tree e1ae9446394d9b00294e63d9603237738b732b6e
parent 4773c6fafff3381a238f214c68130c7bfe02400d
author Gabe Black <gabeblack@google.com> 1588149160 -0700
committer Gabe Black <gabeblack@google.com> 1588236453 +0000

sim: Add an option to suppress the return value in invokeSimcall.

Sometimes when using the GuestABI mechanism, gem5 wants to know that a
function was called and with what arguments to do its own processing,
but doesn't want to return its own value since it will still let the
simulated system execute its own function. There are also situations
where gem5 wants to return a value, but not through the normal
mechanism. That happens when, for instance, a gem5 op is triggered by a
memory access, and that access is what should return the value, not a
particular fixed register.

This option is a template parameter rather than a function argument so
that if it's not going to be used, no "Return" type needs to be defined
since it's not present at all in the chain of functions invokeSimcall
expands to.

This will also make it easier to reuse generic ABIs in those situations
without having to make custom wrappers.

Change-Id: I969e78495c8f4e73f4de1a3dfb4d74c9b30f5af5
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/28288
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Maintainer: Gabe Black <gabeblack@google.com>
Tested-by: kokoro <noreply+kokoro@google.com>