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ade0811dc8
Prior to this change, the shortcircuit pass could only
handle blocks containing only a single phi control value,
possibly wrapped in some OpNot and OpCopy values.
This change partially lifts this limitation.
It handles some cases in which the block contains other phi values.
This appears to happen most commonly in cases in which
the conditionals being checked involve the memory state,
in which case there is a phi memory value in the block.
The general idea here is to use the information we have about
the CFG to (1) move the other phi values into other blocks
and/or (2) rewrite uses of the other phi values in other blocks.
For example, consider this CFG:
p q
\ /
b
/ \
t u
And consider a phi value v in block b.
We'll write v = Phi(p: x, q: y) to say that v has value x corresponding
to inbound block p, and value y for block q.
We will rewrite this CFG to:
p q
| /
| b
|/ \
t u
What should we do with v?
Any uses of v in u can be replaced with y. Why?
If we are in block u, we came from b, and before that from q.
If prior to b we came from p, then we would have gone to t, not u.
Since we came from q, we know that v took the value y.
Uses of v in t are a bit more complicated.
It is going to end up being a phi value: Phi(p: ?, b: ?).
Suppose, after the rewrite, we came from block p.
Then, before the rewrite, we would have gone to b,
where v would have the value x.
So we have Phi(p: x, b: ?).
Suppose, after the rewrite, we came from block b.
Then we must have come from block q.
If we come from block q, v has value y.
So we have Phi(p: x, b: y).
Uses of v in t can thus be replaced with a new phi value,
with the same values as v, but with altered predecessors.
Similar reasoning can be employed to rewrite or replace
other uses of v elsewhere in the CFG, so that v itself can be eliminated,
and the CFG rewrite can proceed.
This change sets up the infrastructure for such optimizations
and adds a few cheap ones. All optimizations in this change depend
only on the shape of the CFG; future changes may also depend on where
v's uses are. That analysis is more powerful but more expensive,
and should be done incrementally.
The use of closures here is perhaps a bit unusual,
but during development it proved critical to having readable code.
We must decide early on whether we can safely do the CFG modifications,
and then later fix up the phis if so.
Safely storing state and decisions across these two phases is hard to do readably.
Closures solve the problem neatly.
I manually instrumented the code paths in shortcircuitPhiPlan.
During make.bash there are nearly 6000 invocations.
The least-visited code path gets run 85 times,
so all the code in this CL is reasonably well-exercised.
Here is a concrete example of code improved by this change:
func f(e interface{}) int {
if x, ok := e.(int); ok {
return x
}
return 0
}
Omitting PCDATA, FUNCDATA, and the like, it used to compile to:
"".f STEXT nosplit size=50 args=0x18 locals=0x0
0x0000 00000 (x.go:4) LEAQ type.int(SB), AX
0x0007 00007 (x.go:4) MOVQ "".e+8(SP), CX
0x000c 00012 (x.go:4) CMPQ AX, CX
0x000f 00015 (x.go:4) JNE 43
0x0011 00017 (x.go:4) MOVQ "".e+16(SP), AX
0x0016 00022 (x.go:4) MOVQ (AX), AX
0x0019 00025 (x.go:4) JNE 33
0x001b 00027 (x.go:5) MOVQ AX, "".~r1+24(SP)
0x0020 00032 (x.go:5) RET
0x0021 00033 (x.go:7) MOVQ $0, "".~r1+24(SP)
0x002a 00042 (x.go:7) RET
0x002b 00043 (x.go:7) MOVL $0, AX
0x0030 00048 (x.go:4) JMP 25
Afterwards, it compiles to:
"".f STEXT nosplit size=41 args=0x18 locals=0x0
0x0000 00000 (x.go:4) LEAQ type.int(SB), AX
0x0007 00007 (x.go:4) MOVQ "".e+8(SP), CX
0x000c 00012 (x.go:4) CMPQ AX, CX
0x000f 00015 (x.go:4) JNE 31
0x0011 00017 (x.go:4) MOVQ "".e+16(SP), AX
0x0016 00022 (x.go:4) MOVQ (AX), AX
0x0019 00025 (x.go:5) MOVQ AX, "".~r1+24(SP)
0x001e 00030 (x.go:5) RET
0x001f 00031 (x.go:7) MOVQ $0, "".~r1+24(SP)
0x0028 00040 (x.go:7) RET
Note that there is now only a single JNE and a single RET $0 path.
Updates #37608
Has a minor good effect on compilation speed and memory use.
Provides widespread improvements to generated code.
