Updates #6163
Fixes #24808

Change-Id: I4f5c686ebf60f72f71f566199ee3e946076202bb
Reviewed-on: https://go-review.googlesource.com/110439
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Change-Id: I573172384eaf32daaca5021a9a1874bf0f3d340f
Reviewed-on: https://go-review.googlesource.com/110575Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

The recent improvements to the prove pass
make it possible to provide bounds
hints to the compiler in some bvec routines.

This speeds up the compilation of the code in

name  old time/op       new time/op       delta
Pkg         7.93s ± 4%        7.69s ± 3%  -2.98%  (p=0.000 n=29+26)

While we're here, clean up some C-isms.

Updates #13554
Updates #20393

Change-Id: I47a0ec68543a9fc95c5359c3f37813fb529cb4f0
Reviewed-on: https://go-review.googlesource.com/110560
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>

This is the scanstack analog of CL 104737,
which made a similar change for copystack.

name         old time/op  new time/op  delta
ScanStack-8  41.1ms ± 6%  38.9ms ± 5%  -5.52%  (p=0.000 n=50+48)

Change-Id: I7427151dea2895ed3934f8a0f61d96b568019217
Reviewed-on: https://go-review.googlesource.com/105536
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Austin Clements <austin@google.com>

There are many possible stack scanning benchmarks,
but this one is at least a start.

cpuprofiling shows about 75% of CPU in func scanstack.

Change-Id: I906b0493966f2165c1920636c4e057d16d6447e0
Reviewed-on: https://go-review.googlesource.com/105535
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Austin Clements <austin@google.com>

Pick the low-hanging fruit, which are the gotos that don't go very far
and labels that aren't used often. All of them have easy replacements
with breaks and returns.

One slightly tricky rewrite is defaultlitreuse. We cannot use a defer
func to reset lineno, because one of its return paths does not reset
lineno, and thus broke toolstash -cmp.

Passes toolstash -cmp on std cmd.

Change-Id: Id1c0967868d69bb073addc7c5c3017ca91ff966f
Reviewed-on: https://go-review.googlesource.com/110063
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>

It was skipping dirs starting with ".", but it was missing the "_"
prefix and the "testdata" name. From "go help packages":

	Directory and file names that begin with "." or "_" are ignored
	by the go tool, as are directories named "testdata".

Before the change:

	$ go doc z # using src/cmd/go/testdata/testvendor/src/q/z
	package z // import "."

After the fix, it falls back to the current directory, as expected when
a single argument isn't found as a package in $GOPATH.

TestMain needs a small adjustment to keep the tests working, as now
their use of cmd/doc/testdata would normally not work.

This is the second try for this fix; the first time around, we included
cmd/doc/testdata to the dirs list by sending it to the channel via a
goroutine. However, that can end up in a send to a closed channel, if
GOROOT is a very small directory tree or missing.

To avoid that possibility, include the extra directory by pre-populating
the paths list, before the walking of GOROOT and GOPATH actually starts.

Fixes #24462.

Change-Id: I3b95b6431578e0d5cbb8342f305debc4ccb5f656
Reviewed-on: https://go-review.googlesource.com/109216
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Elias Naur <elias.naur@gmail.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

Passes toolstash -cmp on std cmd.

Change-Id: I17b9a816752af55b064b8e46146b8f5a878fa560
Reviewed-on: https://go-review.googlesource.com/109075
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>

Update #17490

Change-Id: Ia0bb0ba10dc0bbb299290a60b8228275d55125d7
Reviewed-on: https://go-review.googlesource.com/110438
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

Moving mmap, munmap, madvise, usleep.

Also introduce __error function to get at libc's errno variable.

Change-Id: Ic47ac1d9eb71c64ba2668ce304644dd7e5bdfb5a
Reviewed-on: https://go-review.googlesource.com/110437
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

Make selectgo return recvOK as a result parameter instead.

