This was in response to a post-merge review comment in
golang.org/cl/185537

Change-Id: I866b3882c8e83bf1fef60115cff5d1c6a9863f09
Reviewed-on: https://go-review.googlesource.com/c/go/+/186319Reviewed-by: Andrew Bonventre <andybons@golang.org>

When walking filesystem paths to locate packages, we normally prune
out subdirectories with names beginning with ".", "_", or equal to
"testdata". However, we should not prune out such a directory if it is
at or above the module root, since its name is not part of the package
path.

Fixes #28481
Updates #27852

Change-Id: Ice82b1f908afaab50f5592f6c38ca6a0fe911edf
Reviewed-on: https://go-review.googlesource.com/c/go/+/196297
Run-TryBot: Bryan C. Mills <bcmills@google.com>
Reviewed-by: Daniel Martí <mvdan@mvdan.cc>
Reviewed-by: Jay Conrod <jayconrod@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Change-Id: I1ab0b5f713581b5f497878f222fa4ba3998a0ccd
Reviewed-on: https://go-review.googlesource.com/c/go/+/196179Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

The current msanwrite() segfaults during libpreinit
when built with -msan on arm64. The cause is msancall()
in runtime/msan_arm64.s called by msanwrite() assumes
that it is always called with a valid g, leading to a
segfult.

This CL adds a check for nil g in msancall().

Fixes #34338

Change-Id: If4ad7e37556cd1d99346c1a7b4852651d1e4e4aa
Reviewed-on: https://go-review.googlesource.com/c/go/+/196157Reviewed-by: Cherry Zhang <cherryyz@google.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Fixes #34358

Change-Id: I3022ac88e1ad595dc72c0063852b8d4a1ec3f0ba
Reviewed-on: https://go-review.googlesource.com/c/go/+/196120
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Bryan C. Mills <bcmills@google.com>

Since I first started on this CL, most of the methods have had examples
added by other folks, so this is now one new example, and additions to
two existing examples for extra clarity.

The issue has a comment about not necessarily having examples for all
methods, but I recall finding this package pretty confusing when I first
used it, and having concrete examples would have really helped me
navigate all the different options. There are more
String methods with examples now, but I think seeing how the byte-slice
methods work could also be helpful to explain the differences.

Updates #21450

Change-Id: I27b4eeb634fb8ab59f791c0961cce79a67889826
Reviewed-on: https://go-review.googlesource.com/c/go/+/120145Reviewed-by: Daniel Martí <mvdan@mvdan.cc>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Currently, if you call various reflect methods you might get a panic with a
message like, "reflect: Field of non-struct type". Sometimes it's easy to
grok what's going on, but other times you need to laboriously go perform
reflect.ValueOf(myType).Kind().

This CL just adds that detail to the error message, saving debuggers the
extra step and making the error message more clear.

Change-Id: I7e0c211a3001e6b217b828cbcf50518080b5cb1e
Reviewed-on: https://go-review.googlesource.com/c/go/+/183097Reviewed-by: Daniel Martí <mvdan@mvdan.cc>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

'go tool trace' pointed at an obvious inefficiency; roughly the first
fifth of the program's life was CPU-heavy and making use of only one CPU
core at a time.

This was due to genOp being run before genLower. We did make genLower
use goroutines to parallelize the work between architectures, but we
didn't make genOp run in parallel too.

Do that. To avoid having two layers of goroutines, simply fire off all
goroutines from the main function, and inline genLower, since it now
becomes just two lines of code.

Overall, this shaves another ~300ms from 'go run *.go' on my laptop.

	name     old time/op         new time/op         delta
	Rulegen          2.04s ± 2%          1.76s ± 2%  -13.93%  (p=0.008 n=5+5)

	name     old user-time/op    new user-time/op    delta
	Rulegen          9.04s ± 1%          9.25s ± 1%   +2.37%  (p=0.008 n=5+5)

	name     old sys-time/op     new sys-time/op     delta
	Rulegen          235ms ±14%          245ms ±16%     ~     (p=0.690 n=5+5)

	name     old peak-RSS-bytes  new peak-RSS-bytes  delta
	Rulegen          179MB ± 1%          190MB ± 2%   +6.21%  (p=0.008 n=5+5)

Change-Id: I057e074c592afe06c831b03ca447fba12005e6f6
Reviewed-on: https://go-review.googlesource.com/c/go/+/196177
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Fixes #33185

Change-Id: I0adcffa5d1c9e55ae52309c59f961b0710166098
Reviewed-on: https://go-review.googlesource.com/c/go/+/187921Reviewed-by: Sameer Ajmani <sameer@golang.org>
Run-TryBot: Sameer Ajmani <sameer@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Currently, the line table reader keeps the file name table internal.
However, there are various attributes like AttrDeclFile and
AttrCallFile whose value is an index into this table. Hence, in order
to interpret these attributes, we need access to the file name table.