The rare, minor regressions I have investigated are due to
register allocation fluctuations.
file before after Δ %
addr2line 4376080 4371984 -4096 -0.094%
api 5945400 5933112 -12288 -0.207%
asm 5034312 5030216 -4096 -0.081%
buildid 2844952 2840856 -4096 -0.144%
cgo 4812872 4804680 -8192 -0.170%
compile 19622064 19610368 -11696 -0.060%
cover 5236648 5232552 -4096 -0.078%
dist 3658312 3654216 -4096 -0.112%
doc 4653512 4649416 -4096 -0.088%
fix 3370072 3365976 -4096 -0.122%
link 6671864 6667768 -4096 -0.061%
pprof 14781652 14761172 -20480 -0.139%
trace 11639684 11627396 -12288 -0.106%
vet 8252280 8231800 -20480 -0.248%
total 115052984 114934792 -118192 -0.103%
file before after Δ %
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internal/bytealg.s 1730 1737 +7 +0.405%
cmd/vendor/golang.org/x/mod/semver.s 7332 7283 -49 -0.668%
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math/cmplx.s 6596 6575 -21 -0.318%
runtime.s 480566 480053 -513 -0.107%
sync.s 16408 16385 -23 -0.140%
math/rand.s 10447 10406 -41 -0.392%
internal/reflectlite.s 28408 28366 -42 -0.148%
errors.s 2736 2701 -35 -1.279%
sort.s 17031 17036 +5 +0.029%
io.s 16993 16964 -29 -0.171%
container/heap.s 2006 1997 -9 -0.449%
text/tabwriter.s 9570 9552 -18 -0.188%
bytes.s 31823 31594 -229 -0.720%
strconv.s 52760 52717 -43 -0.082%
vendor/golang.org/x/text/transform.s 16713 16706 -7 -0.042%
strings.s 42590 42563 -27 -0.063%
bufio.s 22883 22785 -98 -0.428%
encoding/base32.s 9586 9531 -55 -0.574%
syscall.s 82237 82243 +6 +0.007%
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regexp/syntax.s 82827 82769 -58 -0.070%
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regexp.s 64114 64049 -65 -0.101%
os.s 51751 51524 -227 -0.439%
reflect.s 168240 168049 -191 -0.114%
cmd/go/internal/lockedfile/internal/filelock.s 2317 2290 -27 -1.165%
path/filepath.s 17831 17766 -65 -0.365%
io/ioutil.s 6994 6990 -4 -0.057%
encoding/binary.s 30791 30726 -65 -0.211%
cmd/vendor/golang.org/x/sys/unix.s 78055 78033 -22 -0.028%
encoding/pem.s 9280 9247 -33 -0.356%
crypto/cipher.s 20376 20374 -2 -0.010%
os/exec.s 29229 29140 -89 -0.304%
internal/goroot.s 4588 4579 -9 -0.196%
cmd/internal/browser.s 2246 2240 -6 -0.267%
cmd/vendor/golang.org/x/crypto/ssh/terminal.s 27183 27149 -34 -0.125%
fmt.s 76625 76484 -141 -0.184%
encoding/hex.s 6154 6152 -2 -0.032%
compress/lzw.s 7063 7059 -4 -0.057%
database/sql/driver.s 18875 18862 -13 -0.069%
debug/plan9obj.s 8268 8266 -2 -0.024%
net/url.s 29724 29719 -5 -0.017%
encoding/csv.s 12872 12856 -16 -0.124%
debug/gosym.s 25303 25268 -35 -0.138%
compress/flate.s 50952 51019 +67 +0.131%
compress/zlib.s 7277 7266 -11 -0.151%
archive/zip.s 42155 42111 -44 -0.104%
debug/dwarf.s 107632 107541 -91 -0.085%
database/sql.s 98373 98028 -345 -0.351%
os/user.s 14722 14708 -14 -0.095%
encoding/json.s 105836 105711 -125 -0.118%
debug/macho.s 32598 32560 -38 -0.117%
encoding/gob.s 136478 135755 -723 -0.530%
debug/pe.s 31160 30869 -291 -0.934%
debug/elf.s 63495 63302 -193 -0.304%
vendor/golang.org/x/text/unicode/bidi.s 27220 27217 -3 -0.011%
vendor/golang.org/x/text/secure/bidirule.s 3363 3352 -11 -0.327%
go/token.s 12036 12035 -1 -0.008%
flag.s 22277 22256 -21 -0.094%
mime.s 39696 39509 -187 -0.471%
go/scanner.s 19033 19020 -13 -0.068%
archive/tar.s 70936 70581 -355 -0.500%
internal/xcoff.s 22823 22820 -3 -0.013%