Change-Id: Iffd436371d360bf666b76d4d7503e7c3037a9f1d
Reviewed-on: https://go-review.googlesource.com/37935Reviewed-by: Austin Clements <austin@google.com>

Registration now looks like:

        var cases [4]runtime.scases
        var order [8]uint16
	cases[0].kind = caseSend
	cases[0].c = c1
	cases[0].elem = &v1
	if raceenabled || msanenabled {
		selectsetpc(&cases[0])
	}
	cases[1].kind = caseRecv
	cases[1].c = c2
	cases[1].elem = &v2
	if raceenabled || msanenabled {
		selectsetpc(&cases[1])
	}
	...

Change-Id: Ib9bcf426a4797fe4bfd8152ca9e6e08e39a70b48
Reviewed-on: https://go-review.googlesource.com/37934
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Austin Clements <austin@google.com>

Now the registration phase looks like:

    var cases [4]runtime.scases
    var order [8]uint16
    selectsend(&cases[0], c1, &v1)
    selectrecv(&cases[1], c2, &v2, nil)
    selectrecv(&cases[2], c3, &v3, &ok)
    selectdefault(&cases[3])
    chosen := selectgo(&cases[0], &order[0], 4)

Primarily, this is just preparation for having the compiler open-code
selectsend, selectrecv, and selectdefault.

As a minor benefit, order can now be layed out separately on the stack
in the pointer-free segment, so it won't take up space in the
function's stack pointer maps.

Change-Id: I5552ba594201efd31fcb40084da20b42ea569a45
Reviewed-on: https://go-review.googlesource.com/37933
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Austin Clements <austin@google.com>

Fixes #25143

Change-Id: Ide654fe70651fda827cdeeaaa73d2a1f8aefd7e7
Reviewed-on: https://go-review.googlesource.com/110159Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Convert raise from raw syscalls to using the system pthread library.
As a bonus, raise will now target the current thread instead of the
process.

Updates #17490

Change-Id: I2e44f2000bf870e99a5b4dc5ff5e0799fba91bde
Reviewed-on: https://go-review.googlesource.com/110475
Run-TryBot: Elias Naur <elias.naur@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>

Now we no longer need to mess with TLS on Darwin 386/amd64, we always
rely on the pthread library to set it up. We now just use one entry
in the TLS for the G.
Return from mstart to let the pthread library clean up the OS thread.

Change-Id: Iccf58049d545515d9b1d090b161f420e40ffd244
Reviewed-on: https://go-review.googlesource.com/110215Reviewed-by: Ian Lance Taylor <iant@golang.org>

Currently, there is no check for a negative modulus in ModInverse.
Negative moduli are passed internally to GCD, which returns 0 for
negative arguments. Mod is symmetric with respect to negative moduli,
so the calculation can be done by just negating the modulus before
passing the arguments to GCD.

Fixes #24949

Change-Id: Ifd1e64c9b2343f0489c04ab65504e73a623378c7
Reviewed-on: https://go-review.googlesource.com/108115Reviewed-by: Robert Griesemer <gri@golang.org>
Run-TryBot: Robert Griesemer <gri@golang.org>

Currently, the behavior of z.ModInverse(g, n) is undefined
when g and n are not relatively prime.  In that case, no
ModInverse exists which can be easily checked during the
computation of the ModInverse.  Because the ModInverse does
not indicate whether the inverse exists, there are reimplementations
of a "checked" ModInverse in crypto/rsa.  This change removes the
undefined behavior.  If the ModInverse does not exist, the receiver z
is unchanged and the return value is nil. This matches the behavior of
ModSqrt for the case where the square root does not exist.

name          old time/op    new time/op    delta
ModInverse-4    2.40µs ± 4%    2.22µs ± 0%   -7.74%  (p=0.016 n=5+4)

name          old alloc/op   new alloc/op   delta
ModInverse-4    1.36kB ± 0%    1.17kB ± 0%  -14.12%  (p=0.008 n=5+5)

name          old allocs/op  new allocs/op  delta
ModInverse-4      10.0 ± 0%       9.0 ± 0%  -10.00%  (p=0.008 n=5+5)

Fixes #24922

Change-Id: If7f9d491858450bdb00f1e317152f02493c9c8a8
Reviewed-on: https://go-review.googlesource.com/108996
Run-TryBot: Robert Griesemer <gri@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>

CL 93658 moved stack trace printing inside a systemstack call to
sidestep complexity in case the runtime is in a inconsistent state.

