• Austin Clements's avatar
    cmd/compile, cmd/link: separate stable and internal ABIs · 685aca45
    Austin Clements authored
    This implements compiler and linker support for separating the
    function calling ABI into two ABIs: a stable and an internal ABI. At
    the moment, the two ABIs are identical, but we'll be able to evolve
    the internal ABI without breaking existing assembly code that depends
    on the stable ABI for calling to and from Go.
    
    The Go compiler generates internal ABI symbols for all Go functions.
    It uses the symabis information produced by the assembler to create
    ABI wrappers whenever it encounters a body-less Go function that's
    defined in assembly or a Go function that's referenced from assembly.
    
    Since the two ABIs are currently identical, for the moment this is
    implemented using "ABI alias" symbols, which are just forwarding
    references to the native ABI symbol for a function. This way there's
    no actual code involved in the ABI wrapper, which is good because
    we're not deriving any benefit from it right now. Once the ABIs
    diverge, we can eliminate ABI aliases.
    
    The linker represents these different ABIs internally as different
    versions of the same symbol. This way, the linker keeps us honest,
    since every symbol definition and reference also specifies its
    version. The linker is responsible for resolving ABI aliases.
    
    Fixes #27539.
    
    Change-Id: I197c52ec9f8fc435db8f7a4259029b20f6d65e95
    Reviewed-on: https://go-review.googlesource.com/c/147160
    Run-TryBot: Austin Clements <austin@google.com>
    TryBot-Result: Gobot Gobot <gobot@golang.org>
    Reviewed-by: 's avatarDavid Chase <drchase@google.com>
    685aca45
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