text/scanner.s 11631 11629 -2 -0.017%
encoding/xml.s 110534 110408 -126 -0.114%
math/big.s 183636 183545 -91 -0.050%
image/gif.s 27376 27343 -33 -0.121%
crypto/dsa.s 6029 5969 -60 -0.995%
image/png.s 42947 42939 -8 -0.019%
crypto/rand.s 6866 6854 -12 -0.175%
vendor/golang.org/x/text/unicode/norm.s 66394 66354 -40 -0.060%
runtime/trace.s 2603 2521 -82 -3.150%
crypto/ed25519.s 6321 6300 -21 -0.332%
text/template/parse.s 93910 93844 -66 -0.070%
crypto/rsa.s 31460 31369 -91 -0.289%
encoding/asn1.s 57021 57023 +2 +0.004%
crypto/elliptic.s 51382 51363 -19 -0.037%
crypto/x509/pkix.s 10386 10342 -44 -0.424%
vendor/golang.org/x/net/idna.s 24482 24466 -16 -0.065%
vendor/golang.org/x/crypto/cryptobyte.s 33479 33280 -199 -0.594%
crypto/ecdsa.s 11936 11883 -53 -0.444%
go/constant.s 43670 42663 -1007 -2.306%
go/ast.s 80383 80191 -192 -0.239%
testing.s 68069 68057 -12 -0.018%
runtime/pprof.s 59613 59603 -10 -0.017%
testing/iotest.s 4895 4891 -4 -0.082%
internal/trace.s 78136 78089 -47 -0.060%
cmd/internal/goobj2.s 13158 13154 -4 -0.030%
cmd/internal/src.s 17661 17657 -4 -0.023%
go/parser.s 79046 78880 -166 -0.210%
cmd/internal/objabi.s 16367 16343 -24 -0.147%
text/template.s 94899 94486 -413 -0.435%
go/printer.s 77267 76992 -275 -0.356%
cmd/internal/goobj.s 25988 25947 -41 -0.158%
runtime/pprof/internal/profile.s 102066 101933 -133 -0.130%
go/format.s 5419 5371 -48 -0.886%
cmd/vendor/golang.org/x/arch/ppc64/ppc64asm.s 37181 37149 -32 -0.086%
go/doc.s 74533 74132 -401 -0.538%
html/template.s 88743 88389 -354 -0.399%
cmd/asm/internal/lex.s 24881 24872 -9 -0.036%
cmd/internal/buildid.s 18263 18256 -7 -0.038%
cmd/vendor/golang.org/x/arch/x86/x86asm.s 80036 79980 -56 -0.070%
go/build.s 68905 68737 -168 -0.244%
cmd/cover.s 46070 45950 -120 -0.260%
cmd/internal/obj.s 117001 116991 -10 -0.009%
cmd/doc.s 62700 62419 -281 -0.448%
cmd/internal/obj/arm.s 66745 66687 -58 -0.087%
cmd/compile/internal/syntax.s 145406 145062 -344 -0.237%
cmd/internal/obj/wasm.s 44049 44027 -22 -0.050%
net.s 291835 291020 -815 -0.279%
cmd/dist.s 209020 208807 -213 -0.102%
cmd/cgo.s 241564 241102 -462 -0.191%
vendor/golang.org/x/net/http/httpproxy.s 9407 9399 -8 -0.085%
log/syslog.s 7921 7909 -12 -0.151%
go/types.s 319325 317513 -1812 -0.567%
vendor/golang.org/x/net/http/httpguts.s 3834 3825 -9 -0.235%
mime/multipart.s 21414 21343 -71 -0.332%
cmd/internal/obj/ppc64.s 119949 119938 -11 -0.009%
cmd/compile/internal/logopt.s 10158 10118 -40 -0.394%
vendor/golang.org/x/net/nettest.s 28012 27991 -21 -0.075%
go/internal/srcimporter.s 6405 6380 -25 -0.390%
go/internal/gcimporter.s 34525 34493 -32 -0.093%
net/mail.s 23937 23720 -217 -0.907%
go/internal/gccgoimporter.s 56095 56038 -57 -0.102%
cmd/compile/internal/types.s 47247 47207 -40 -0.085%
cmd/api.s 39582 39558 -24 -0.061%
cmd/go/internal/base.s 12572 12551 -21 -0.167%
cmd/vendor/golang.org/x/xerrors.s 17846 17814 -32 -0.179%
cmd/vendor/golang.org/x/mod/sumdb/note.s 18142 18070 -72 -0.397%
cmd/go/internal/search.s 19994 19876 -118 -0.590%
cmd/go/internal/imports.s 16457 16428 -29 -0.176%
cmd/vendor/golang.org/x/mod/module.s 17838 17759 -79 -0.443%
cmd/go/internal/cache.s 30551 30514 -37 -0.121%
cmd/vendor/golang.org/x/mod/sumdb/tlog.s 36356 36321 -35 -0.096%
cmd/internal/test2json.s 9452 9408 -44 -0.466%
cmd/go/internal/mvs.s 25136 25092 -44 -0.175%