Unfortunately, debuggers generating backtraces for a Go panic
will be confused and come up with a technical correct but useless
stack. This CL moves just the crash performing - typically a SIGABRT
signal - outside the systemstack call to improve backtraces.

Unfortunately, the crash function now needs to be marked nosplit and
that triggers the no split stackoverflow check. To work around that,
split fatalpanic in two: fatalthrow for runtime.throw and fatalpanic for
runtime.gopanic. Only Go panics really needs crashes on the right stack
and there is enough stack for gopanic.

Example program:

package main

import "runtime/debug"

func main() {
	debug.SetTraceback("crash")
	crash()
}

func crash() {
	panic("panic!")
}

Before:
(lldb) bt
* thread #1, name = 'simple', stop reason = signal SIGABRT
  * frame #0: 0x000000000044ffe4 simple`runtime.raise at <autogenerated>:1
    frame #1: 0x0000000000438cfb simple`runtime.dieFromSignal(sig=<unavailable>) at signal_unix.go:424
    frame #2: 0x0000000000438ec9 simple`runtime.crash at signal_unix.go:525
    frame #3: 0x00000000004268f5 simple`runtime.dopanic_m(gp=<unavailable>, pc=<unavailable>, sp=<unavailable>) at panic.go:758
    frame #4: 0x000000000044bead simple`runtime.fatalpanic.func1 at panic.go:657
    frame #5: 0x000000000044d066 simple`runtime.systemstack at <autogenerated>:1
    frame #6: 0x000000000042a980 simple at proc.go:1094
    frame #7: 0x0000000000438ec9 simple`runtime.crash at signal_unix.go:525
    frame #8: 0x00000000004268f5 simple`runtime.dopanic_m(gp=<unavailable>, pc=<unavailable>, sp=<unavailable>) at panic.go:758
    frame #9: 0x000000000044bead simple`runtime.fatalpanic.func1 at panic.go:657
    frame #10: 0x000000000044d066 simple`runtime.systemstack at <autogenerated>:1
    frame #11: 0x000000000042a980 simple at proc.go:1094
    frame #12: 0x00000000004268f5 simple`runtime.dopanic_m(gp=<unavailable>, pc=<unavailable>, sp=<unavailable>) at panic.go:758
    frame #13: 0x000000000044bead simple`runtime.fatalpanic.func1 at panic.go:657
    frame #14: 0x000000000044d066 simple`runtime.systemstack at <autogenerated>:1
    frame #15: 0x000000000042a980 simple at proc.go:1094
    frame #16: 0x000000000044bead simple`runtime.fatalpanic.func1 at panic.go:657
    frame #17: 0x000000000044d066 simple`runtime.systemstack at <autogenerated>:1

After:
(lldb) bt
* thread #7, stop reason = signal SIGABRT
  * frame #0: 0x0000000000450024 simple`runtime.raise at <autogenerated>:1
    frame #1: 0x0000000000438d1b simple`runtime.dieFromSignal(sig=<unavailable>) at signal_unix.go:424
    frame #2: 0x0000000000438ee9 simple`runtime.crash at signal_unix.go:525
    frame #3: 0x00000000004264e3 simple`runtime.fatalpanic(msgs=<unavailable>) at panic.go:664
    frame #4: 0x0000000000425f1b simple`runtime.gopanic(e=<unavailable>) at panic.go:537
    frame #5: 0x0000000000470c62 simple`main.crash at simple.go:11
    frame #6: 0x0000000000470c00 simple`main.main at simple.go:6
    frame #7: 0x0000000000427be7 simple`runtime.main at proc.go:198
    frame #8: 0x000000000044ef91 simple`runtime.goexit at <autogenerated>:1

Updates #22716

Change-Id: Ib5fa35c13662c1dac2f1eac8b59c4a5824b98d92
Reviewed-on: https://go-review.googlesource.com/110065
Run-TryBot: Elias Naur <elias.naur@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Austin Clements <austin@google.com>

This change provides VZIP1, VZIP2, VTBL instruction for supporting
ChaCha20Poly1305 implementation later.

