Andrew Trick f512bebf07 Add isReadOnlyConstantEvaluableCall to handle stdlib asserts ...

Fix isScopeAffectingInstructionDead to use this new API. A stdlib
assert, which has "program_termination" semantics, should not be
considered read-only.

isReadOnlyConstantEvaluableCall API:

/// Return true iff the \p applySite is constant-evaluable and read-only.
///
/// Functions annotated as "constant_evaluable" are assumed to be "side-effect
/// free", unless their signature and substitution map indicates otherwise. A
/// constant_evaluable function call is read only unless it:
///   (1) has generic parameters
///   (2) has inout parameters
///   (3) has indirect results
///
/// Read-only constant evaluable functions can do only the following and
/// nothing else:
///   (1) The call may read any memory location.
///   (2) The call may destroy owned parameters i.e., consume them.
///   (3) The call may write into memory locations newly created by the call.
///   (4) The call may use assertions, which traps at runtime on failure.
///   (5) The call may return a non-generic value.
///
/// Essentially, these are calls whose "effect" is visible only in their return
/// value or through the parameters that are destroyed. The return value
/// is also guaranteed to have value semantics as it is non-generic and
/// reference semantics is not constant evaluable.

2021-11-18 18:38:49 -08:00

9.7 KiB

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