While investigating the differences between 19710 (remove
tautological controls) and 12960 (bounds and nil propagation)
I observed that part of the wins of 19710 come from missed
opportunities for deadcode elimination due to phis.
See for example runtime.stackcacherelease. 19710 happens much
later than 12960 and has more chances to eliminate bounds.

Size of pkg/tool/linux_amd64/* excluding compile:

-this -12960 95882248
+this -12960 95880120
-this +12960 95581512
+this +12960 95555224

This change saves about 25k.

Change-Id: Id2f4e55fc92b71595842ce493c3ed527d424fe0e
Reviewed-on: https://go-review.googlesource.com/19728Reviewed-by: David Chase <drchase@google.com>
Run-TryBot: Alexandru Moșoi <alexandru@mosoi.ro>
TryBot-Result: Gobot Gobot <gobot@golang.org>

The upper bits of 8/16/32 bit constants are undefined.  We need to
truncate in order to prevent x86.oclass misidentifying the size of the
constant.

Fixes #14389

Change-Id: I3e5ff79cd904376572a93f489ba7e152a5cb6e60
Reviewed-on: https://go-review.googlesource.com/19740Reviewed-by: Keith Randall <khr@golang.org>

Loads of stores from the same pointer with compatible types
can be replaced with a copy.

Change-Id: I514b3ed8e5b6a9c432946880eac67a51b1607932
Reviewed-on: https://go-review.googlesource.com/19743
Run-TryBot: Todd Neal <todd@tneal.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>

Replaced comparison based on (*Type).String() with an
allocation-free structural comparison.  Roughly doubles
speed of CSE, also reduces allocations.

Checked that roughly the same number of CSEs were detected
during make.bash (about a million) and that "new" CSEs
were caused by the effect described above.

Change-Id: Id205a9f6986efd518043e12d651f0b01206aeb1b
Reviewed-on: https://go-review.googlesource.com/19471Reviewed-by: Keith Randall <khr@golang.org>

* If a operation is commutative order the parameters
in a canonical way.

Size of pkg/tool/linux_amd64/* excluding compile:
before: 95882288
 after: 95868152
change: 14136 ~0.015%

I tried something similar with Leq and Geq, but the results were
not great because it confuses the 'lowered cse' pass too much
which can no longer remove redundant comparisons from IsInBounds.

Change-Id: I2f928663a11320bfc51c7fa47e384b7411c420ba
Reviewed-on: https://go-review.googlesource.com/19727Reviewed-by: Keith Randall <khr@golang.org>
Run-TryBot: Alexandru Moșoi <alexandru@mosoi.ro>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Spotted a minor source of excess allocation in the register
allocator.  Rearranged the dominator tree code to pull its
scratch memory from a reused buffer attached to Config.

Change-Id: I6da6e7b112f7d3eb1fd00c58faa8214cdea44e38
Reviewed-on: https://go-review.googlesource.com/19450Reviewed-by: Keith Randall <khr@golang.org>
Run-TryBot: David Chase <drchase@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Add an initial cse pass that only operates on zero argument
values.  This removes the need for a special case in cse for removing
OpSB and speeds up arithConst_ssa.go compilation by 9% while slowing
"test -c net/http" by 1.5%.

Change-Id: Id1500482485426f66c6c2eba75eeaf4f19c8a889
Reviewed-on: https://go-review.googlesource.com/19454
Run-TryBot: Todd Neal <todd@tneal.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>

This adds a test case with aliased pointers to ensure modifications to
dse don't remove valid stores.

Change-Id: I143653250f46a403835218ec685bcd336d5087ef
Reviewed-on: https://go-review.googlesource.com/19795Reviewed-by: Keith Randall <khr@golang.org>

Change-Id: Idd880cc6c1e5dc34dddbdea0841a7a718d2fa836
Reviewed-on: https://go-review.googlesource.com/19544Reviewed-by: David Chase <drchase@google.com>

Change-Id: I731722eb77f373ff7d6101f93830ab0a50497e2c
Reviewed-on: https://go-review.googlesource.com/19542
Run-TryBot: David Chase <drchase@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>

Tested it 1000x on OS X and Linux amd64, no failures.
Updated TODO.

