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[LangRef] inline asm: the instructions are treated opaquely #157080

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[LangRef] inline asm: the instructions are treated opaquely #157080

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[LangRef] inline asm: the template string is treated opaquely
RalfJung Sep 5, 2025
e5d04c8
explicitly mention self-modifying code
RalfJung Sep 15, 2025
077349a
only forbid correctness-critical analyses from inspecting the templat…
RalfJung Oct 3, 2025
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8 changes: 8 additions & 0 deletions llvm/docs/LangRef.rst
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Expand Up @@ -5229,6 +5229,14 @@ flag that indicates whether or not the inline asm expression has side effects,
and a flag indicating whether the function containing the asm needs to align its
stack conservatively.

The compiler may not assume that the actual code executed at runtime matches the
contents of the template string. Correctness-critical analyses must base their
results only on the list of operand constraints and the flags -- not the
contents of the template string. This ensures correct behavior if the assembly
code emitted by this expression is altered later, e.g. via self-modifying code,
as long as the code keeps upholding the requirements of the operand constraints
and the flags.

The template string supports argument substitution of the operands using "``$``"
followed by a number, to indicate substitution of the given register/memory
location, as specified by the constraint string. "``${NUM:MODIFIER}``" may also
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