Switch from recursing into non-canonical instruction fields to
separately canonicalizing those fields. This means we now form canonical
`InstBlockId`s, `TypeBlockId`s, `IntId`s, `FloatId`s, and `BindNameId`s
at least in the cases when they're referenced by a constant instruction.
This reduces the overall runtime for @chandlerc's 10MLoC example by
27.5% on my machine.
Use a level comparison during substitution to determine whether we're
substituting a particular binding. Evaluate symbolic bindings with the
same name and the same level to the same symbolic constant, for example
across redeclarations of a generic function.
Add a general substitution mechanism to support substituting symbolic
bindings with their values throughout symbolic constants and, more
specifically, types. This is done by decomposing the constant
instruction into its operands, substituting into the operands, and then
rebuilding the constant value by invoking the constant evaluator.
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Co-authored-by: Jon Ross-Perkins <jperkins@google.com>
Co-authored-by: Carbon Infra Bot <carbon-external-infra@google.com>
Richard Smith