Change-Id: Ia60c8d90962f6e5f7c3ed1ded6ba1b25eee983e1
Reviewed-on: https://go-review.googlesource.com/19662Reviewed-by: Todd Neal <todd@tneal.org>

Also throw in a few more shift constant folding.

Change-Id: Iabe00596987f594e0686fbac3d76376d94612340
Reviewed-on: https://go-review.googlesource.com/19543
Run-TryBot: David Chase <drchase@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>

* In cases where we end up with empty branches like in
if a then jmp b else jmp b;
the flow can be replaced by a; jmp b.

The following functions is optimized as follows:
func f(a bool, x int) int {
        v := 0
        if a {
                v = -1
        } else {
                v = -1
        }
        return x | v
}

Before this change:
02819 (arith_ssa.go:362)  VARDEF "".~r2+16(FP)
02820 (arith_ssa.go:362)  MOVQ  $0, "".~r2+16(FP)
02821 (arith_ssa.go:362)  MOVB  "".a(FP), AX
02822 (arith_ssa.go:362)  TESTB AX, AX
02823 (arith_ssa.go:364)  JEQ 2824
02824 (arith_ssa.go:369)  VARDEF "".~r2+16(FP)
02825 (arith_ssa.go:369)  MOVQ  $-1, "".~r2+16(FP)
02826 (arith_ssa.go:369)  RET

After this change:
02819 (arith_ssa.go:362)  VARDEF "".~r2+16(FP)
02820 (arith_ssa.go:369)  VARDEF "".~r2+16(FP)
02821 (arith_ssa.go:369)  MOVQ  $-1, "".~r2+16(FP)
02822 (arith_ssa.go:369)  RET

Updates #14277

Change-Id: Ibe7d284f43406c704903632a4fcf2a4a64059686
Reviewed-on: https://go-review.googlesource.com/19464Reviewed-by: Keith Randall <khr@golang.org>
Run-TryBot: Alexandru Moșoi <alexandru@mosoi.ro>
TryBot-Result: Gobot Gobot <gobot@golang.org>

* Merge copyelim into phielim.
* Add phielimValue to rewrite. cgoIsGoPointer is, for example, 2
instructions smaller now.

Change-Id: I8baeb206d1b3ef8aba4a6e3bcdc432959bcae2d5
Reviewed-on: https://go-review.googlesource.com/19462Reviewed-by: David Chase <drchase@google.com>

ANDs of constants whose only set bits are leading or trailing can be
rewritten as two shifts instead.  This is slightly faster for 32 or
64 bit operands.

Change-Id: Id5c1ff27e5a4df22fac67b03b9bddb944871145d
Reviewed-on: https://go-review.googlesource.com/19485
Run-TryBot: Todd Neal <todd@tneal.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>

When printing a value with just an aux, print the aux as well. Debugging
cse is easier when the aux values are visible.

Change-Id: Ifaf96bdb25462c9df7ba01fdfdbf0d379631f555
Reviewed-on: https://go-review.googlesource.com/19476Reviewed-by: Keith Randall <khr@golang.org>

Flagalloc was recalculating flags is some situations
when it didn't need to.  Fixed by using the same name
for the original flag calculation instruction throughout.

Change-Id: Ic0bf58f728a8d87748434dd25a67b0708755e1f8
Reviewed-on: https://go-review.googlesource.com/19237
Run-TryBot: Keith Randall <khr@golang.org>
Reviewed-by: David Chase <drchase@google.com>

Semi-regular merge from tip to dev.ssa.

Two fixes:
1) Mark selectgo as not returning.  This caused problems
   because there are no VARKILL ops on the selectgo path,
   causing things to be marked live that shouldn't be.
2) Tell the amd64 assembler that addressing modes like
   name(SP)(AX*4) are ok.