Change-Id: Ife7c87b8ab1a6495a444478eeb9d906ae4c5ffa9
Reviewed-on: https://go-review.googlesource.com/110015Reviewed-by: Cherry Zhang <cherryyz@google.com>
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

The general policy for the current state of js/wasm is that it only
has to support tests that are also supported by nacl.

The test nilptr3.go makes assumptions about which nil checks can be
removed. Since WebAssembly does not signal on reading a null pointer,
all nil checks have to be explicit.

Updates #18892

Change-Id: I06a687860b8d22ae26b1c391499c0f5183e4c485
Reviewed-on: https://go-review.googlesource.com/110096Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

When deciding whether to flush the constant pool, the distance check
in checkpool can fail to account for padding inserted before the next
instruction by nacl.

For example, see this failure:
https://go-review.googlesource.com/c/go/+/109350/2#message-07085b591227824bb1d646a7192cbfa7e0b97066
Here, the pool should be flushed before a CALL instruction, but
checkpool only considers the CALL instruction to be 4 bytes and
doesn't account for the 8 extra bytes of alignment padding added
before it by asmoutnacl. As a result, it flushes the pool after the
CALL instruction, which is 4 bytes too late.

Furthermore, there's no explanation for the rather convoluted
expression used to decide if we need to emit the constant pool.

This CL modifies checkpool to take the PC following the tentative
instruction as an argument. The caller knows this already and this way
checkpool doesn't have to guess (and get it wrong in the presence of
padding). In the process, it rewrites the test to be structured and
commented.

Change-Id: I32a3d50ffb5a94d42be943e9bcd49036c7e9b95c
Reviewed-on: https://go-review.googlesource.com/110017
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>

This commit only moves code in preparation for the following commit
which adds the js/wasm architecture to the os package. There are no
semantic changes in this commit.

Updates #18892

Change-Id: Ia44484216f905c25395c565c34cfe6996c305ed6
Reviewed-on: https://go-review.googlesource.com/109976Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

It's also fewer system calls. Fall back to longer read
only if it seems like the Uname result is truncated.

Fixes #24701

Change-Id: Ib6550acede8dddaf184e8fa9de36377e17bbddab
Reviewed-on: https://go-review.googlesource.com/110295Reviewed-by: Ian Lance Taylor <iant@golang.org>

Change-Id: I84334dfd02ad9a27b3fb6d46a6b1c015a3f03511
Reviewed-on: https://go-review.googlesource.com/110335Reviewed-by: Filippo Valsorda <filippo@golang.org>

Change-Id: I9699b22d3a308cda685aa684b32dcde99333df46
Reviewed-on: https://go-review.googlesource.com/110315Reviewed-by: Filippo Valsorda <filippo@golang.org>

I was confused about how to start an HTTP server if the server
cert/key are in memory, not on disk. I thought it would be good to
show an example of how to use these two functions to accomplish that.

example-cert.pem and example-key.pem were generated using
crypto/tls/generate_cert.go.

Change-Id: I850e1282fb1c38aff8bd9aeb51988d21fe307584
Reviewed-on: https://go-review.googlesource.com/72252Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Even though GOARCH=riscv64 is not supported by gc yet, it is easy
to make cmd/cgo already support it.

Together with the changes in debug/elf in CL 107339 this e.g. allows
to generate Go type definitions for linux/riscv64 in the
golang.org/x/sys/unix package without using gccgo.

Change-Id: I6b849df2ddac56c8c483eb03d56009669ca36973
Reviewed-on: https://go-review.googlesource.com/110066
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

The iOS exec wrapper uses ios-deploy to set up a device, install
the wrapped app, and start a lldb session to run it. ios-deploy is
not built to be scripted, as can be seen from the brittle way it is
driven by the Go wrapper. There are many timeouts and comments such
as

"
// lldb tries to be clever with terminals.
// So we wrap it in script(1) and be clever
// right back at it.
"

This CL replaces the use of ios-deploy with a lldb driver script in
Python. lldb is designed to be scripted, so apart from getting rid
of the ios-deploy dependency, we gain:

- No timouts and scripting ios-deploy through stdin and parsing
stdout for responses.
- Accurate exit codes.
- Prompt exits when the wrapped binary fails for some reason. Before,
the go test timeout would kick in to fail the test.
- Support for environment variables.
- No noise in the test output. Only the test binary output is output
from the wrapper.

