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Assembly Functions

This page is the language contract for assembly-backed functions. The assembly guide contains the complete syntax, operand tables, and target examples.

Complete Assembly Functions

[[asm]] gives a function a complete target-assembly body. The assembly is responsible for the declared calling ABI, including arguments, result, callee-saved state, stack discipline, and returning to the caller. The compiler does not emit a prologue or epilogue.

The body uses the colon/endfunc form. It cannot be external or abstract, and DQ parameter names and result are not substituted as operands.

Typed Inline Assembly Functions

[[inline, asm]] declares a typed template emitted at each direct call site. $parameter and $result name compiler-allocated operands. $$ emits a literal dollar sign.

Inline assembly functions are module-level direct-call operations. They do not have separately addressable function identities, cannot be methods or special functions, and cannot be converted to function references.

Operand Hints

One trailing attribute list may describe operands and effects:

  • immediate(parameter) requires a compile-time integer-like value;
  • memread(parameter), memwrite(parameter), and memreadwrite(parameter) describe typed memory effects;
  • clobber(resource) declares changed registers, flags, or all memory.

Every memory operand must be a typed pointer or a reference mode that permits the requested access. Every effect not represented by an output must be declared. Incorrect constraints can make optimized code invalid even if unoptimized code appears to work.

Source Processing

DQ comments and compiler conditionals are processed inside assembly bodies. Line-leading # is treated as a directive; after assembly text begins on a line, # remains target assembly syntax. In inline assembly, the trailing operand-hint list is metadata rather than an instruction.

Targets

Typed inline assembly is implemented for the documented x86-64, ARM/Thumb, AArch64, RV32, and RV64 target identifiers. Instruction syntax and available register classes come from the selected target and CPU features. Complete assembly functions may be accepted for other targets when the backend assembler supports their body, but ABI correctness remains the author's responsibility.