Adds:
GOEXPERIMENT=loopvar (expected way of invoking)
-d=loopvar={-1,0,1,2,11,12} (for per-package control and/or logging)
-d=loopvarhash=... (for hash debugging)
loopvar=11,12 are for testing, benchmarking, and debugging.
If enabled,for loops of the form `for x,y := range thing`, if x and/or
y are addressed or captured by a closure, are transformed by renaming
x/y to a temporary and prepending an assignment to the body of the
loop x := tmp_x. This changes the loop semantics by making each
iteration's instance of x be distinct from the others (currently they
are all aliased, and when this matters, it is almost always a bug).
3-range with captured iteration variables are also transformed,
though it is a more complex transformation.
"Optimized" to do a simpler transformation for
3-clause for where the increment is empty.
(Prior optimization of address-taking under Return disabled, because
it was incorrect; returns can have loops for children. Restored in
a later CL.)
Includes support for -d=loopvarhash=<binary string> intended for use
with hash search and GOCOMPILEDEBUG=loopvarhash=<binary string>
(use `gossahash -e loopvarhash command-that-fails`).
Minor feature upgrades to hash-triggered features; clients can specify
that file-position hashes use only the most-inline position, and/or that
they use only the basenames of source files (not the full directory path).
Most-inlined is the right choice for debugging loop-iteration change
once the semantics are linked to the package across inlining; basename-only
makes it tractable to write tests (which, otherwise, depend on the full
pathname of the source file and thus vary).
Updates #57969.
Change-Id: I180a51a3f8d4173f6210c861f10de23de8a1b1db
Reviewed-on: https://go-review.googlesource.com/c/go/+/411904
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Run-TryBot: David Chase <drchase@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
When deciding whether a captured variable can be passed by value, the
compiler is sensitive to the order that the OCLOSURE node is
typechecked relative to the order that the variable is passed to
"checkassign". Today, for an assignment like:
q, g = 2, func() int { return q }
we get this right because we always typecheck the full RHS expression
list before calling checkassign on any LHS expression.
But I nearly made a change that would interleave this ordering,
causing us to call checkassign on q before typechecking the function
literal. And alarmingly, there weren't any tests that caught this.
So this commit adds one.
Change-Id: I66cacd61066c7a229070861a7d973bcc434904cc
Reviewed-on: https://go-review.googlesource.com/c/go/+/280998
Trust: Matthew Dempsky <mdempsky@google.com>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Use the following (suboptimal) script to obtain a list of possible
typos:
#!/usr/bin/env sh
set -x
git ls-files |\
grep -e '\.\(c\|cc\|go\)$' |\
xargs -n 1\
awk\
'/\/\// { gsub(/.*\/\//, ""); print; } /\/\*/, /\*\// { gsub(/.*\/\*/, ""); gsub(/\*\/.*/, ""); }' |\
hunspell -d en_US -l |\
grep '^[[:upper:]]\{0,1\}[[:lower:]]\{1,\}$' |\
grep -v -e '^.\{1,4\}$' -e '^.\{16,\}$' |\
sort -f |\
uniq -c |\
awk '$1 == 1 { print $2; }'
Then, go through the results manually and fix the most obvious typos in
the non-vendored code.
Change-Id: I3cb5830a176850e1a0584b8a40b47bde7b260eae
Reviewed-on: https://go-review.googlesource.com/c/go/+/193848
Reviewed-by: Robert Griesemer <gri@golang.org>
Kindly detected by race builders by failing TestRaceRange.
ORANGE typecheck does not increment decldepth around body.
Change-Id: I0df5f310cb3370a904c94d9647a9cf0f15729075
Reviewed-on: https://go-review.googlesource.com/3507
Reviewed-by: Russ Cox <rsc@golang.org>
cmd/go doesn't complain (this is an open issue), but go/types does
Change-Id: I2caec1f7aec991a9500d2c3504c29e4ab718c138
Reviewed-on: https://go-review.googlesource.com/3541
Reviewed-by: Alan Donovan <adonovan@google.com>
Language specification says that variables are captured by reference.
And that is what gc compiler does. However, in lots of cases it is
possible to capture variables by value under the hood without
affecting visible behavior of programs. For example, consider
the following typical pattern:
func (o *Obj) requestMany(urls []string) []Result {
wg := new(sync.WaitGroup)
wg.Add(len(urls))
res := make([]Result, len(urls))
for i := range urls {
i := i
go func() {
res[i] = o.requestOne(urls[i])
wg.Done()
}()
}
wg.Wait()
return res
}
Currently o, wg, res, and i are captured by reference causing 3+len(urls)
allocations (e.g. PPARAM o is promoted to PPARAMREF and moved to heap).