We have to do more work with the lldb driver: mounting the developer
image on the device, running idevicedebugserverproxy and installing
the app. Even so, the CL removes almost as many lines as it adds.
Furthermore, having the steps split up helps to tell setup errors
from runtime errors.

Change-Id: I48cccc32f475d17987283b2c93aacc3da18fe339
Reviewed-on: https://go-review.googlesource.com/107337
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Missed conversion of newosproc for the parts of darwin that
weren't affected by my previous change.

Update #25181

Change-Id: I81a2935e192b6d0df358c59b7e785eb03c504c23
Reviewed-on: https://go-review.googlesource.com/110123Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>

In the binary sizes FAQ, the approximate size of a Go hello world
binary was said to be 1.5MB (it was about 1.6MB on go1.7 on
linux/amd64). Sadly, this is no longer true. A Go1.10 hello world is
2.0MB, and in 1.11 it'll be about 2.5MB.

Just say "a couple megabytes" to stop this dance.

Change-Id: Ib4dc13a47ccd51327c1a9d90d4116f79597513a4
Reviewed-on: https://go-review.googlesource.com/110069Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Some of the comments relative paths do not exist and
reflect does not define its own hmap structure.

Correct paths and consistently reference paths starting from the
go src directory.

Change-Id: I5204a3a98f77d65f17dcde98b847378cea05ad8a
Reviewed-on: https://go-review.googlesource.com/94758
Run-TryBot: Martin Möhrmann <moehrmann@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>

Add a compiler intrinsic for getcallerpc on arm64 for better code generation.

Change-Id: I897e670a2b8ffa1a8c2fdc638f5b2c44bda26318
Reviewed-on: https://go-review.googlesource.com/109276Reviewed-by: Cherry Zhang <cherryyz@google.com>
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Replace thread creation with calls to the pthread
library in libc.

Update #17490

Change-Id: I1e19965c45255deb849b059231252fc6a7861d6c
Reviewed-on: https://go-review.googlesource.com/108679
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

Fixes ssacheck build.

Change-Id: Idf1d2ea9a971a1f17f2fca568099e870bb5d913f
Reviewed-on: https://go-review.googlesource.com/110122
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Austin Clements <austin@google.com>

and assign the same colors for spans belong to the tasks
(sadly, the trace viewer will change the saturation/ligthness
for asynchronous slices so exact color mapping is impossible.
But I hope they are not too far from each other)

Change-Id: Idaaf0828a1e0dac8012d336dcefa1c6572ddca2e
Reviewed-on: https://go-review.googlesource.com/109338
Run-TryBot: Hyang-Ah Hana Kim <hyangah@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Heschi Kreinick <heschi@google.com>

Change the help doc of

  go tool compile -d=ssa/help

from this:

  compile: GcFlag -d=ssa/<phase>/<flag>[=<value>|<function_name>]
  <phase> is one of:
  check, all, build, intrinsics, early_phielim, early_copyelim
  early_deadcode, short_circuit, decompose_user, opt, zero_arg_cse
  opt_deadcode, generic_cse, phiopt, nilcheckelim, prove, loopbce
  decompose_builtin, softfloat, late_opt, generic_deadcode, check_bce
  fuse, dse, writebarrier, insert_resched_checks, tighten, lower
  lowered_cse, elim_unread_autos, lowered_deadcode, checkLower
  late_phielim, late_copyelim, phi_tighten, late_deadcode, critical
  likelyadjust, layout, schedule, late_nilcheck, flagalloc, regalloc
  loop_rotate, stackframe, trim
  <flag> is one of on, off, debug, mem, time, test, stats, dump
  <value> defaults to 1
  <function_name> is required for "dump", specifies name of function to dump after <phase>
  Except for dump, output is directed to standard out; dump appears in a file.
  Phase "all" supports flags "time", "mem", and "dump".
  Phases "intrinsics" supports flags "on", "off", and "debug".
  Interpretation of the "debug" value depends on the phase.
  Dump files are named <phase>__<function_name>_<seq>.dump.

