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Implement asm! interpolate #156719

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8 changes: 7 additions & 1 deletion compiler/rustc_ast/src/ast.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -2841,6 +2841,9 @@ pub enum InlineAsmOperand {
Const {
anon_const: AnonConst,
},
Interpolate {
anon_const: AnonConst,
},
Sym {
sym: InlineAsmSym,
},
Expand All @@ -2856,7 +2859,10 @@ impl InlineAsmOperand {
| Self::Out { reg, .. }
| Self::InOut { reg, .. }
| Self::SplitInOut { reg, .. } => Some(reg),
Self::Const { .. } | Self::Sym { .. } | Self::Label { .. } => None,
Self::Const { .. }
| Self::Interpolate { .. }
| Self::Sym { .. }
| Self::Label { .. } => None,
}
}
}
Expand Down
20 changes: 16 additions & 4 deletions compiler/rustc_ast_lowering/src/asm.rs
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Expand Up @@ -13,10 +13,10 @@ use super::LoweringContext;
use super::errors::{
AbiSpecifiedMultipleTimes, AttSyntaxOnlyX86, ClobberAbiNotSupported,
InlineAsmUnsupportedTarget, InvalidAbiClobberAbi, InvalidAsmTemplateModifierConst,
InvalidAsmTemplateModifierLabel, InvalidAsmTemplateModifierRegClass,
InvalidAsmTemplateModifierRegClassSub, InvalidAsmTemplateModifierSym, InvalidRegister,
InvalidRegisterClass, RegisterClassOnlyClobber, RegisterClassOnlyClobberStable,
RegisterConflict,
InvalidAsmTemplateModifierInterpolate, InvalidAsmTemplateModifierLabel,
InvalidAsmTemplateModifierRegClass, InvalidAsmTemplateModifierRegClassSub,
InvalidAsmTemplateModifierSym, InvalidRegister, InvalidRegisterClass, RegisterClassOnlyClobber,
RegisterClassOnlyClobberStable, RegisterConflict,
};
use crate::{AllowReturnTypeNotation, ImplTraitContext, ImplTraitPosition, ParamMode};

Expand Down Expand Up @@ -199,6 +199,11 @@ impl<'hir> LoweringContext<'_, 'hir> {
InlineAsmOperand::Const { anon_const } => hir::InlineAsmOperand::Const {
anon_const: self.lower_const_block(anon_const),
},
InlineAsmOperand::Interpolate { anon_const } => {
hir::InlineAsmOperand::Interpolate {
anon_const: self.lower_const_block(anon_const),
}
}
InlineAsmOperand::Sym { sym } => {
let static_def_id = self
.get_partial_res(sym.id)
Expand Down Expand Up @@ -285,6 +290,12 @@ impl<'hir> LoweringContext<'_, 'hir> {
op_span: op_sp,
});
}
hir::InlineAsmOperand::Interpolate { .. } => {
self.dcx().emit_err(InvalidAsmTemplateModifierInterpolate {
placeholder_span,
op_span: op_sp,
});
}
hir::InlineAsmOperand::SymFn { .. }
| hir::InlineAsmOperand::SymStatic { .. } => {
self.dcx().emit_err(InvalidAsmTemplateModifierSym {
Expand Down Expand Up @@ -354,6 +365,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
| hir::InlineAsmOperand::SplitInOut { .. } => (true, true),

hir::InlineAsmOperand::Const { .. }
| hir::InlineAsmOperand::Interpolate { .. }
| hir::InlineAsmOperand::SymFn { .. }
| hir::InlineAsmOperand::SymStatic { .. }
| hir::InlineAsmOperand::Label { .. } => {
Expand Down
10 changes: 10 additions & 0 deletions compiler/rustc_ast_lowering/src/errors.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -258,6 +258,16 @@ pub(crate) struct InvalidAsmTemplateModifierConst {
pub op_span: Span,
}

