'asm'
libgccjit.so: error: unknown register name 'r8b' in 'asm'
error: could not copy "/app/output.example.fb61ce7e3f5ff483-cgu.0.rcgu.s" to "/app/output.s": No such file or directory (os error 2)

playground

I could reproduce this with both playground and the latest master branch (75f0ab5).

Reference: https://doc.rust-lang.org/nightly/reference/inline-assembly.html#register-operands

Architecture	Register class	Registers	LLVM constraint code
x86-64	reg_byte*	al, bl, cl, dl, sil, dil, bpl, r[8-15]b	q