This CL adds a method to LineReader that exposes the file table of the
current compilation unit in order to allow consumers to interpret
attributes that index into this table.

Change-Id: I6b64b815f23b3b0695036ddabe1a67c3954867dd
Reviewed-on: https://go-review.googlesource.com/c/go/+/192699
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Than McIntosh <thanm@google.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

Currently, dwarf.Reader exposes the current compilation unit's address
size, but doesn't expose its byte order. Both are important for
decoding many attributes. For example, location descriptions include
addresses that are encoded in native form for the CU.

This CL exposes the byte order of the compilation unit in the same way
we already expose its address size, which makes it possible to decode
attributes containing native addresses.

Change-Id: I92f156818fe92b049d1dfc1613816bb1689cfadf
Reviewed-on: https://go-review.googlesource.com/c/go/+/192698
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

CL 140357 caused HTTP/2 connections to be put in the idle pool, but
failed to properly guard the trace.GotConn call in getConn. dialConn
returns a minimal persistConn with conn == nil for HTTP/2 connections.
This persistConn was then returned from queueForIdleConn and caused the
httptrace.GotConnInfo passed into GotConn to have a nil Conn field.

HTTP/2 connections call GotConn themselves so leave it for HTTP/2 to call
GotConn as is done directly below.

Fixes #34282

Change-Id: If54bfaf6edb14f5391463f908efbef5bb8a5d78e
GitHub-Last-Rev: 2b7d66a1ce66b4424c4d0fca2b8e8b547d874136
GitHub-Pull-Request: golang/go#34283
Reviewed-on: https://go-review.googlesource.com/c/go/+/195237Reviewed-by: Michael Fraenkel <michael.fraenkel@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Fix bug in previous CL 171768 -- with Go 1.13 the proper entry point
to call is runtime.setmodinfo, not runtime..z2fdebug.setmodinfo (this
changed when we moved from 1.12). [ Unclear why trybots and runs of
all.bash didn't catch this, but hand testing made it apparent. ]

Updates #30344.

Change-Id: I91f47bd0c279ad2d84875051be582818b13735b6
Reviewed-on: https://go-review.googlesource.com/c/go/+/196237
Run-TryBot: Than McIntosh <thanm@google.com>
Reviewed-by: Bryan C. Mills <bcmills@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

I noticed lots of trailing whitespace in one of cmd/trace's HTML files.
While at it, remove a few others from still-maintained files. Leave old
documents alone, such as doc/devel/weekly.html.

Change-Id: I7de7bbb6dd3fe6403bbb1f1178a8d3640c1e537b
Reviewed-on: https://go-review.googlesource.com/c/go/+/196178
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

RELNOTE=This change adds an underscore to all Go symbols in darwin, and
the behavior might be confusing to users of tools like "nm", etc.

Fixes #33808

Change-Id: I1849e6618c81215cb9bfa62b678f6f389cd009d5
Reviewed-on: https://go-review.googlesource.com/c/go/+/196217
Run-TryBot: Jeremy Faller <jeremy@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>

Use a different recipe for capturing debug modinfo if we're compiling
with the gccgo toolchain, to avoid applying a go:linkname directive to
a variable (not supported by gccgo).

Fixes #30344.

Change-Id: I9ce3d42c3bbb809fd68b140f56f9bbe3406c351b
Reviewed-on: https://go-review.googlesource.com/c/go/+/171768Reviewed-by: Bryan C. Mills <bcmills@google.com>
Run-TryBot: Bryan C. Mills <bcmills@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

This cleans up the isel code generation in ssa for ppc64x.

Current there is no isel op and the isel code is only
generated from pseudo ops in ppc64/ssa.go, and only using
operands with values 0 or 1. When the isel is generated,
there is always a load of 1 into the temp register before it.

This change implements the isel op so it can be used in PPC64.rules,
and can recognize operand values other than 0 or 1. This also
eliminates the forced load of 1, so it will be loaded only if
needed.

This will make the isel code generation consistent with other ops,
and allow future rule changes that can take advantage of having
a more general purpose isel rule.

