[llvm-dev] -msave-args backend support for x86_64

[Joerg Sonnenberger via llvm-dev]

On Thu, Apr 27, 2017 at 12:00:37PM +0100, David Chisnall via llvm-dev wrote:
> This seems like a fragile and heavy hammer if your goal is simply to
> allow debuggers to find the arguments.  Wouldn’t it be simpler to mark
> the arguments as live for the entire call, so that the back end will
> either kepp them in registers or spill them, depending on register
> pressure, and update the DWARF frame info so that you can find them?

It is certainly missing frame info annotation, but the basic approach is
similar to what is already done for variadic functions on many
architectures with register-based argument handling. That leads me to
the question on whether this shouldn't be a generic code generation
flag.

Joerg