In regalloc, we allocate some values to registers before loop entry,
so that they don't need to be loaded (from spill locations) during
the loop.
But it is pointless if we've already regalloc'd the loop body.
Whatever restores we needed for the body are already generated.
It's not clear if this code is ever useful. No tests fail if I just
remove it. But at least this change is worthwhile. It doesn't help,
and it actively inserts more restores than we really need (mostly
because the desired register list is approximate - I have seen cases
where the loads implicated here end up being dead because the restores
hit the wrong registers and the edge shuffle pass knows it needs
the restores in different registers).
While we are here, might as well have layoutRegallocOrder return
the standard layout order instead of recomputing it.
Change-Id: Ia624d5121de59b6123492603695de50b272b277f
Reviewed-on: https://go-review.googlesource.com/c/go/+/672735
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Keith Randall <khr@google.com>
Reviewed-by: David Chase <drchase@google.com>
We kind of have this mechanism already, just normalizing it and
using it in a bunch of places. Previously a bunch of places cached
slices only for the duration of a single function compilation. Now
we can reuse slices across a whole compiler run.
Use a sync.Pool of powers-of-two sizes. This lets us use not
too much memory, and avoid holding onto memory we're no longer
using when a GC happens.
There's a few different types we need, so generate the code for it.
Generics would be useful here, but we can't use generics in the
compiler because of bootstrapping.
Change-Id: I6cf37e7b7b2e802882aaa723a0b29770511ccd82
Reviewed-on: https://go-review.googlesource.com/c/go/+/444820
Run-TryBot: Keith Randall <khr@golang.org>
Reviewed-by: Heschi Kreinick <heschi@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>
steals idea from CL 312093
further investigation revealed additional duplicate
slots (equivalent, but not equal), so delete those too.
Rearranged Func.Names to be addresses of slots,
create canonical addresses so that split slots
(which use those addresses to refer to their parent,
and split slots can be further split)
will preserve "equivalent slots are equal".
Removes duplicates, improves metrics for "args at entry".
Change-Id: I5bbdcb50bd33655abcab3d27ad8cdce25499faaf
Reviewed-on: https://go-review.googlesource.com/c/go/+/312292
Trust: David Chase <drchase@google.com>
Run-TryBot: David Chase <drchase@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Cherry Mui <cherryyz@google.com>
Complete a long-standing TODO in the code.
Exit blocks are cold code, so we lay them out at the end of the function.
Blocks that are post-dominated by exit blocks are also ipso facto exit blocks.
Treat them as such.
Implement using a simple loop, because there are generally very few exit blocks.
In addition to improved instruction cache, this empirically yields
better register allocation.
Binary size impact:
file before after Δ %
cgo 4812872 4808776 -4096 -0.085%
fix 3370072 3365976 -4096 -0.122%
vet 8252280 8248184 -4096 -0.050%
total 115052984 115040696 -12288 -0.011%
This also appears to improve compiler performance
(-0.15% geomean time/op, -1.20% geomean user time/op),
but that could just be alignment effects.
Compiler benchmarking hasn't been super reliably recently,
and there's no particular reason to think this should
speed up the compiler that much.
Change-Id: I3d262c4f5cb80626a67a5c17285e2fa09f423c00
Reviewed-on: https://go-review.googlesource.com/c/go/+/227217
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>
This CL adds CFGs to ssa.html.
It execs dot to generate SVG,
which then gets inlined into the html.
Some standard naming and javascript hacks
enable integration with the rest of ssa.html.
Clicking on blocks highlights the relevant
part of the CFG, and vice versa.
Sample output and screenshots can be seen in #28177.
CFGs can be turned on with the suffix mask:
:* - dump CFG for every phase
:lower - just the lower phase
:lower-layout - lower through layout
:w,x-y - phases w and x through y
Calling dot after every pass is noticeably slow,
instead use the range of phases.
Dead blocks are not displayed on CFG.
User can zoom and pan individual CFG
when the automatic adjustment has failed.
Dot-related errors are reported
without bringing down the process.
Fixes#28177
Change-Id: Id52c42d86c4559ca737288aa10561b67a119c63d
Reviewed-on: https://go-review.googlesource.com/c/142517
Run-TryBot: Yury Smolsky <yury@smolsky.by>
Reviewed-by: David Chase <drchase@google.com>
While tinkering with different block orders for the preemptible
loop experiment, crashed the register allocator with a "bad"
one (these exist). Realized that one knob was controlling
two things (register allocation and branch patterns) and
decided that life would be simpler if the two orders were
independent.
Ran some experiments and determined that we have probably,
mostly, been optimizing for register allocation effects, not
branch effects. Bad block orders for register allocation are
somewhat costly.
This will also allow separate experimentation with perhaps-
better block orders for register allocation.
Change-Id: I6ecf2f24cca178b6f8acc0d3c4caaef043c11ed9
Reviewed-on: https://go-review.googlesource.com/47314
Run-TryBot: David Chase <drchase@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
Some minor scoping cleanups found by a very old version of grind.
Change-Id: I1d373817586445fc87e38305929097b652696fdd
Reviewed-on: https://go-review.googlesource.com/21064
Run-TryBot: Dave Cheney <dave@cheney.net>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
The SSA implementation logs for three purposes:
* debug logging
* fatal errors
* unimplemented features
Separating these three uses lets us attempt an SSA
implementation for all functions, not just
_ssa functions. This turns the entire standard
library into a compilation test, and makes it
easy to figure out things like
"how much coverage does SSA have now" and
"what should we do next to get more coverage?".
Functions called _ssa are still special.
They log profusely by default and
the output of the SSA implementation
is used. For all other functions,
logging is off, and the implementation
is built and discarded, due to lack of
support for the runtime.
While we're here, fix a few minor bugs and
add some extra Unimplementeds to allow
all.bash to pass.
As of now, SSA handles 20.79% of the functions
in the standard library (689 of 3314).
The top missing features are:
10.03% 2597 SSA unimplemented: zero for type error not implemented
7.79% 2016 SSA unimplemented: addr: bad op DOTPTR
7.33% 1898 SSA unimplemented: unhandled expr EQ
6.10% 1579 SSA unimplemented: unhandled expr OROR
4.91% 1271 SSA unimplemented: unhandled expr NE
4.49% 1163 SSA unimplemented: unhandled expr LROT
4.00% 1036 SSA unimplemented: unhandled expr LEN
3.56% 923 SSA unimplemented: unhandled stmt CALLFUNC
2.37% 615 SSA unimplemented: zero for type []byte not implemented
1.90% 492 SSA unimplemented: unhandled stmt CALLMETH
1.74% 450 SSA unimplemented: unhandled expr CALLINTER
1.74% 450 SSA unimplemented: unhandled expr DOT
1.71% 444 SSA unimplemented: unhandled expr ANDAND
1.65% 426 SSA unimplemented: unhandled expr CLOSUREVAR
1.54% 400 SSA unimplemented: unhandled expr CALLMETH
1.51% 390 SSA unimplemented: unhandled stmt SWITCH
1.47% 380 SSA unimplemented: unhandled expr CONV
1.33% 345 SSA unimplemented: addr: bad op *
1.30% 336 SSA unimplemented: unhandled OLITERAL 6
Change-Id: I4ca07951e276714dc13c31de28640aead17a1be7
Reviewed-on: https://go-review.googlesource.com/11160
Reviewed-by: Keith Randall <khr@golang.org>
Semi-regular merge of tip to dev.ssa.
Complicated a bit by the move of cmd/internal/* to cmd/compile/internal/*.
Change-Id: I1c66d3c29bb95cce4a53c5a3476373aa5245303d