#[derive(Diagnostic)]
#[diag("asm template modifiers are not allowed for `interpolate` arguments")]
pub(crate) struct InvalidAsmTemplateModifierInterpolate {
#[primary_span]
#[label("template modifier")]
pub placeholder_span: Span,
#[label("argument")]
pub op_span: Span,
}

#[derive(Diagnostic)]
#[diag("asm template modifiers are not allowed for `sym` arguments")]
pub(crate) struct InvalidAsmTemplateModifierSym {
Expand Down
6 changes: 6 additions & 0 deletions compiler/rustc_ast_pretty/src/pprust/state.rs
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Expand Up @@ -1665,6 +1665,7 @@ impl<'a> State<'a> {
matches!(reg, InlineAsmRegOrRegClass::Reg(_))
}
InlineAsmOperand::Const { .. }
| InlineAsmOperand::Interpolate { .. }
| InlineAsmOperand::Sym { .. }
| InlineAsmOperand::Label { .. } => false,
}
Expand Down Expand Up @@ -1805,6 +1806,11 @@ impl<'a> State<'a> {
s.space();
s.print_expr(&anon_const.value, FixupContext::default());
}
InlineAsmOperand::Interpolate { anon_const } => {
s.word("interpolate");
s.space();
s.print_expr(&anon_const.value, FixupContext::default());
}
InlineAsmOperand::Sym { sym } => {
s.word("sym");
s.space();
Expand Down
1 change: 1 addition & 0 deletions compiler/rustc_borrowck/src/lib.rs
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Expand Up @@ -965,6 +965,7 @@ impl<'a, 'tcx> ResultsVisitor<'tcx, Borrowck<'a, 'tcx>> for MirBorrowckCtxt<'a,
}
}
InlineAsmOperand::Const { value: _ }
| InlineAsmOperand::Interpolate { value: _ }
| InlineAsmOperand::SymFn { value: _ }
| InlineAsmOperand::SymStatic { def_id: _ }
| InlineAsmOperand::Label { target_index: _ } => {}
Expand Down
1 change: 1 addition & 0 deletions compiler/rustc_borrowck/src/polonius/legacy/loan_invalidations.rs
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Expand Up @@ -195,6 +195,7 @@ impl<'a, 'tcx> Visitor<'tcx> for LoanInvalidationsGenerator<'a, 'tcx> {
}
}
InlineAsmOperand::Const { value: _ }
| InlineAsmOperand::Interpolate { value: _ }
| InlineAsmOperand::SymFn { value: _ }
| InlineAsmOperand::SymStatic { def_id: _ }
| InlineAsmOperand::Label { target_index: _ } => {}
Expand Down
3 changes: 3 additions & 0 deletions compiler/rustc_codegen_cranelift/src/global_asm.rs
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Expand Up @@ -111,6 +111,9 @@ fn codegen_global_asm_inner<'tcx>(
GlobalAsmOperandRef::Const { ref string } => {
global_asm.push_str(string);
}
GlobalAsmOperandRef::Interpolate { string } => {
global_asm.push_str(string);
}
GlobalAsmOperandRef::SymFn { instance } => {
if cfg!(not(feature = "inline_asm_sym")) {
tcx.dcx().span_err(
Expand Down
20 changes: 19 additions & 1 deletion compiler/rustc_codegen_cranelift/src/inline_asm.rs
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Expand Up @@ -33,6 +33,9 @@ pub(crate) enum CInlineAsmOperand<'tcx> {
Const {
value: String,
},
Interpolate {
value: &'tcx str,
},
Symbol {
symbol: String,
},
Expand Down Expand Up @@ -104,6 +107,16 @@ pub(crate) fn codegen_inline_asm_terminator<'tcx>(
);
CInlineAsmOperand::Const { value }
}
InlineAsmOperand::Interpolate { ref value } => {
let (const_value, ty) = crate::constant::eval_mir_constant(fx, value);
let value = rustc_codegen_ssa::common::asm_interpolate_to_str(
fx.tcx,
span,
const_value,
fx.layout_of(ty),
);
CInlineAsmOperand::Interpolate { value }
}
InlineAsmOperand::SymFn { ref value } => {
if cfg!(not(feature = "inline_asm_sym")) {
fx.tcx
Expand Down Expand Up @@ -227,7 +240,9 @@ pub(crate) fn codegen_inline_asm_inner<'tcx>(
outputs.push((asm_gen.stack_slots_output[i].unwrap(), *out_place));
}
}
CInlineAsmOperand::Const { value: _ } | CInlineAsmOperand::Symbol { symbol: _ } => {}
CInlineAsmOperand::Const { value: _ }
| CInlineAsmOperand::Interpolate { value: _ }
| CInlineAsmOperand::Symbol { symbol: _ } => {}
}
}

