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Auto merge of #86416 - Amanieu:asm_clobber_only, r=nagisa

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Add clobber-only register classes for asm!

These are needed to properly express a function call ABI using a clobber
list, even though we don't support passing actual values into/out of
these registers.
This commit is contained in:
bors 2021-07-11 01:06:58 +00:00
commit 99f8efec46
11 changed files with 273 additions and 62 deletions
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16
compiler/rustc_ast_lowering/src/asm.rs
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@ -199,6 +199,22 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
}
);
// Some register classes can only be used as clobbers. This
// means that we disallow passing a value in/out of the asm and
// require that the operand name an explicit register, not a
// register class.
if reg_class.is_clobber_only(asm_arch.unwrap())
&& !(is_clobber && matches!(reg, asm::InlineAsmRegOrRegClass::Reg(_)))
{
let msg = format!(
"register class `{}` can only be used as a clobber, \
not as an input or output",
reg_class.name()
);
sess.struct_span_err(op_sp, &msg).emit();
continue;
}
if !is_clobber {
// Validate register classes against currently enabled target
// features. We check that at least one type is available for