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Rollup merge of #119365 - nbdd0121:asm-goto, r=Amanieu

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Add asm goto support to `asm!`

Tracking issue: #119364

This PR implements asm-goto support, using the syntax described in "future possibilities" section of [RFC2873](https://rust-lang.github.io/rfcs/2873-inline-asm.html#asm-goto).

Currently I have only implemented the `label` part, not the `fallthrough` part (i.e. fallthrough is implicit). This doesn't reduce the expressive though, since you can use label-break to get arbitrary control flow or simply set a value and rely on jump threading optimisation to get the desired control flow. I can add that later if deemed necessary.

r? ``@Amanieu``
cc ``@ojeda``
This commit is contained in:
Matthias Krüger 2024-03-08 08:19:17 +01:00 • committed by GitHub
commit d774fbea7c
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76 changed files with 857 additions and 200 deletions
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27
compiler/rustc_ast_lowering/src/asm.rs
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@ -3,9 +3,9 @@ use crate::{ImplTraitContext, ImplTraitPosition, ParamMode, ResolverAstLoweringE
use super::errors::{
AbiSpecifiedMultipleTimes, AttSyntaxOnlyX86, ClobberAbiNotSupported,
InlineAsmUnsupportedTarget, InvalidAbiClobberAbi, InvalidAsmTemplateModifierConst,
InvalidAsmTemplateModifierRegClass, InvalidAsmTemplateModifierRegClassSub,
InvalidAsmTemplateModifierSym, InvalidRegister, InvalidRegisterClass, RegisterClassOnlyClobber,
RegisterConflict,
InvalidAsmTemplateModifierLabel, InvalidAsmTemplateModifierRegClass,
InvalidAsmTemplateModifierRegClassSub, InvalidAsmTemplateModifierSym, InvalidRegister,
InvalidRegisterClass, RegisterClassOnlyClobber, RegisterConflict,
};
use super::LoweringContext;
@ -237,6 +237,18 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
}
}
}
InlineAsmOperand::Label { block } => {
if !self.tcx.features().asm_goto {
feature_err(
sess,
sym::asm_goto,
*op_sp,
"label operands for inline assembly are unstable",
)
.emit();
}
hir::InlineAsmOperand::Label { block: self.lower_block(block, false) }
}
};
(op, self.lower_span(*op_sp))
})
@ -296,6 +308,12 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
op_span: op_sp,
});
}
hir::InlineAsmOperand::Label { .. } => {
self.dcx().emit_err(InvalidAsmTemplateModifierLabel {
placeholder_span,
op_span: op_sp,
});
}
}
}
}
@ -335,7 +353,8 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
hir::InlineAsmOperand::Const { .. }
| hir::InlineAsmOperand::SymFn { .. }
| hir::InlineAsmOperand::SymStatic { .. } => {
| hir::InlineAsmOperand::SymStatic { .. }
| hir::InlineAsmOperand::Label { .. } => {
unreachable!("{op:?} is not a register operand");
}
};