cmd/go/internal/txtar.s 3488 3461 -27 -0.774%
cmd/vendor/golang.org/x/mod/zip.s 18811 18800 -11 -0.058%
cmd/go/internal/version.s 11213 11171 -42 -0.375%
cmd/link/internal/benchmark.s 4941 4949 +8 +0.162%
cmd/internal/obj/s390x.s 126865 126849 -16 -0.013%
cmd/gofmt.s 30684 30596 -88 -0.287%
cmd/fix.s 87450 86906 -544 -0.622%
cmd/internal/obj/x86.s 88578 88556 -22 -0.025%
cmd/vendor/golang.org/x/mod/modfile.s 72450 72363 -87 -0.120%
cmd/oldlink/internal/loader.s 16743 16741 -2 -0.012%
cmd/pack.s 14863 14861 -2 -0.013%
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cmd/oldlink/internal/loadmacho.s 29309 29317 +8 +0.027%
cmd/oldlink/internal/loadelf.s 35013 35021 +8 +0.023%
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cmd/link/internal/loader.s 94765 94564 -201 -0.212%
cmd/link/internal/loadelf.s 35663 35667 +4 +0.011%
cmd/link/internal/loadmacho.s 29501 29509 +8 +0.027%
cmd/vendor/golang.org/x/tools/go/analysis.s 4983 4976 -7 -0.140%
cmd/vendor/golang.org/x/tools/go/analysis/internal/analysisflags.s 16771 16709 -62 -0.370%
cmd/vendor/golang.org/x/tools/go/types/objectpath.s 18481 18456 -25 -0.135%
cmd/vendor/golang.org/x/tools/go/analysis/passes/internal/analysisutil.s 2100 2085 -15 -0.714%
cmd/vendor/github.com/google/pprof/profile.s 150141 149620 -521 -0.347%
cmd/vendor/github.com/google/pprof/internal/measurement.s 10420 10404 -16 -0.154%
cmd/vendor/golang.org/x/tools/go/analysis/passes/asmdecl.s 36814 36755 -59 -0.160%
cmd/vendor/golang.org/x/tools/go/analysis/passes/bools.s 6688 6673 -15 -0.224%
cmd/vendor/golang.org/x/tools/go/analysis/passes/cgocall.s 9856 9784 -72 -0.731%
cmd/vendor/golang.org/x/tools/go/analysis/passes/composite.s 3011 2979 -32 -1.063%
cmd/vendor/golang.org/x/tools/go/analysis/passes/copylock.s 9737 9682 -55 -0.565%
cmd/vendor/golang.org/x/tools/go/cfg.s 30738 30725 -13 -0.042%
cmd/vendor/github.com/ianlancetaylor/demangle.s 175195 174513 -682 -0.389%
cmd/vendor/golang.org/x/tools/go/analysis/passes/httpresponse.s 3625 3520 -105 -2.897%
cmd/vendor/golang.org/x/tools/go/analysis/passes/loopclosure.s 2987 2971 -16 -0.536%
cmd/vendor/golang.org/x/tools/go/analysis/passes/shift.s 4372 4340 -32 -0.732%
cmd/vendor/golang.org/x/tools/go/analysis/passes/stdmethods.s 8634 8611 -23 -0.266%
cmd/vendor/golang.org/x/tools/go/analysis/passes/tests.s 6189 6164 -25 -0.404%
cmd/vendor/golang.org/x/tools/go/analysis/passes/structtag.s 8089 8073 -16 -0.198%
cmd/vendor/golang.org/x/tools/go/analysis/passes/unsafeptr.s 2208 2177 -31 -1.404%
cmd/vendor/golang.org/x/tools/go/analysis/passes/unreachable.s 8050 8047 -3 -0.037%
cmd/vendor/golang.org/x/tools/go/analysis/passes/unusedresult.s 3665 3629 -36 -0.982%
cmd/vendor/golang.org/x/tools/go/ast/astutil.s 65773 65680 -93 -0.141%
cmd/vendor/golang.org/x/tools/go/analysis/unitchecker.s 13328 13286 -42 -0.315%
cmd/vendor/golang.org/x/tools/go/types/typeutil.s 12263 12162 -101 -0.824%
cmd/vendor/golang.org/x/tools/go/analysis/passes/errorsas.s 1459 1421 -38 -2.605%
cmd/vendor/golang.org/x/tools/go/analysis/passes/ctrlflow.s 5208 5191 -17 -0.326%
cmd/vendor/golang.org/x/tools/go/analysis/passes/unmarshal.s 1801 1782 -19 -1.055%
cmd/vendor/golang.org/x/tools/go/analysis/passes/lostcancel.s 9569 9528 -41 -0.428%
cmd/go/internal/work.s 304928 304756 -172 -0.056%
crypto/x509.s 147340 147139 -201 -0.136%
