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cmd/compile: delete the legacy compiler back end #16357

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randall77 opened this issue Jul 13, 2016 · 32 comments
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cmd/compile: delete the legacy compiler back end #16357

randall77 opened this issue Jul 13, 2016 · 32 comments
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@randall77
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When all the SSA backends are done, delete the legacy compiler.

This is basically a tracking bug for the work on all the SSA backends.

amd64 - done
arm - #15365
arm64 - #16009
ppc64 - #16010 #16175
@randall77 randall77 added this to the Go1.8 milestone Jul 13, 2016
@randall77 randall77 self-assigned this Jul 13, 2016
@randall77
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386 - #16358

@bradfitz
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mips64, @cherrymui ?

@cherrymui
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MIPS64- #16359

@randall77
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amd64p32 is now using the SSA backend.

https://go-review.googlesource.com/c/25586/

@randall77
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386 (including GO386=387) is now using the SSA backend.

@randall77
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ARM is done.

@bradfitz bradfitz mentioned this issue Aug 12, 2016
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@randall77
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MIPS64 is done.

All that is left is s390x and ppc64(be).

@dr2chase
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ppc64be lacks only a test machine.
Last time it was tested, it worked, or so I hear.

On Fri, Aug 26, 2016 at 4:51 PM, Keith Randall notifications@github.com
wrote:

MIPS64 is done.

All that is left is s390x and ppc64(be).

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@billotosyr
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working on s390x

@randall77
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arm64 is done.

@randall77
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s390x is done #16677
We now have the greenlight to start deleting the legacy compiler.
Any suggestions on how to do the equivalent of GOSSAHASH when there is no longer a legacy compiler are welcome.

@bradfitz
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@randall77, could GOSSAHASH remain but instead of using the old backend, mean to disable optimizations (like -N)?

@randall77
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That would work if you're hacking on an SSA pass that is disabled with -N. That covers some cases but not all.
I want something like "clone the cmd/compile/internal/ssa package. Develop a CL on one of them. Use GOSSAHASH to decide per-function whether to use the orignal or the modified version".
Maybe include cmd/compile/internal/gc/ssa.go and cmd/compile/internal/ARCH/ssa.go in that clone/swap process.

@josharian
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How about a top level flag (-hash=) and a support function (func hashmatch(name string) bool) that reports whether it matches. Then you can conditionally enable/disable any chunk of code you want, anywhere in the compiler.

@randall77
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An individual phase would be pretty easy to hack in by hand, yes.
You just have to duplicate the code in question and add a flag check. It gets daunting when your change is across 3 packages.

@dr2chase
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I've done Josh's method before, and I'm pretty happy with that method.
Some way of doing it wholesale old/new would be more than a little interesting.

@josharian
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Back to the exciting topic of deleting the old backend, Keith, it seems to me you should have the honor of doing the first big del, if you want it.

@josharian
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Another, much more complicated GOSSAHASH idea: Teach the linker to be able to combine two sources of object files. Using the known good compiler, compile everything and stash the object files. At link time, use GOSSAHASH to merge them. Wrap up behind a tool, maybe via -toolexec?

Sounds complicated, but maybe that's ok...or maybe it'll inspire a better idea in someone else.

@randall77
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I am licking my lips.

On Tue, Sep 13, 2016 at 1:52 PM, Josh Bleecher Snyder <
notifications@github.com> wrote:

Back to the exciting topic of deleting the old backend, Keith, it seems to
me you should have the honor of doing the first big del, if you want it.

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@dr2chase
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Given that we export all the phases as function pointers, this sort of old/new switchiness is perhaps not that magical. We might want to be more disciplined in our connections between gc/ssa.go and the ssa package.

@randall77
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I like Josh's idea. Kind of like a per-function toolstash. A hacky Go
program that takes two pkg directories and merges each .o/.a using hashes
of the function names to decide which one to take.

On Tue, Sep 13, 2016 at 2:00 PM, dr2chase notifications@github.com wrote:

Given that we export all the phases as function pointers, this sort of
old/new switchiness is perhaps not that magical. We might want to be more
disciplined in our connections between gc/ssa.go and the ssa package.

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@dr2chase
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Ah, I misunderstood. Is that going to be easy/possible to embed within make.bash or go test?

@josharian
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Ah, I misunderstood. Is that going to be easy/possible to embed within make.bash or go test?

You would presumably write a wrapper, like what buildall does for toolstash -cmp.

gopherbot pushed a commit that referenced this issue Sep 14, 2016
@randall77
cmd/compile: make ssa compilation unconditional
167e381 
Rip out the code that allows SSA to be used conditionally.

No longer exists:
 ssa=0 flag
 GOSSAHASH
 GOSSAPKG
 SSATEST

GOSSAFUNC now only controls the printing of the IR/html.

Still need to rip out all of the old backend.  It should no longer be
callable after this CL.