Change-Id: I363e1dbd3f7f5dfecb53187ad51cce409a8d1f8d
Reviewed-on: https://go-review.googlesource.com/c/go/+/195057
Run-TryBot: Lynn Boger <laboger@linux.vnet.ibm.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Carlos Eduardo Seo <cseo@linux.vnet.ibm.com>

Fixes #32162

Change-Id: I164665108fa8ae299229054bded82cb3b027bccb
Reviewed-on: https://go-review.googlesource.com/c/go/+/196023
Run-TryBot: Bryan C. Mills <bcmills@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

Fixes #34015

Change-Id: I29798fb9c72b6f4bee8aecea96ab13b4cba2e80d
Reviewed-on: https://go-review.googlesource.com/c/go/+/195738
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

When compiling expression switches, we try to optimize runs of
constants into binary searches. The ordering used isn't visible to the
application, so it's unimportant as long as we're consistent between
sorting and searching.

For strings, it's much cheaper to compare string lengths than strings
themselves, so instead of ordering strings by "si <= sj", we currently
order them by "len(si) < len(sj) || len(si) == len(sj) && si <= sj"
(i.e., the lexicographical ordering on the 2-tuple (len(s), s)).

However, it's also somewhat cheaper to compare strings for equality
(i.e., ==) than for ordering (i.e., <=). And if there were two or
three string constants of the same length in a switch statement, we
might unnecessarily emit ordering comparisons.

For example, given:

    switch s {
    case "", "1", "2", "3": // ordered by length then content
        goto L
    }

we currently compile this as:

    if len(s) < 1 || len(s) == 1 && s <= "1" {
        if s == "" { goto L }
        else if s == "1" { goto L }
    } else {
        if s == "2" { goto L }
        else if s == "3" { goto L }
    }

This CL switches to using a 2-level binary search---first on len(s),
then on s itself---so that string ordering comparisons are only needed
when there are 4 or more strings of the same length. (4 being the
cut-off for when using binary search is actually worthwhile.)

So the above switch instead now compiles to:

    if len(s) == 0 {
        if s == "" { goto L }
    } else if len(s) == 1 {
        if s == "1" { goto L }
        else if s == "2" { goto L }
        else if s == "3" { goto L }
    }

which is better optimized by walk and SSA. (Notably, because there are
only two distinct lengths and no more than three strings of any
particular length, this example ends up falling back to simply using
linear search.)

Test case by khr@ from CL 195138.

Fixes #33934.

Change-Id: I8eeebcaf7e26343223be5f443d6a97a0daf84f07
Reviewed-on: https://go-review.googlesource.com/c/go/+/195340
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>

Fixes #34343.

Change-Id: I74240c8f431f6596338633a86a7a5ee1fce70a65
Reviewed-on: https://go-review.googlesource.com/c/go/+/196057
Run-TryBot: Robert Griesemer <gri@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

Remove redundant code and improve documentation in the process.

Fixes #34211.

Change-Id: I9a6d1467f1a2c98a163f41f9df147fc6500c6fad
Reviewed-on: https://go-review.googlesource.com/c/go/+/196077Reviewed-by: Ian Lance Taylor <iant@golang.org>

Change-Id: Ic33dfccf06681470bec19f66653fda67d9901095
Reviewed-on: https://go-review.googlesource.com/c/go/+/196118Reviewed-by: Keith Randall <khr@golang.org>

We used to use OXCASE to represent general, possibly multi-valued
cases, and then desugar these during walk into single-value cases
represented by OCASE.

In CL 194660, we switched to eliminated the desugaring step and
instead handle the multi-valued cases directly, which eliminates the
need for an OCASE Op. Instead, we can simply remove OCASE, and rename
OXCASE to just OCASE.

Passes toolstash-check.

Change-Id: I3cc184340f9081d37453927cca1c059267fdbc12
Reviewed-on: https://go-review.googlesource.com/c/go/+/196117Reviewed-by: Keith Randall <khr@golang.org>

When emitting base cases, previously we would emit:

    if c1 { s1 }
    if c2 { s2 }
    if c3 { s3 }

With this CL, we instead emit:

    if c1 { s1 }
    else if c2 { s2 }
    else if c3 { s3 }

Most of the time, this doesn't make a difference, because s1/s2/s3 are
typically "goto" statements. But for type switches, we currently emit:

    if hash == 271 { if _, ok := iface.(T1); ok { goto t1case } }
    if hash == 314 { if _, ok := iface.(T2); ok { goto t2case } }

That is, the if bodies can fallthrough, even though it's impossible
for them to match any of the subsequent cases.

Change-Id: I453d424d0b5e40060a703738bbb374523f1c403c
Reviewed-on: https://go-review.googlesource.com/c/go/+/195339
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>

Complete interfaces before comparing them with Checker.identical.
This requires passing through a *Checker to various functions that
didn't need this before.