Expand Down Expand Up @@ -585,6 +600,9 @@ impl<'tcx> InlineAssemblyGenerator<'_, 'tcx> {
CInlineAsmOperand::Const { ref value } => {
generated_asm.push_str(value);
}
CInlineAsmOperand::Interpolate { value } => {
generated_asm.push_str(value);
}
CInlineAsmOperand::Symbol { ref symbol } => {
if binary_format == BinaryFormat::Macho {
generated_asm.push('_');
Expand Down
19 changes: 19 additions & 0 deletions compiler/rustc_codegen_gcc/src/asm.rs
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Expand Up @@ -307,6 +307,10 @@ impl<'a, 'gcc, 'tcx> AsmBuilderMethods<'tcx> for Builder<'a, 'gcc, 'tcx> {
constants_len += string.len() + att_dialect as usize;
}

InlineAsmOperandRef::Interpolate { string } => {
constants_len += string.len() + att_dialect as usize;
}

InlineAsmOperandRef::SymFn { instance } => {
// FIXME(@Amanieu): Additional mangling is needed on
// some targets to add a leading underscore (Mach-O)
Expand Down Expand Up @@ -422,6 +426,10 @@ impl<'a, 'gcc, 'tcx> AsmBuilderMethods<'tcx> for Builder<'a, 'gcc, 'tcx> {
// processed in the previous pass
}

InlineAsmOperandRef::Interpolate { .. } => {
// processed in the previous pass
}

InlineAsmOperandRef::Label { .. } => {
// processed in the previous pass
}
Expand Down Expand Up @@ -515,6 +523,10 @@ impl<'a, 'gcc, 'tcx> AsmBuilderMethods<'tcx> for Builder<'a, 'gcc, 'tcx> {
template_str.push_str(string);
}

InlineAsmOperandRef::Interpolate { string } => {
template_str.push_str(string);

@Amanieu Amanieu Jun 3, 2026 •
edited by rustbot
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Same here, this needs the same escaping as the main template string.

View changes since the review

}

InlineAsmOperandRef::Label { label } => {
let label_gcc_index =
labels.iter().position(|&l| l == label).expect("wrong rust index");
Expand Down Expand Up @@ -921,6 +933,13 @@ impl<'gcc, 'tcx> AsmCodegenMethods<'tcx> for CodegenCx<'gcc, 'tcx> {
template_str.push_str(string);
}

GlobalAsmOperandRef::Interpolate { string } => {
// Interpolate operands get injected directly into the
// template. Note that we don't need to escape %
// here unlike normal inline assembly.
template_str.push_str(string);
}

GlobalAsmOperandRef::SymFn { instance } => {
let function = get_fn(self, instance);
self.add_used_function(function);
Expand Down
10 changes: 10 additions & 0 deletions compiler/rustc_codegen_llvm/src/asm.rs
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Expand Up @@ -208,6 +208,10 @@ impl<'ll, 'tcx> AsmBuilderMethods<'tcx> for Builder<'_, 'll, 'tcx> {
// Const operands get injected directly into the template
template_str.push_str(string);
}
InlineAsmOperandRef::Interpolate { string } => {
// Interpolate operands get injected directly into the template
template_str.push_str(string);
}
Comment on lines +211 to +214