To this:

  compile: PhaseOptions usage:

      go tool compile -d=ssa/<phase>/<flag>[=<value>|<function_name>]

  where:

  - <phase> is one of:
      check, all, build, intrinsics, early_phielim, early_copyelim
      early_deadcode, short_circuit, decompose_user, opt, zero_arg_cse
      opt_deadcode, generic_cse, phiopt, nilcheckelim, prove
      decompose_builtin, softfloat, late_opt, generic_deadcode, check_bce
      branchelim, fuse, dse, writebarrier, insert_resched_checks, lower
      lowered_cse, elim_unread_autos, lowered_deadcode, checkLower
      late_phielim, late_copyelim, tighten, phi_tighten, late_deadcode
      critical, likelyadjust, layout, schedule, late_nilcheck, flagalloc
      regalloc, loop_rotate, stackframe, trim

  - <flag> is one of:
      on, off, debug, mem, time, test, stats, dump

  - <value> defaults to 1

  - <function_name> is required for the "dump" flag, and specifies the
    name of function to dump after <phase>

  Phase "all" supports flags "time", "mem", and "dump".
  Phase "intrinsics" supports flags "on", "off", and "debug".

  If the "dump" flag is specified, the output is written on a file named
  <phase>__<function_name>_<seq>.dump; otherwise it is directed to stdout.

Also add a few examples at the bottom.

Fixes #20349

Change-Id: I334799e951e7b27855b3ace5d2d966c4d6ec4cff
Reviewed-on: https://go-review.googlesource.com/110062Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>

The prove pass sometimes has bounds information
that later rewrite passes do not.

Use this information to mark shifts as bounded,
and then use that information to generate better code on amd64.
It may prove to be helpful on other architectures, too.

While here, coalesce the existing shift lowering rules.

This triggers 35 times building std+cmd. The full list is below.

Here's an example from runtime.heapBitsSetType:

			if nb < 8 {
				b |= uintptr(*p) << nb
				p = add1(p)
			} else {
				nb -= 8
			}

We now generate better code on amd64 for that left shift.

Updates #25087

vendor/golang_org/x/crypto/curve25519/mont25519_amd64.go:48:20: Proved Rsh8Ux64 bounded
runtime/mbitmap.go:1252:22: Proved Lsh64x64 bounded
runtime/mbitmap.go:1265:16: Proved Lsh64x64 bounded
runtime/mbitmap.go:1275:28: Proved Lsh64x64 bounded
runtime/mbitmap.go:1645:25: Proved Lsh64x64 bounded
runtime/mbitmap.go:1663:25: Proved Lsh64x64 bounded
runtime/mbitmap.go:1808:41: Proved Lsh64x64 bounded
runtime/mbitmap.go:1831:49: Proved Lsh64x64 bounded
syscall/route_bsd.go:227:23: Proved Lsh32x64 bounded
syscall/route_bsd.go:295:23: Proved Lsh32x64 bounded
syscall/route_darwin.go:40:23: Proved Lsh32x64 bounded
compress/bzip2/bzip2.go:384:26: Proved Lsh64x16 bounded
vendor/golang_org/x/net/route/address.go:370:14: Proved Lsh64x64 bounded
compress/flate/inflate.go:201:54: Proved Lsh64x64 bounded
math/big/prime.go:50:25: Proved Lsh64x64 bounded
vendor/golang_org/x/crypto/cryptobyte/asn1.go:464:43: Proved Lsh8x8 bounded
net/ip.go:87:21: Proved Rsh8Ux64 bounded
cmd/internal/goobj/read.go:267:23: Proved Lsh64x64 bounded
cmd/vendor/golang.org/x/arch/arm64/arm64asm/decode.go:534:27: Proved Lsh32x32 bounded
cmd/vendor/golang.org/x/arch/arm64/arm64asm/decode.go:544:27: Proved Lsh32x32 bounded
cmd/internal/obj/arm/asm5.go:1044:16: Proved Lsh32x64 bounded
cmd/internal/obj/arm/asm5.go:1065:10: Proved Lsh32x32 bounded
cmd/internal/obj/mips/obj0.go:1311:21: Proved Lsh32x64 bounded
cmd/compile/internal/syntax/scanner.go:352:23: Proved Lsh64x64 bounded
go/types/expr.go:222:36: Proved Lsh64x64 bounded
crypto/x509/x509.go:1626:9: Proved Rsh8Ux64 bounded
cmd/link/internal/loadelf/ldelf.go:823:22: Proved Lsh8x64 bounded
net/http/h2_bundle.go:1470:17: Proved Lsh8x8 bounded
net/http/h2_bundle.go:1477:46: Proved Lsh8x8 bounded
net/http/h2_bundle.go:1481:31: Proved Lsh64x8 bounded
cmd/compile/internal/ssa/rewriteARM64.go:18759:17: Proved Lsh64x64 bounded
cmd/compile/internal/ssa/sparsemap.go:70:23: Proved Lsh32x64 bounded
cmd/compile/internal/ssa/sparsemap.go:73:45: Proved Lsh32x64 bounded