Verified that none of the exported API entry points for interfaces
that rely on completed interfaces are used internally except for
Interface.Empty. Verified that interfaces are complete before
calling Empty on them, and added a dynamic check in the exported
functions.

Unfortunately, this fix exposed another problem with an esoteric
test case (#33656) which we need to reopen.

Fixes #34151.
Updates #33656.

Change-Id: I4e14bae3df74a2c21b565c24fdd07135f22e11c0
Reviewed-on: https://go-review.googlesource.com/c/go/+/195837
Run-TryBot: Robert Griesemer <gri@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>

Change-Id: I95921a8a55b243600aaec24ddca74b7040107dca
Reviewed-on: https://go-review.googlesource.com/c/go/+/195203Reviewed-by: Robert Griesemer <gri@golang.org>

This reverts commit 06e5529e.

Reason for revert: darwin_386 is unhappy. (Almost as unhappy as I am.)

https://build.golang.org/log/292c90a4ef1c93597b865ab8513b66a95d93d022

Change-Id: I690566ce1d8212317fc3dc349ad0d4d5a2bb58eb
Reviewed-on: https://go-review.googlesource.com/c/go/+/196033Reviewed-by: Cherry Zhang <cherryyz@google.com>
Run-TryBot: Cherry Zhang <cherryyz@google.com>

This change adds testable examples for the new Microseconds and Milliseconds methods that were introduced in Go 1.13.

Fixes #34354

Change-Id: Ibdbfd770ca2192f9086f756918325f7327ce0482
GitHub-Last-Rev: 4575f48f5feb8e49742304d17776e28302647931
GitHub-Pull-Request: golang/go#34355
Reviewed-on: https://go-review.googlesource.com/c/go/+/195979Reviewed-by: Alexander Rakoczy <alex@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Alexander Rakoczy <alex@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

RELNOTE=This change adds an underscore to all Go symbols in darwin, and
the behavior might be confusing to users of tools like "nm", etc.

Fixes #33808

Change-Id: I19ad626026ccae1e87b3bb97b6bb9fd55e95e121
Reviewed-on: https://go-review.googlesource.com/c/go/+/195619
Run-TryBot: Jeremy Faller <jeremy@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>

The elf reader's method for reading in DWARF section data has support
for applying selected relocations when the debug/dwarf readers are
being used on relocatable objects. This patch extends the set of
relocations applied slightly. In particlar, prior to this for some
architectures we were only applying relocations whose target symbol
was a section symbol; now we also include some relocations that target
other symbols. This is needed to get meaningful values for compilation
unit DIE low_pc attributes, which typically target a specific function
symbol in text.

Fixes #31363.

Change-Id: I34b02e7904cd7f2dea74197f73fa648141d15212
Reviewed-on: https://go-review.googlesource.com/c/go/+/195679Reviewed-by: Ian Lance Taylor <iant@golang.org>

As correctly pointed out by Giovanni Bajo, doing a single regexp pass
should be much faster than doing hundreds per architecture. We can then
use a map to keep track of what ops are handled in each file. And the
amount of saved work is evident:

	name     old time/op         new time/op         delta
	Rulegen          2.48s ± 1%          2.02s ± 1%  -18.44%  (p=0.008 n=5+5)

	name     old user-time/op    new user-time/op    delta
	Rulegen          10.9s ± 1%           8.9s ± 0%  -18.27%  (p=0.008 n=5+5)

	name     old sys-time/op     new sys-time/op     delta
	Rulegen          209ms ±28%          236ms ±18%     ~     (p=0.310 n=5+5)

	name     old peak-RSS-bytes  new peak-RSS-bytes  delta
	Rulegen          178MB ± 3%          176MB ± 3%     ~     (p=0.548 n=5+5)

The speed-up is so large that we don't need to parallelize it anymore;
the numbers above are with the removed goroutines. Adding them back in
doesn't improve performance noticeably at all:

	name     old time/op         new time/op         delta
	Rulegen          2.02s ± 1%          2.01s ± 1%   ~     (p=0.421 n=5+5)

	name     old user-time/op    new user-time/op    delta
	Rulegen          8.90s ± 0%          8.96s ± 1%   ~     (p=0.095 n=5+5)

While at it, remove an unused method.

Change-Id: I328b56e63b64a9ab48147e67e7d5a385c795ec54
Reviewed-on: https://go-review.googlesource.com/c/go/+/195739
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>

golang.org/cl/109517 optimized the compiler to avoid the allocation for make in
append(x, make([]T, y)...). This was only implemented for the case that y has type int.