@traviscross traviscross May 31, 2026 •
edited by rustbot
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What's the intended behavior of this?

fn zero(mut x: u64) -> u64 {
    unsafe {
        asm!("mov {0}, {1}", interpolate "$0", inout(reg) x,
             options(att_syntax));
    }
    x
}

View changes since the review

@Amanieu Amanieu Jun 3, 2026

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This absolutely needs to have $ escaped, just like a normal template string piece.

InlineAsmOperandRef::SymFn { .. }
| InlineAsmOperandRef::SymStatic { .. } => {
// Only emit the raw symbol name
Expand Down Expand Up @@ -409,6 +413,12 @@ impl<'tcx> AsmCodegenMethods<'tcx> for CodegenCx<'_, 'tcx> {
// here unlike normal inline assembly.
template_str.push_str(string);
}
GlobalAsmOperandRef::Interpolate { string } => {
// Interpolate operands get injected directly into the
// template. Note that we don't need to escape $
// here unlike normal inline assembly.
template_str.push_str(string);
}
GlobalAsmOperandRef::SymFn { instance } => {
let llval = self.get_fn(instance);
self.add_compiler_used_global(llval);
Expand Down
25 changes: 25 additions & 0 deletions compiler/rustc_codegen_ssa/src/base.rs
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Expand Up @@ -439,6 +439,31 @@ where
}
}
}
rustc_hir::InlineAsmOperand::Interpolate { ref anon_const } => {
match cx.tcx().const_eval_poly(anon_const.def_id.to_def_id()) {
Ok(const_value) => {
let ty =
cx.tcx().typeck_body(anon_const.body).node_type(anon_const.hir_id);
let string = common::asm_interpolate_to_str(
cx.tcx(),
*op_sp,
const_value,
cx.layout_of(ty),
);
GlobalAsmOperandRef::Interpolate { string }
}
Err(ErrorHandled::Reported { .. }) => {
// An error has already been reported and
// compilation is guaranteed to fail if execution
// hits this path. So an empty string instead of
// a stringified constant value will suffice.
GlobalAsmOperandRef::Interpolate { string: "" }
}
Err(ErrorHandled::TooGeneric(_)) => {
span_bug!(*op_sp, "asm interpolate cannot be resolved; too generic")
}
}
}
rustc_hir::InlineAsmOperand::SymFn { expr } => {
let ty = cx.tcx().typeck(item_id.owner_id).expr_ty(expr);
let instance = match ty.kind() {
Expand Down
59 changes: 59 additions & 0 deletions compiler/rustc_codegen_ssa/src/common.rs
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@@ -1,7 +1,9 @@
#![allow(non_camel_case_types)]

use rustc_abi::{BackendRepr, Primitive, Scalar, Size};
use rustc_hir::LangItem;
use rustc_hir::attrs::PeImportNameType;
use rustc_middle::mir::interpret::{self, alloc_range};
use rustc_middle::ty::layout::TyAndLayout;
use rustc_middle::ty::{self, Instance, TyCtxt};
use rustc_middle::{bug, mir, span_bug};
Expand Down Expand Up @@ -170,6 +172,63 @@ pub fn asm_const_to_str<'tcx>(
}
}

pub fn asm_interpolate_to_str<'tcx>(

@Amanieu Amanieu Jun 3, 2026 •
edited by rustbot
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I'm not too familiar with the consteval code, but I wonder if some ugly edge cases could be triggered by passing in a const-transmute of something that isn't a slice (e.g. transmute a tuple of a dangling pointer + a random length to a &str). We shouldn't ICE in these cases, and instead return a proper error.

