[PATCH 00/13] Go closures, libffi, and the static chain
Lynn A. Boger
laboger@linux.vnet.ibm.com
Wed Nov 5 21:34:00 GMT 2014
What about the libffi changes that are needed to make this work on other
platforms, like PowerPC?
On 10/10/2014 03:42 PM, Richard Henderson wrote:
> Pardon the wide distribution, the obvious hacks, and the failure
> to properly split up the largest of the libffi patches.
>
> The background here is my thread from last week[1], and Ian's reply[2],
> wherein he rightly points out that not needing to play games with
> mmap in order to implement closures for Go is a strong reason to
> continue using custom code within libgo.
>
> While that thread did have a go at implementing that custom code for
> aarch64, I still think that replicating libffi's calling convention
> knowledge for every interesting target is a mistake.
>
> So instead I thought about how I'd add some support for Go directly
> into libffi. After all, we've got some custom code in libffi for
> Java, why couldn't Go have the same treatment?
>
> The stickler, as far as I could see, is __go_set_context. I didn't
> like the idea of libffi needing a callback into libgo in order to
> accomplish the goal.
>
> But the comment immediately before __go_set_closure itself says
> that it would be better to use the static chain register. So I set
> about to see how easy that would be to accomplish. (And not for
> nothing such a change would make gccgo compiled programs faster
> by avoiding the library calls.)
>
> The following patch set enables this for x86_64, i386, and aarch64[3].
>
> The first two patches enable a static chain to be set by the front end
> on CALL_EXPRs, and to be used with indirect function calls. The third
> patch is a horrible hack to expose this feature to the C front end.
>
> The 4th patch changes gccgo to use the static chain. I don't bother
> with checking to see that the target has one. All targets currently
> supported by libgo have one, so I don't really see this as a stumbling
> block.
>
> The 5th patch changes libgo to use the static chain. I admit that I
> haven't tested this patch solo; I simply split it out of a larger patch
> for clarity.
>
> The 6th patch adds interfaces to libffi for Go; these interfaces are
> used within libgo in the 8th patch.
>
> Patches 7, 10, 11, 12, 13 are all enabling the new libffi interface on
> the aforementioned targets. There's lots of cleanup in here, and I
> owe the libffi list smaller reviewable changes. I ask that libffi
> ignore patches 10 and 12 for now and comment on the meat instead.
>
> Before I go too much farther down this road, I wanted to get some
> feedback. FWIW, a complete tree can be found at [4].
>
> Thanks,
>
>
> r~
>
>
> [1] https://gcc.gnu.org/ml/gcc-patches/2014-10/msg00098.html
> [2] https://gcc.gnu.org/ml/gcc-patches/2014-10/msg00102.html
> [3] Except that after rebasing the tree on yesterday's trunk,
> I discovered that i386 and aarch64 both have bootstrap
> problems on trunk. Ouch.
> [4] git://github.com/rth7680/gcc.git rth/go-closure
>
>
> Richard Henderson (13):
> Make TARGET_STATIC_CHAIN allow a function type
> Allow the front-end to create calls with a static chain
> HACK! Allow the static chain to be set from C
> Use the static chain as the closure parameter from Go
> libgo: Use the static chain for the closure
> libffi: Add entry points for interacting with Go
> libffi: Support go closures on x86_64
> libgo: Use the new libffi interfaces for Go
> libgo: Remove __go_get/set_closure
> libffi: Rewrite aarch64
> libffi: Support go closures on aarch64
> libffi: Rewrite i386 sysv
> libffi: Support go closures on i386
>
> gcc/c-family/c-common.c | 1 +
> gcc/c-family/c-common.h | 2 +-
> gcc/c/c-parser.c | 29 +
> gcc/calls.c | 14 +-
> gcc/config/i386/i386.c | 19 +-
> gcc/config/moxie/moxie.c | 5 +-
> gcc/config/xtensa/xtensa.c | 2 +-
> gcc/doc/tm.texi | 2 +-
> gcc/gimple-fold.c | 21 +
> gcc/gimplify.c | 17 +-
> gcc/go/go-gcc.cc | 44 +-
> gcc/go/gofrontend/backend.h | 7 +-
> gcc/go/gofrontend/expressions.cc | 21 +-
> gcc/go/gofrontend/gogo.cc | 29 +-
> gcc/go/gofrontend/gogo.h | 14 +
> gcc/go/gofrontend/runtime.def | 6 -
> gcc/target.def | 6 +-
> gcc/targhooks.c | 5 +-
> gcc/testsuite/gcc.dg/static-chain.c | 31 +
> gcc/tree-cfg.c | 22 +-
> libffi/include/ffi.h.in | 16 +
> libffi/src/aarch64/ffi.c | 1380 ++++++++++++++---------------------
> libffi/src/aarch64/ffitarget.h | 18 +-
> libffi/src/aarch64/internal.h | 43 ++
> libffi/src/aarch64/sysv.S | 557 +++++++-------
> libffi/src/x86/ffi.c | 1161 ++++++++++++-----------------
> libffi/src/x86/ffi64.c | 103 ++-
> libffi/src/x86/ffitarget.h | 112 ++-
> libffi/src/x86/internal.h | 48 ++
> libffi/src/x86/sysv.S | 1003 +++++++++++++++----------
> libffi/src/x86/unix64.S | 319 ++++----
> libgo/go/reflect/makefunc.go | 49 +-
> libgo/go/reflect/makefunc_386.S | 22 +-
> libgo/go/reflect/makefunc_amd64.S | 13 +-
> libgo/go/reflect/makefunc_ffi.go | 67 +-
> libgo/go/reflect/makefunc_ffi_c.c | 68 +-
> libgo/go/reflect/value.go | 3 +
> libgo/runtime/go-reflect-call.c | 10 +-
> libgo/runtime/malloc.goc | 8 -
> libgo/runtime/mgc0.c | 3 +-
> libgo/runtime/proc.c | 20 -
> libgo/runtime/runtime.h | 4 -
> libgo/runtime/time.goc | 3 +-
> 43 files changed, 2624 insertions(+), 2703 deletions(-)
> create mode 100644 gcc/testsuite/gcc.dg/static-chain.c
> create mode 100644 libffi/src/aarch64/internal.h
> create mode 100644 libffi/src/x86/internal.h
>
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