Support using const pointers in asm const operand
#138618
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This is used for string interpolation currently, so rename it as so. The name `Const` will be used to denote a general CTFE constant that can either be integer or pointer.
This is intended for supporting passing arbitrary CTFE const into inline assembly.
`global_asm!` themselves don't need symbol names; they currently only have a symbol name during mono collecion to identify them to partitioning algorithm. However it will have shims generated under it which will need unique symbol names. The name themselves ultimately doesn't matter, so they're generated like other shim instances.
This is currently a no-op, but will be useful when const in `global_asm!` can be pointers.
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tmiasko
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Apr 10, 2025
| @@ -25,9 +26,12 @@ pub enum InlineAsmOperandRef<'tcx, B: BackendTypes + ?Sized> { | |||
| in_value: OperandRef<'tcx, B::Value>, | |||
| out_place: Option<PlaceRef<'tcx, B::Value>>, | |||
| }, | |||
| Const { | |||
| Interpolate { | |||
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Please add more doc comment explaining the significance of the difference between Interpolate and Const for backends. It begs the question for why we ever turn const operands into strings, for example.
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| value: mir::interpret::Pointer, | ||
| /// Instance that instantiates this const operand. | ||
| instance: Instance<'tcx>, |
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Why do we need both a value and an instance?
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Implements #128464
This adds support of const pointers for asm
constin addition to plain integers.The inline
asm!support is implemented usingiconstraint, and theglobal_asm!andnaked_asm!support is implemented by insertingsymbol + offsetand makesymbolcompiler-used. For unnamed consts, it will create additional internal & hidden symbols so that they can be referenced by global_asm.The feature is also implemented for GCC backend but it's untested.