View changes since the review

@nbdd0121 nbdd0121 Jun 3, 2026

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consteval will check for validity invariant violations, so that should be the case, but safety invariant such as UTF-8 is not checked.

tcx: TyCtxt<'tcx>,
sp: Span,
const_value: mir::ConstValue,
ty_and_layout: TyAndLayout<'tcx>,
) -> &'tcx str {
let (alloc_id, range) = match const_value {
mir::ConstValue::Slice { alloc_id, meta } => {
(alloc_id, alloc_range(Size::ZERO, Size::from_bytes(meta)))
}
Comment on lines +182 to +184

@daxpedda daxpedda May 18, 2026 •
edited by rustbot
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I was unable to actually trigger this.
If this really can't happen we should remove it.

View changes since the review

mir::ConstValue::Indirect { alloc_id, offset } => {
let alloc = tcx.global_alloc(alloc_id).unwrap_memory().inner();

let BackendRepr::ScalarPair(
a @ Scalar::Initialized { value: Primitive::Pointer(_), .. },
b @ Scalar::Initialized { value: Primitive::Int(..), .. },
) = ty_and_layout.backend_repr
else {
span_bug!(
sp,
"expected slice ABI in Indirect for promoted asm interpolate, but got {:#?}",
ty_and_layout.backend_repr
)
};

let (a_size, b_size) = (a.size(&tcx), b.size(&tcx));
let b_offset = (offset + a_size).align_to(b.align(&tcx).abi);

let ptr = alloc.read_scalar(&tcx, alloc_range(offset, a_size), true);
let size = alloc.read_scalar(&tcx, alloc_range(b_offset, b_size), false);
let Ok(interpret::Scalar::Ptr(ptr, _)) = ptr else {
span_bug!(
sp,
"expected Ptr in ScalarPair for promoted asm interpolate, but got {ptr:#?}",
)
};
let Ok(interpret::Scalar::Int(size)) = size else {
span_bug!(
sp,
"expected Int in ScalarPair for promoted asm interpolate, but got {size:#?}",
)
};
Comment on lines +205 to +216

@daxpedda daxpedda May 18, 2026 •
edited by rustbot
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I'm not sure if this is overkill. Happy to just unwrap() + unreachable!() if it actually makes sense. I assume at least the interpret::Scalar variant could be behind an unreachable!() because we check the initial abi::Scalar above.

View changes since the review


(ptr.provenance.alloc_id(), alloc_range(Size::ZERO, Size::from_bytes(size)))
}
_ => span_bug!(
sp,
"expected Slice or Indirect for promoted asm interpolate, but got {:#?}",
const_value
),
};

let alloc = tcx.global_alloc(alloc_id).unwrap_memory().inner();
let bytes = alloc.get_bytes_strip_provenance(&tcx, range).unwrap();
unsafe { str::from_utf8_unchecked(bytes) }

@nbdd0121 nbdd0121 Jun 3, 2026 •
edited by rustbot
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This is unsound as bytes can be invalid UTF-8

View changes since the review

}

pub fn is_mingw_gnu_toolchain(target: &Target) -> bool {
target.os == Os::Windows && target.env == Env::Gnu && target.cfg_abi == CfgAbi::Unspecified
}
Expand Down
10 changes: 10 additions & 0 deletions compiler/rustc_codegen_ssa/src/mir/block.rs
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Expand Up @@ -1438,6 +1438,16 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
);
InlineAsmOperandRef::Const { string }
}
mir::InlineAsmOperand::Interpolate { ref value } => {
let const_value = self.eval_mir_constant(value);
let string = common::asm_interpolate_to_str(
bx.tcx(),
span,
const_value,
bx.layout_of(value.ty()),
);
InlineAsmOperandRef::Interpolate { string }
}
mir::InlineAsmOperand::SymFn { ref value } => {
let const_ = self.monomorphize(value.const_);
if let ty::FnDef(def_id, args) = *const_.ty().kind() {
Expand Down
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