Change-Id: I58bb72f3e6f12f6ac69be633ea7222c245438142
Reviewed-on: https://go-review.googlesource.com/109776
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Giovanni Bajo <rasky@develer.com>

The motivation is avoid generating a pointer to the data being
converted so it can be garbage collected.
The change also slightly reduces binary size by shrinking call sites.

Fixes #24286

Benchmark results:
name                   old time/op  new time/op  delta
ConvT2ESmall-4         2.86ns ± 0%  2.80ns ± 1%  -2.12%  (p=0.000 n=29+28)
ConvT2EUintptr-4       2.88ns ± 1%  2.88ns ± 0%  -0.20%  (p=0.002 n=28+30)
ConvT2ELarge-4         19.6ns ± 0%  20.4ns ± 1%  +4.22%  (p=0.000 n=19+30)
ConvT2ISmall-4         3.01ns ± 0%  2.85ns ± 0%  -5.32%  (p=0.000 n=24+28)
ConvT2IUintptr-4       3.00ns ± 1%  2.87ns ± 0%  -4.44%  (p=0.000 n=29+25)
ConvT2ILarge-4         20.4ns ± 1%  21.3ns ± 1%  +4.41%  (p=0.000 n=30+26)
ConvT2Ezero/zero/16-4  2.84ns ± 1%  2.99ns ± 0%  +5.38%  (p=0.000 n=30+25)
ConvT2Ezero/zero/32-4  2.83ns ± 2%  3.00ns ± 0%  +5.91%  (p=0.004 n=27+3)

Change-Id: I65016ec94c53f97c52113121cab582d0c342b7a8
Reviewed-on: https://go-review.googlesource.com/102636Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

When a loop has bound len(s)-delta, findIndVar detected it and
returned len(s) as (conservative) upper bound. This little lie
allowed loopbce to drop bound checks.

It is obviously more generic to teach prove about relations like
x+d<w for non-constant "w"; we already handled the case for
constant "w", so we just want to learn that if d<0, then x+d<w
proves that x<w.

To be able to remove the code from findIndVar, we also need
to teach prove that len() and cap() are always non-negative.

This CL allows to prove 633 more checks in cmd+std. Most
of them are cases where the code was already testing before
accessing a slice but the compiler didn't know it. For instance,
take strings.HasSuffix:

    func HasSuffix(s, suffix string) bool {
        return len(s) >= len(suffix) && s[len(s)-len(suffix):] == suffix
    }

When suffix is a literal string, the compiler now understands
that the explicit check is enough to not emit a slice check.

I also found a loopbce test that was incorrectly
written to detect an overflow but had a off-by-one (on the
conservative side), so it unexpectly passed with this CL; I
changed it to really trigger the overflow as intended.

Change-Id: Ib5abade337db46b8811425afebad4719b6e46c4a
Reviewed-on: https://go-review.googlesource.com/105635
Run-TryBot: Giovanni Bajo <rasky@develer.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>