charon_lib

Module transform

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  • Check that all supplied generic types match the corresponding generic parameters.
  • We cannot filter trait impls by name before translating them, because we need to know the trait/type pair that is being implemented. We therefore filter them in a post-processing pass.
  • Desugar array/slice index operations to function calls.
  • panic!() expands to:
  • When the function’s return type is unit, the generated MIR doesn’t set the return value to (). This can be a concern: in the case of AENEAS, it means the return variable contains ⊥ upon returning. For this reason, when the function has return type unit, we insert an extra assignment just before returning.
  • Move clauses on associated types to be parent clauses. The distinction is not semantically meaningful. We should ideally to this directly when translating but this is currently difficult; instead we do this as a post-processing pass.
  • Micro-pass: merge single-origin gotos into their parent to reduce CFG graph size.
  • Desugar some unary/binary operations and the array repeats to function calls. For instance, we desugar ArrayToSlice from an unop to a function call. This allows a more uniform treatment later on. TODO: actually transform all the unops and binops to function calls?
  • In the MIR AST, it seems assert are introduced to check preconditions (for the binops for example). The assert! introduced by the user introduce if ... then { panic!(...) } else { ...}. This pass introduces assert instead in order to make the code shorter.
  • Micro-pass: reconstruct piecewise box allocations using malloc and ShallowInitBox.
  • Take all the comments found in the original body and assign them to statements.
  • Micro-pass: remove the overflow checks for arithmetic operations we couldn’t remove in
  • The MIR code often contains variables with type Never, and we want to get rid of those. We proceed in two steps. First, we remove the instructions drop(v) where v has type Never (it can happen - this module does the filtering). Then, we filter the unused variables ([crate::remove_unused_locals]).
  • Micro-pass: remove the dynamic checks for array/slice bounds, overflow, and division by zero.
  • Remove the useless no-ops.
  • The MIR code often contains variables with type Never, and we want to get rid of those. We proceed in two steps. First, we remove the instructions drop(v) where v has type Never (it can happen - this module does the filtering). Then, we filter the unused variables ([crate::remove_unused_locals]).
  • Remove the locals (which are not used for the input arguments) which are never used in the function bodies. This is useful to remove the locals with type Never. We actually check that there are no such local variables remaining afterwards.
  • The MIR constant expressions lead to a lot of duplication: there are for instance constant ADTs which duplicate the “regular” aggregated ADTs in the operands, constant references, etc. This reduces the number of cases to handle and eases the function translation in Aeneas.
  • ULLBC to LLBC
  • Update the block indices to make sure they are consecutive
  • Micro-pass: the first local variable of closures is (a borrow to) the

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