Change-Id: I9ca81c76391b1a65cc47edc8610c70ff1a621913

Found by inspecting random generated code.

Change-Id: I57d0fed7c3a8dc91fd13cdccb4819101f9976ec9
Reviewed-on: https://go-review.googlesource.com/19413Reviewed-by: Keith Randall <khr@golang.org>

* Phis can have variable number of arguments, but rulegen assumed that
each operation has fixed number of arguments.
* Rewriting Phis is necessary to handle the following case:

func f1_ssa(a bool, x int) int {
        v := 0
        if a {
                v = -1
        } else {
                v = -1
        }
        return x|v
}

Change-Id: Iff6bd411b854f3d1d6d3ce21934bf566757094f2
Reviewed-on: https://go-review.googlesource.com/19412Reviewed-by: Keith Randall <khr@golang.org>

A first pass to decompose user types (structs, maybe
arrays someday), and a second pass to decompose builtin
types (strings, interfaces, slices, complex).  David wants
this for value range analysis so he can have structs decomposed
but slices and friends will still be intact and he can deduce
things like the length of a slice is >= 0.

Change-Id: Ia2300d07663329b51ed6270cfed21d31980daa7c
Reviewed-on: https://go-review.googlesource.com/19340
Run-TryBot: David Chase <drchase@google.com>
Reviewed-by: David Chase <drchase@google.com>

Adds a test to detect the bug that slipped in earlier when partioning
by the Aux value, but not sorting by it.

Change-Id: I56d0ba76383bbc1514b3dabd295e369771c26645
Reviewed-on: https://go-review.googlesource.com/19382
Run-TryBot: Todd Neal <todd@tneal.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>

ListenAndServeTLS doesn't require cert and key file names if the
server's TLSConfig has a cert configured. This code was never updated
when the GetCertificate hook was added to *tls.Config, however.

Fixes #14268

Change-Id: Ib282ebb05697edd37ed8ff105972cbd1176d900b
Reviewed-on: https://go-review.googlesource.com/19381Reviewed-by: Russ Cox <rsc@golang.org>

Fixes #14262.

Change-Id: Id590995dd4460e81f6b91bcfb3f02515a97650fe
Reviewed-on: https://go-review.googlesource.com/19361
Run-TryBot: Robert Griesemer <gri@golang.org>
Reviewed-by: Alan Donovan <adonovan@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Fixes #14259

Change-Id: I23fedec0eb85ae28e56bc24539bc864674856130
Reviewed-on: https://go-review.googlesource.com/19318Reviewed-by: Ian Lance Taylor <iant@golang.org>

INC/DEC produces slightly faster and smaller code.

Change-Id: I329d9bdb01b90041be45e053d9df640818bf0c2d
Reviewed-on: https://go-review.googlesource.com/19238
Run-TryBot: Ilya Tocar <ilya.tocar@intel.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>

Change-Id: Id51e5c97e9653b764b809bf3424f1a6d31b6ffea
Reviewed-on: https://go-review.googlesource.com/19338
Run-TryBot: David Chase <drchase@google.com>
Reviewed-by: David Chase <drchase@google.com>

Problem was caused by use of Args[].Aux differences
in early partitioning.  This artificially separated
two equivalent expressions because sort ignores the
Aux field, hence things can end with equal things
separated by unequal things and thus the equal things
are split into more than one partition.  For example:
SliceLen(a), SliceLen(b), SliceLen(a).

Fix: don't use Args[].Aux in initial partitioning.

Left in a debugging flag and some debugging Fprintf's;
not sure if that is house style or not.  We'll probably
want to be more systematic in our naming conventions,
e.g. ssa.cse, ssa.scc, etc.

Change-Id: Ib1412539cc30d91ea542c0ac7b2f9b504108ca7f
Reviewed-on: https://go-review.googlesource.com/19316Reviewed-by: Keith Randall <khr@golang.org>

The operation where this manifested in a crash was % (only defined on integers).
However, the existing code was sloppy in that it didn't retain the integer form
after a value (e.g., 3.0) was accepted as representable in integer form (3 for
the example). We would have seen a crash in such cases for / as well except
that there was code to fix it for just that case.