Update #16357

Change-Id: Ib30cc18fba6ca52232c41689ba610b0a94aa74f5
Reviewed-on: https://go-review.googlesource.com/29155
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>
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CL https://golang.org/cl/29168 mentions this issue.

gopherbot pushed a commit that referenced this issue Sep 15, 2016
@randall77
cmd/compile: delete lots of the legacy backend
e7cc9c4 
It's not everything, but it is a good start.

I tried to make the CL delete only.  goimports forced
a few exceptions to that rule.

Update #16357

Change-Id: I041925cb2fe68bb7ae1617af862b22c48da649c1
Reviewed-on: https://go-review.googlesource.com/29168
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>
Reviewed-by: Martin Möhrmann <martisch@uos.de>
@bradfitz
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More deletes for the record:

24965bc
ad7732a
f03855f
82703f8

gopherbot pushed a commit that referenced this issue Sep 15, 2016
@randall77
test: make SSA tests unconditional
f13701b 
Delete legacy backend tests, make SSA tests unconditional.

Next CL will remove _ssa from the file names.

Update #16357

Change-Id: I2a7f5dcbc69455f63b5e6e6b2725df26ab86c8dd
Reviewed-on: https://go-review.googlesource.com/29231
Run-TryBot: Keith Randall <khr@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
gopherbot pushed a commit that referenced this issue Sep 15, 2016
@randall77
test,cmd/compile: remove _ssa file suffix
b265d51 
Everything is SSA now.

Update #16357

Change-Id: I436dbe367b863ee81a3695a7d653ba4bfc5b0f6c
Reviewed-on: https://go-review.googlesource.com/29232
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
@bradfitz
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More:

f13701b
ae7e0ad
1f2930c
544010a
1bd91d4
9658de3

/cc @mdempsky

@mdempsky
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Should I start including and suggesting others to add "Updates #16357" to cleanup CLs related to this?

@randall77
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Yes, can't hurt.

On Fri, Sep 16, 2016 at 10:44 AM, Matthew Dempsky notifications@github.com
wrote:

Should I start including and suggesting others to add "Updates #16357
#16357" to cleanup CLs related to
this?

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#16357 (comment), or mute
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@mdempsky
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Roger roger.

@gopherbot
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CL https://golang.org/cl/29350 mentions this issue.

gopherbot pushed a commit that referenced this issue Sep 16, 2016
@mdempsky
cmd/compile: remove unused Label fields
9f447c2 
Updates #16357.

Change-Id: I37f04d83134b5e1e7f6ba44eb9a566758ef594d3
Reviewed-on: https://go-review.googlesource.com/29350
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
gopherbot pushed a commit that referenced this issue Sep 16, 2016
@mdempsky
cmd/compile: remove Arch.REGCTXT
08feadb 
Update #16357.

Change-Id: I507676212d7137a62c76de7bfa0ba8dbd68e840f
Reviewed-on: https://go-review.googlesource.com/29358
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Dave Cheney <dave@cheney.net>
gopherbot pushed a commit that referenced this issue Sep 17, 2016
@mdempsky
cmd/internal/obj: remove ACHECKNIL
246074d 
Updates #16357.

Change-Id: I35f938d675ca5c31f65c4419ee0732bbc593b5cb
Reviewed-on: https://go-review.googlesource.com/29368
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Dave Cheney <dave@cheney.net>
TryBot-Result: Gobot Gobot <gobot@golang.org>
@gopherbot
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CL https://golang.org/cl/29219 mentions this issue.

gopherbot pushed a commit that referenced this issue Sep 21, 2016
@mdempsky
cmd/compile: simplify obj.ProgInfo and extract from obj.Prog
e613470 
Updates #16357.

Change-Id: Ia837dd44bad76931baa9469e64371bc253d6694b
Reviewed-on: https://go-review.googlesource.com/29219
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
gopherbot pushed a commit that referenced this issue Sep 29, 2016
@ALTree @bradfitz
cmd/compile: delete unused (*Node) SetInt, SetBigInt, Bool
2b49d12 
Introduced in CL 9263 (prepare to unexport gc.Mp*) and CL 9267
(prepare Node.Val to be unexported), their only callers were in
the old backend and all got deleted in CL 29168 (cmd/compile:
delete lots of the legacy backend).

Update #16357

Change-Id: I0a5d76b98b418e8ec0984c033c3bc0ac3fc5f38a
Reviewed-on: https://go-review.googlesource.com/29997
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
gopherbot pushed a commit that referenced this issue Sep 30, 2016
@ALTree @bradfitz
cmd/compile: delete unused Convconst function
41fa42b 
Convconst is not used in the new backend, and all its callers
were deleted in CL 29168 (cmd/compile: delete lots of the legacy
backend). iconv was an helper function for Convconst.

Updates #16357

Change-Id: I65c7345586d7af81cdc2fb09c68f744ffb161a17
Reviewed-on: https://go-review.googlesource.com/30090
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
@randall77
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Declaring this done.

@rsc rsc changed the title cmd/compile: delete the legacy compiler cmd/compile: delete the legacy compiler back end Oct 17, 2016
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@bradfitz @mdempsky @josharian @dr2chase @randall77 @gopherbot @billotosyr @cherrymui