But all of them can be captured by value without changing behavior.
This change implements simple strategy for capturing by value:
if a captured variable is not addrtaken and never assigned to,
then it is captured by value (it is effectively const).
This simple strategy turned out to be very effective:
~80% of all captures in std lib are turned into value captures.
The remaining 20% are mostly in defers and non-escaping closures,
that is, they do not cause allocations anyway.
benchmark old allocs new allocs delta
BenchmarkCompressedZipGarbage 153 126 -17.65%
BenchmarkEncodeDigitsSpeed1e4 91 69 -24.18%
BenchmarkEncodeDigitsSpeed1e5 178 129 -27.53%
BenchmarkEncodeDigitsSpeed1e6 1510 1051 -30.40%
BenchmarkEncodeDigitsDefault1e4 100 75 -25.00%
BenchmarkEncodeDigitsDefault1e5 193 139 -27.98%
BenchmarkEncodeDigitsDefault1e6 1420 985 -30.63%
BenchmarkEncodeDigitsCompress1e4 100 75 -25.00%
BenchmarkEncodeDigitsCompress1e5 193 139 -27.98%
BenchmarkEncodeDigitsCompress1e6 1420 985 -30.63%
BenchmarkEncodeTwainSpeed1e4 109 81 -25.69%
BenchmarkEncodeTwainSpeed1e5 211 151 -28.44%
BenchmarkEncodeTwainSpeed1e6 1588 1097 -30.92%
BenchmarkEncodeTwainDefault1e4 103 77 -25.24%
BenchmarkEncodeTwainDefault1e5 199 143 -28.14%
BenchmarkEncodeTwainDefault1e6 1324 917 -30.74%
BenchmarkEncodeTwainCompress1e4 103 77 -25.24%
BenchmarkEncodeTwainCompress1e5 190 137 -27.89%
BenchmarkEncodeTwainCompress1e6 1327 919 -30.75%
BenchmarkConcurrentDBExec 16223 16220 -0.02%
BenchmarkConcurrentStmtQuery 17687 16182 -8.51%
BenchmarkConcurrentStmtExec 5191 5186 -0.10%
BenchmarkConcurrentTxQuery 17665 17661 -0.02%
BenchmarkConcurrentTxExec 15154 15150 -0.03%
BenchmarkConcurrentTxStmtQuery 17661 16157 -8.52%
BenchmarkConcurrentTxStmtExec 3677 3673 -0.11%
BenchmarkConcurrentRandom 14000 13614 -2.76%
BenchmarkManyConcurrentQueries 25 22 -12.00%
BenchmarkDecodeComplex128Slice 318 252 -20.75%
BenchmarkDecodeFloat64Slice 318 252 -20.75%
BenchmarkDecodeInt32Slice 318 252 -20.75%
BenchmarkDecodeStringSlice 2318 2252 -2.85%
BenchmarkDecode 11 8 -27.27%
BenchmarkEncodeGray 64 56 -12.50%
BenchmarkEncodeNRGBOpaque 64 56 -12.50%
BenchmarkEncodeNRGBA 67 58 -13.43%
BenchmarkEncodePaletted 68 60 -11.76%
BenchmarkEncodeRGBOpaque 64 56 -12.50%
BenchmarkGoLookupIP 153 139 -9.15%
BenchmarkGoLookupIPNoSuchHost 508 466 -8.27%
BenchmarkGoLookupIPWithBrokenNameServer 245 226 -7.76%
BenchmarkClientServer 62 59 -4.84%
BenchmarkClientServerParallel4 62 59 -4.84%
BenchmarkClientServerParallel64 62 59 -4.84%
BenchmarkClientServerParallelTLS4 79 76 -3.80%
BenchmarkClientServerParallelTLS64 112 109 -2.68%
BenchmarkCreateGoroutinesCapture 10 6 -40.00%
BenchmarkAfterFunc 1006 1005 -0.10%
Fixes#6632.
Change-Id: I0cd51e4d356331d7f3c5f447669080cd19b0d2ca
Reviewed-on: https://go-review.googlesource.com/3166
Reviewed-by: Russ Cox <rsc@golang.org>
