• Cherry Zhang's avatar
    cmd/compile: set/unset base register for better assembly print · f20944de
    Cherry Zhang authored
    For address of an auto or arg, on all non-x86 architectures
    the assembler backend encodes the actual SP offset in the
    instruction but leaves the offset in Prog unchanged. When the
    assembly is printed in compile -S, it shows an offset
    relative to pseudo FP/SP with an actual hardware SP base
    register (e.g. R13 on ARM). This is confusing. Unset the
    base register if it is indeed SP, so the assembly output is
    consistent. If the base register isn't SP, it should be an
    error and the error output contains the actual base register.
    
    For address loading instructions, the base register isn't set
    in the compiler on non-x86 architectures. Set it. Normally it
    is SP and will be unset in the change mentioned above for
    printing. If it is not, it will be an error and the error
    output contains the actual base register.
    
    No change in generated binary, only printed assembly. Passes
    "go build -a -toolexec 'toolstash -cmp' std cmd" on all
    architectures.
    
    Fixes #21064.
    
    Change-Id: Ifafe8d5f9b437efbe824b63b3cbc2f5f6cdc1fd5
    Reviewed-on: https://go-review.googlesource.com/49432
    Run-TryBot: Cherry Zhang <cherryyz@google.com>
    TryBot-Result: Gobot Gobot <gobot@golang.org>
    Reviewed-by: 's avatarDavid Chase <drchase@google.com>
    f20944de
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