cmd/vendor/golang.org/x/tools/go/analysis/passes/printf.s 34287 34019 -268 -0.782%
crypto/tls.s 311603 310644 -959 -0.308%
cmd/oldlink/internal/ld.s 533115 532651 -464 -0.087%
cmd/oldlink/internal/wasm.s 16484 16458 -26 -0.158%
cmd/oldlink/internal/x86.s 18832 18830 -2 -0.011%
cmd/link/internal/ld.s 548200 547626 -574 -0.105%
cmd/link/internal/wasm.s 16760 16734 -26 -0.155%
cmd/link/internal/arm64.s 20850 20840 -10 -0.048%
cmd/link/internal/x86.s 17437 17435 -2 -0.011%
net/http.s 556647 555519 -1128 -0.203%
net/http/cookiejar.s 15849 15833 -16 -0.101%
expvar.s 9521 9508 -13 -0.137%
net/http/httptest.s 16471 16452 -19 -0.115%
cmd/vendor/github.com/google/pprof/internal/plugin.s 4266 4264 -2 -0.047%
net/http/cgi.s 23448 23428 -20 -0.085%
cmd/go/internal/web.s 16472 16428 -44 -0.267%
net/http/httputil.s 39672 39670 -2 -0.005%
net/rpc.s 33989 33965 -24 -0.071%
net/http/fcgi.s 19167 19162 -5 -0.026%
cmd/vendor/github.com/google/pprof/internal/symbolz.s 5861 5857 -4 -0.068%
cmd/vendor/github.com/google/pprof/internal/binutils.s 35842 35823 -19 -0.053%
cmd/vendor/github.com/google/pprof/internal/symbolizer.s 11449 11404 -45 -0.393%
cmd/go/internal/get.s 62726 62582 -144 -0.230%
cmd/vendor/github.com/google/pprof/internal/report.s 80032 80022 -10 -0.012%
cmd/go/internal/modfetch/codehost.s 89005 88871 -134 -0.151%
cmd/trace.s 116607 116496 -111 -0.095%
cmd/vendor/github.com/google/pprof/internal/driver.s 143234 143207 -27 -0.019%
cmd/vendor/github.com/google/pprof/driver.s 9000 8998 -2 -0.022%
cmd/go/internal/modfetch.s 126300 125726 -574 -0.454%
cmd/pprof.s 12317 12312 -5 -0.041%
cmd/go/internal/modconv.s 17878 17861 -17 -0.095%
cmd/go/internal/modload.s 150261 149763 -498 -0.331%
cmd/go/internal/clean.s 11122 11091 -31 -0.279%
cmd/go/internal/help.s 6523 6521 -2 -0.031%
cmd/go/internal/generate.s 11627 11614 -13 -0.112%
cmd/go/internal/envcmd.s 22034 21986 -48 -0.218%
cmd/go/internal/modget.s 38478 38398 -80 -0.208%
cmd/go/internal/modcmd.s 46430 46229 -201 -0.433%
cmd/go/internal/test.s 64399 64374 -25 -0.039%
cmd/compile/internal/ssa.s 3615264 3608276 -6988 -0.193%
cmd/compile/internal/gc.s 1538865 1537625 -1240 -0.081%
cmd/compile/internal/amd64.s 33593 33574 -19 -0.057%
cmd/compile/internal/x86.s 30871 30852 -19 -0.062%
total 19343565 19311284 -32281 -0.167%
Change-Id: Ib030eb79458827a5a5b6d0d2f98765f8325a4d7e
Reviewed-on: https://go-review.googlesource.com/c/go/+/222923
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
18 lines
368 B
Go
18 lines
368 B
Go
// asmcheck
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// Copyright 2020 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package codegen
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func efaceExtract(e interface{}) int {
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// This should be compiled with only
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// a single conditional jump.
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// amd64:-"JMP"
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if x, ok := e.(int); ok {
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return x
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}
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return 0
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}
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