This change extends the optimization to trigger for all integer types where the value
is known at compile time to fit into an int.

name             old time/op    new time/op    delta
ExtendInt-12        106ns ± 4%     106ns ± 0%      ~     (p=0.351 n=10+6)
ExtendUint64-12    1.03µs ± 5%    0.10µs ± 4%   -90.01%  (p=0.000 n=9+10)

name             old alloc/op   new alloc/op   delta
ExtendInt-12        0.00B          0.00B           ~     (all equal)
ExtendUint64-12    13.6kB ± 0%     0.0kB       -100.00%  (p=0.000 n=10+10)

name             old allocs/op  new allocs/op  delta
ExtendInt-12         0.00           0.00           ~     (all equal)
ExtendUint64-12      1.00 ± 0%      0.00       -100.00%  (p=0.000 n=10+10)

Updates #29785

Change-Id: Ief7760097c285abd591712da98c5b02bc3961fcd
Reviewed-on: https://go-review.googlesource.com/c/go/+/182559
Run-TryBot: Cuong Manh Le <cuong.manhle.vn@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>

Now that mid-stack inlining reports backtraces correctly, we no
longer need to protect against inlining in a few critical areas.

Update #19348
Update #28640
Update #34276

Change-Id: Ie68487e6482c3a9509ecf7ecbbd40fe43cee8381
Reviewed-on: https://go-review.googlesource.com/c/go/+/195818Reviewed-by: David Chase <drchase@google.com>

This slightly simplified the code. I stumbled upon this when support was
being added to Fuchsia (and this pattern was initially cargo-culted).

Change-Id: Ica090a118a0056c5c1b51697691bc7308f0d424a
Reviewed-on: https://go-review.googlesource.com/c/go/+/177878Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Add support for assembling integer computational instructions.

Based on the riscv-go port.

Updates #27532

Change-Id: Ibf02649eebd65ce96002a9ca0624266d96def2cd
Reviewed-on: https://go-review.googlesource.com/c/go/+/195079
Run-TryBot: Joel Sing <joel@sing.id.au>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>

This eliminates an old TODO.

Change-Id: I36d666905f43252f5d338b11ef9c1ed8b5f22b1f
Reviewed-on: https://go-review.googlesource.com/c/go/+/195817
Run-TryBot: Robert Griesemer <gri@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

There are a lot of complexities to handling switches efficiently:

1. Order matters for expression switches with non-constant cases and
for type expressions with interface types. We have to respect
side-effects, and we also can't allow later cases to accidentally take
precedence over earlier cases.

2. For runs of integers, floats, and string constants in expression
switches or runs of concrete types in type switches, we want to emit
efficient binary searches.

3. For runs of consecutive integers in expression switches, we want to
collapse them into range comparisons.

4. For binary searches of strings, we want to compare by length first,
because that's more efficient and we don't need to respect any
particular ordering.

5. For "switch true { ... }" and "switch false { ... }", we want to
optimize "case x:" as simply "if x" or "if !x", respectively, unless x
is interface-typed.

The current swt.go code reflects how these constraints have been
incrementally added over time, with each of them being handled ad
hocly in different parts of the code. Also, the existing code tries
very hard to reuse logic between expression and type switches, even
though the similarities are very superficial.

This CL rewrites switch handling to better abstract away the logic
involved in constructing the binary searches. In particular, it's
intended to make further optimizations to switch dispatch much easier.

It also eliminates the need for both OXCASE and OCASE ops, and a
subsequent CL can collapse the two.

Passes toolstash-check.

Change-Id: Ifcd1e56f81f858117a412971d82e98abe7c4481f
Reviewed-on: https://go-review.googlesource.com/c/go/+/194660
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>

This CL expands the test for #29612 to check that type switches also
work correctly when type hashes collide.

Change-Id: Ia153743e6ea0736c1a33191acfe4d8ba890be527
Reviewed-on: https://go-review.googlesource.com/c/go/+/195782
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Unmarshaling a string into a json.Number should first check that the string is a valid Number.
If not, we should fail without decoding it.

Fixes #14702

Change-Id: I286178e93df74ad63c0a852c3f3489577072cf47
GitHub-Last-Rev: fe69bb68eed06d056639f440d2daf4bb7c99013b
GitHub-Pull-Request: golang/go#34272
Reviewed-on: https://go-review.googlesource.com/c/go/+/195045Reviewed-by: Daniel Martí <mvdan@mvdan.cc>
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gobot Gobot <gobot@golang.org>