Remove the special code for / and fix more generally by retaining the integer
form for all operations if applicable.

Fixes #14229.

Change-Id: I8bef769e6299839fade27c6e8b5ff29ad6521d0d
Reviewed-on: https://go-review.googlesource.com/19300Reviewed-by: Alan Donovan <adonovan@google.com>

Examine both Aux and AuxInt to form more precise initial partitions.
Restructure loop to avoid repeated type.Equal() call.  Speeds up
compilation of testdata/gen/arithConst_ssa by 25%.

Change-Id: I3cfb1d254adf0601ee69239e1885b0cf2a23575b
Reviewed-on: https://go-review.googlesource.com/19313
Run-TryBot: Todd Neal <todd@tneal.org>
Reviewed-by: Keith Randall <khr@golang.org>

Panic doesn't return, so record that we immediately exit after a panic
call.  This will help code analysis.

Change-Id: I4d1f67494f97b6aee130c43ff4e44307b2b0f149
Reviewed-on: https://go-review.googlesource.com/19303
Run-TryBot: Keith Randall <khr@golang.org>
Reviewed-by: David Chase <drchase@google.com>

Change-Id: I630d4d2d8a914d6c07f22351a56d5e44a937123e
Reviewed-on: https://go-review.googlesource.com/19245Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

The test sends two HTTP/1.1 pipelined requests.  The first is
completedly by the second, and as such triggers an immediate call to the
CloseNotify channel.  The second calls the CloseNotify channel after the
overall connection is closed.

The test was passing fine on gc because the code would enter the select
loop before running the handler, so the send on gotReq would always be
seen first.  On gccgo the code would sometimes enter the select loop
after the handler had already finished, meaning that the select could
choose between gotReq and sawClose.  If it picked sawClose, it would
never close the overall connection, and the httptest server would hang.
The same hang could be induced with gc by adding a time.Sleep
immediately before the select loop.

Deflake the test by 1) don't close the overall connection until both
requests have been seen; 2) don't exit the loop until both closes have
been seen.

Fixes #14231.

Change-Id: I9d20c309125422ce60ac545f78bcfa337aec1c7d
Reviewed-on: https://go-review.googlesource.com/19281Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

The frontend does this for 32 bits and below, but SSA needs
to do it for 64 bits.  The algorithms are all copied from
cgen.go:cgen_div.

Speeds up TimeFormat substantially: ~40% slower to ~10% slower.

Change-Id: I023ea2eb6040df98ccd9105e15ca6ea695610a7a
Reviewed-on: https://go-review.googlesource.com/19302
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Todd Neal <todd@tneal.org>

Change-Id: I93201fa4152f2d60b3eedb8d321a152819033121
Reviewed-on: https://go-review.googlesource.com/19270Reviewed-by: Ian Lance Taylor <iant@golang.org>

Use just a single write barrier flag test, even if there
are multiple pointer fields in a struct.

This helps move more of the wb-specific code (like the LEA
needed to materialize the write address) into the unlikely path.

Change-Id: Ic7a67145904369c4ff031e464d51267d71281c8f
Reviewed-on: https://go-review.googlesource.com/19085
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>

Updates x/net/http2 to git rev 493a262 for https://golang.org/cl/19223

Fixes #14227

Change-Id: I626122811138fb3d88e4eea83f8da3fdcf91e0dc
Reviewed-on: https://go-review.googlesource.com/19250Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Change-Id: Ifb8eba1929c79ee7a8cae2191613c55a3b8f74e5
Reviewed-on: https://go-review.googlesource.com/19236Reviewed-by: Todd Neal <todd@tneal.org>

Updates #14227

Change-Id: If39f11471ecd307c9483f64e73f9c89fe906ae71
Reviewed-on: https://go-review.googlesource.com/19222Reviewed-by: Andrew Gerrand <adg@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>